Home

life-cycle cost analysis for protection and rehabilitation

1. 58 xi Part II Figure 4 1 Figure 5 1 Figure 6 1 Figure 6 2 Figure 6 3 Figure 6 4 Figure 7 1 Figure 10 1 Figure 10 2 Figure 10 3 Figure 12 1 Figure 12 2 Figure 12 3 Figure 12 4 Figure 12 5 xii Tests Required 3726242400 4nesaescn Duros 39 RR AC OR ee ees 106 Nomogram to Determine Concrete Condition Index S 115 Nomogram to Determine Age of Concrete at Time to First Sign of Deterioration OR Cee ee ee re eee a 119 Conceptual Flowchart to Determine Concrete Performance Equation ee Quse pad dnd ee re E ee 120 Nomogram to Determine Parameter B in Concrete Performance Equation 2 5 2424 un e ened 122 Nomogram to Determine Parameter A in Concrete Performance Equation Zo 2x o9 RA XR RH e A 123 Concrete Performance Curves 132 141 Nomogram for User Costs During Treatment 157 158 Nomogram to Determine Increment in Travel Time Across Bridge uy y RE ES eaten d ach doe es eed 159 Nomogram to Determine User Costs Prior to Treatment 160 Trends of Corrosion Process After Treatment 164 165 Nomogram to Determine Effective Service Life of Concrete After Treatment When Rate of Corrosion Continues at the Same Rate eere 166 Chart to Find Age of Concrete at Time of First Corrosion 168 Nomogram to Determine Effective Service Life of Concrete After Treatment When Rate of Corrosion Incre
2. yes no Is the member exposed to marine environment Is the member within 25 ft 7 6m of seawater yes no Flowchart 8 Pre Deterioration Submodule continued o e 9 Use the following table to determine appropriate surface chloride value Snowfall range Distance from Surface chloride at 10 years inches seawater feet whichever is greater 0 3 Z t 10 or 0 04 3 12 Z t 10 t or 0 10 0 12 gt 25 Z t 10 t or 0 10 0 12 25 Z t 10 t or 0 25 gt 12 Z t 10 t or 0 25 gt 12 gt 25 Z t 10 t or 0 35 gt 12 lt 25 Z t 10 t or 0 45 o Import cover and water cement ratio from Protect Information Module Calculation One Submodule S 1 9 Calculation Two Submodule Fit these two points to the distress equation inchis 2 54 centimeters 1 foot is 0 305 meters 68 Flowchart 9 Calculation Two Submodule This module is required to estimate the condition at some time in the future after the time to deterioration by adjusting the slope of the distress curve The rate of distress will be dictated by many factors including the steel concentration oxygen availability and the resistivity of the concrete in the field All these factors are not known However an estimate of whether the deterioration rate will be low medium or high is possible and standard curves can be assigned to each rate designation This can be based on the wet resistivi
3. 58 50 I cO O2 t2 c O Figure 12 Difference of Traffic using overlay as example N High Traffic Low Traffic CHF HA 8 12 16 20 24 28 32 36 Time at Which Treatment Is Performed Years Appendix A Flowcharts 59 ma SEM A SS ipu ani Vu ias vmi sums pm sum vau isi ansa aa mmi mum me aaa um was m wa es quy i meer w em mel miss wak ME aaa ei ui n J Flowchart 1 General Technical Methodology for Technical Goal One GENERAL INFORMATION MODULE REPAIR Member Previously z Repaired y 2 v Calculate amp Use S at t no PROTECT INFORMATION MODULE PRESENT INFORMATION MODULE Calculate S at t me we FF ee ee TIME TO MODULE For previously repaired structure time to deterioration tp is replaced by time of POST DETERIORATION yes SUBMODULE repair t and condition after repair S_ replaces the t condition of 1 9 no PRE Calculation One DETERIORATION Submodule PM CDU yes IS lt 12 gt Define t at S 1 9 d Ignore S amp t no PRESENT INFORMATION Use present distress i M condition and present Calculate amp Use S at t time from present module Time to Distress is equal to AE Use S at t the present t
4. 18 Continued Concrete Performance Curves B Figure 7 1 c e co ce c c e e e oo m wO v lt en C1 S x pul uopIpuoo 20 40 50 60 Concrete Age Years t 10 136 Continued Concrete Performance Curves B 20 Figure 7 1 S xepuj uoprpuo Concrete Age Years t 137 25 ete Performance Curves B Figure 7 1 Continued Concr pcc s eee ress ee pas ae ES S Ne som ar Ga Ae h S a a A es EMEN RNa 2 ERE RUNE ER L po rox CR Ss a w T SS NCC Lo a y fa S A ee ey ew E PIN pepe SENI ee ee ae 138 ete Performance Curves B 30 Continued Concr 7 1 Figure 0 WO eA poc pq lt ANE emus UAN o T cec TE cem BEI un lll vu Co 0 O Q C 110 O 3X oO 3X o D O o c C 9 o0 tC eO Oe 139 s B 40 ete Performance Curve 7 1 Continued Concr Figure 140 Continued Concrete Performance Curves B 80 Figure 7 1 S xepuj uonipuoo Concrete Age Years t 141 8 Compatible Treatment Alternatives The following sections identify a range of treatment alternatives from which the selection can be made Generally there are two types of treatment deck treatment and structural treatment Structural treatment as defined here applies only to superstructure and substructure elements i e non deck elements A comprehensive description of concrete treatment alternatives is provided in SHRP
5. 2 Overview of the Handbook This chapter provides the user with an overview of the handbook and prepares the user for the details of the methodology that follow in the next 11 chapters Those 11 chapters i e Chapters 3 through 13 of the handbook provide a step by step procedure to lead the user to the appropriate treatment of a specific concrete component that is what type of treatment to apply and when to apply it for maximum cost effectiveness The answer is obtained by conducting the life cycle cost analyses found in Chapter 13 Chapters 3 through 12 are background chapters and provide the necessary information on service lives and costs that are input into Chapter 13 to conduct life cycle cost analyses Chapter 14 includes an example with calculations and illustrates how the methodology is applied to a realistic bridge component 2 1 How to Use the Handbook To use this handbook the user should first become familiar with the methodology by reviewing Chapters 3 through 13 Chapter 13 can then be used for any specific case to determine the most cost effective strategy In Chapter 13 references are systematically made to Chapter 3 through 12 to gather the input information required The next several pages outline and briefly discuss Chapters 3 through 13 2 2 Chapter 3 Service Life Limitation due to Functional Features This chapter addresses functional features of the bridge so that if the remaining service life of the whole structu
6. 8 5 S 7 1 C Prediction of Performance Chapter 6 Use Section 6 2 Concrete not Repaired Rehabilitated and or Protected Previously and without a Special Protection Step 1 t 1992 1978 14 years S 7 1 P Since S more than 1 9 use Steps 2 and 3 in Section 6 2 193 Step 2 Use Equation 6 2 or Figure 6 1 to find t concrete age at first sign of deterioration t 2 695 d 22 0 Z 042 pyjo t 2 695 1 4 1 282 x 0 50 x 14221 0 250 1 282 x 0 05 x 0 48 t 7 5 years and S 19 Step 3 Use Equations 6 4 and 6 5 to find Parameters B and A Alternatively use Figures 6 3 and 6 4 B In S 100 S S 100 S2 t t B In 1 9 100 7 1 7 1 100 1 9 7 5 14 B 021 A 100 S S exp Bt A 100 7 1 7 1 exp 0 21 x 14 A 2453 Thus the concrete performance equation is S 100 1 245 3 exp 0 21 t D Evaluation of Performance Chapter 7 Treatment Consideration Period t t Find t from Equation 7 2 or Figure 7 1 assuming S 35 tn In 100 Sm A S B ta In 100 35 245 3 x 35 0 21 194 ta 23 3 years and t 14 years Treatment Consideration Period 23 3 14 9 3 years i e 1992 to 2001 Use the rest of the handbook to determine the timing of the treatment within the treatment consideration period for a compatible treatment E Compatible Treatment Al
7. CL Glossary of Variables Percent of free flow travel time across bridge representing increment in travel time when deck condition is maximum tolerable Constant controlling rate of deterioration in concrete performance equation Constant controlling rate of deterioration in concrete performance equation Two way capacity of bridge during normal periods vehicles per day Two way capacity of bridge during construction vehicles per day Percent of concrete samples with bar level chlorides higher than corrosion threshold value Number of cement sacks per cubic yard of concrete Rate of corrosion of reinforcing steel when concrete condition is maximum tolerable Rate of corrosion of reinforcing steel measured at present corresponding to 90th percentile value average rate of corrosion plus 1 282 standard deviation Rate of corrosion of reinforcing steel at previous repair rehabilitation and or protection Rate of corrosion of reinforcing steel at the time of planned treatment COST DELAM DF DF EI ESL Cost of last cycle of treatment in planning horizon Depth of bar cover corresponding to 10th percentile value average depth minus 1 282 standard deviation The present worth factor Total deck area square feet Percent of concrete area that is delaminated not including spalls Discount factor Discount factor corresponding to Year 20 in planning horizon Effective interest rate Effec
8. 5 70 200 where t t ta 2 18 65 years ESL 5 18 65 5 18 65 5 70 ESL 14 years The year to the next cycle of treatment is 14 6 Year 20 Fill out those boxes in Columns 3 and 4 which correspond to Year 20 with S 35 and the type of treatment patch LSDC Find the approximate concrete condition index after treatment using Equation 13 1 Safer Treatment S Index just after Treatment x No of Years after Treatment Effective Service Life after Treatment Index just after Treatment Sater Treatment 35 10 3 x No of Years after Treatment 14 10 3 Safer Treatment 1 8 x No of Years after Treatment 10 3 No of Years After S After Treatment Year in Planning Horizon Treatment 1 12 1 7 2 13 9 8 3 15 7 9 4 17 5 10 5 19 3 11 6 21 1 12 7 22 9 13 8 24 7 14 9 26 5 15 10 28 3 16 11 30 1 17 12 31 9 18 13 33 7 19 14 35 20 Step 3 Agency Costs Fill out the appropriate boxes of Column 5 in Figure 13 1 with the cost associated with the application of the treatment see F above for itemized costs 201 Strategy Treat at t DELAM 5 SPALL 1 Total Area Deteriorated 5 1 6 1 Removing and patching concrete 6 percent of 10 000 square feet at 35 per square foot 21 000 2 Concrete overlay 10 000 square feet at 5 60 per square foot the total costs for scarifying the deck placing and curing the overlay and providing traffic control 56 000
9. Corrosion Analysis File Selection Once you have entered the corrosion analysis submenu CORRODE prompts you for the names of two files e Start with choose any previous corrosion file that you may have used for this bridge which you would like to use as a point of departure in the current analysis For example if you performed a corrosion analysis with CORRODE for the selected deck a year ago and you would now like to update those findings choose the file pertaining to that run If this is the first time you are analyzing a deck or you don t wish to select any of the previously defined files select the default e Results file the results of the current corrosion analysis will be stored in the file you identify here Choose a name that conforms to DOS naming conventions If the name you enter matches that of a previously defined corrosion file CORRODE will ask you OK to overwrite existing file If you respond no N CORRODE will return you to the entry field so that you may modify the name you had entered If you respond yes Y CORRODE will display the current contents of the existing file you have specified and the procedure from this point onward will be the same as if you were editing the existing file The results file will be assigned specifically to the selected bridge Thus it is possible to have corrosion files of the same name assigned to different bridges CORRODE regards these files as separate independent files and
10. User Costs 36 Agency Costs 53 The user cost is essentially 0 throughout the early part of the analysis indicating very few incremental costs because the deck is new and has no adverse impacts on speed and travel time Congestion costs due to the treatment project are negligible in all cases and for all years in this example because of the relatively short length of the bridge and the modest level of traffic This situation might change with longer spans in which travel time effects would become more significant or with detours around the bridge site Implications of higher traffic volumes are investigated later in the example Note that the user costs do not begin to affect the result until the bridge deck condition deteriorates to a condition bad enough to have a noticeable effect on traffic Furthermore the increase in user costs may occur at relatively low values of the condition index S taken over the entire deck area since distress is likely to be concentrated in the wheelpaths exhibiting much higher local values of S In effect therefore the incremental user costs act as an economic justification for bridge deck treatments Viewed another way the dramatically higher user costs attributable to worsening deck conditions are the penalties that drivers incur for deferred repair of a facility The optimal timing of the overlay treatment is obtained from the point of minimum total costs in Figure 10 which in this case is 24
11. 7 500 to 30 000 2 16 L23 Distress Rate percent index increase per year is calculated as follows Condition Index 1 9 Years to Condition Index t For example the distress rate for medium resistivity concrete is 45 19 _ 43 1 _ 51g Lt 2091 20 ESTIMATED ELECTRICAL RESISTIVITY OF CONCRETE MATERIALS Obtain three fully cured core or cylinder samples at least 4 inches 10 2 centimeters in diameter and 2 inches 5 1 centimeters long The samples shall be completely representative of the concrete to be studied Perform Rapid Permeability tests on each of the three samples in accordance with the procedure of AASHTO T277 83 Rapid Determination of the Chloride Permeability of Concrete except add the following Immediately prior to connection of the 60 volt power supply leads record the two pin AC resistance between the two cell halfs measured with a Nilsson 400 or equivalent Calculate estimated resistivity by multiplying the measured AC resistance by 16 8 Report the estimated resistivity 73 degrees F vacuum saturated for each specimen Average the findings for the three individual specimens and also report the average and the range 85 oouondxo uo poseq SIFE snoumgA SY 1oJ p l gurt s3 31e sT9A9 o puo uO e enns 9 ON 6 0C 6 OI 09 0 00S9 00 c 0 vl ce sl SE S 090 0089 00S0 I VI SC AVANSISOI MOT FL O 8S8I LS 6I LS 6 09 0 00 9 00 0 Vi SI c8 19 c8 9C 8C 0 00S 0001 0 VI 96 L6 96 CC 8c
12. Chapter 3 for selecting bridge file names 6 2 Reports Types of Reports CORRODE provides you several choices in the REPORTS submenu Corrosion analysis results a summary of the key data that you have entered and the results of the corrosion analysis The information displayed includes the bridge file name any comment you may have entered in BRIDGES general bridge characteristics results of the survey of deck distress rebar chloride values the current value of the distress index S estimated points of the deck s distress history the estimated time to deterioration t and the estimated deterioration function S e Life cycle cost analysis results a tabulation of the results of a single life cycle cost analysis for each year showing the computed agency cost user cost and total cost in thousands of dollars and identifying the optimal treatment time i e the year with the lowest life cycle cost These results apply to a single bridge the selected bridge and one treatment the results that are displayed are retrieved from a single life cycle cost file 263 Figure 7 Viewing Results Types of Reports Corrosion Analysis Results Life Cycle Cost Analysis Results Combined Life Cycle Cost Reports Reports Options Create View e Print Delete Types of Graphs Life Cycle Cost Graph Combined Life Cycle Cost Graph 264 e Combined life cycle cost reports a com
13. Electrica continuity of the reinforcing steel should be known prior to conducting certain tests or applying certain treatments Electrical continuity can be determined by measuring the resistance between widely separated steel components Low resistivities indicate continuity B 5 Chloride Profiles AASHTO 7260 84 or SHRP Modified Test Method This test determines the chloride content of concrete Concrete powdered samples are collected with a vacuum bit near the concrete surface 0 25 to 0 75 inch depth and at the level of the reinforcing steel the bottom 0 25 inch of concrete cover Where a concrete overlay is applied concrete surface is the surface of the overlay The SHRP Test Method for Field Determination of Total Chioride Content is documented in Appendix F of Cady and Gannon In the SHRP test method which is a field method the powdered samples are dissolved in and stabilized by two solutions A probe is then inserted into the mixture and the readings are recorded in the field Calculations convert readings into chloride content expressed as a percentage of concrete weight AASHTO T260 84 test method may also be used for chloride content determination B 6 Corrosion Potential Survey ASTM C876 This procedure ASTM C876 determines the potential for the existence of reinforcing steel corrosion by measuring the electrical potential of the reinforcing steel It may be performed if 10 percent of the chloride samples at the dep
14. Fill out Column 2 by starting with Year 1 in the first row i e 1 Step 2 Condition Index and Treatment Column 3 relates to concrete condition index Column 4 relates to the type and timing of the treatment Follow the procedures below for the three strategies considered 1 Treat at t Example in Figure 13 2 Find the concrete condition index at present Chapter 5 Fill out the first row of Column 3 with the condition index at present before treatment S 15 and the condition index at present after treatment 8 2 Fill out the first row of Column 4 with the type of treatment considered patch LSDC low slump dense concrete overlay Find the effective service life of the treated concrete ESL Chapter 12 15 years Find the year to the next cycle of treatment by adding one to the 180 Figure 13 1 Worksheet for Life Cycle Cost Bridge Name amp No Year Structure Built Bridge Length ft Two Way ADT amp Year Component for Treatment Component Area sq ft Initially Built with a Protection What Type Previously Repaired Rehabilitated and or Protected When amp What W C Ratio Cover Depth Avg amp S D in Electrical Continuity Year Tested Spalls Delams Bar Level CL gt Threshold Surface CL Avg amp S D Ib cy 181 Figure 13 1 Worksheet for Life Cycle Cost Continued o 3 4 6 7 8 10 Date Year Cond Treatment Agency User User Present
15. Index Type Cost Cost Cost Worth S Maint Prior During to Treat Treat PE EE _ ar NEUE ANE _ j J j ee NEM NN NN HE NI RUE FREE LLL LL ee MENS was EN ENS NEN RENE CE MEM DENE EN j J _ _ EMEN MM MEE _ NN Y MEE QUEM _ LLL HUE NN MU ME NE HN RNC G ee ee MEN NK ot O o j Lo NNI MER NN NRBEM ss TREE WE NEN NE J _ j _ J a eid D on Sour ane ee poires OD _ ma MEN ee NEM ee ee ee DNE MEE EN Total Present Worth Salvage Value Life Cycle Cost 182 Figure 13 2 Example of Tabulated Treatment Strategy Treat at t 1 Q 3 4 S 6 Date Year Cond Treatment Agency Agency Index Type Cost Cost S Initial Maint Patch y LSDC 8 9 10 User Discount Present Cost Factor Worth During Treat o o Lom Ne 0 790 1 274 n O Nw Nw 1 775 MM lam oss ET ans 0 600 4 072 sms 5 368 6 788 8 472 2007 46 666 Patch 214 033 LSDC I oss ta t3 be e p e e e 17 8 Total Present Worth 294 450 Salvage Value 82 380 Life Cycle Cost 212 070 183 Figure 13 3 Example of Tabulated Treatment Strategy Treat at t 7 9 User i Discount Cost Factor 1 2 3 4 Date Year Cond Treatment Index Type S 1 324 2 259 3 619 5 516 8 076 1 323 Patch LSDC
16. The SHRP test method is documented in Appendix B of Cady and Gannon If overlay debonding is significant the most cost effective treatment may be obtained considering factors which are not covered in this methodology Cover Depth over Reinforcement Using a Cover Meter Magnetic Flux Device This device uses a magnetic field to detect reinforcing steel within hardened concrete It can determine the location orientation size and depth of the bar The accuracy of the device in measuring the depth of cover decreases as the depth of cover increases Magnetic particles in the concrete can influence the measurements Thus a correction factor should be obtained by exposing the bar at one location and measuring the actual depth Usually the correction factor is obtained at a location which can later serve as the half cell test bar ground connection If the bar size is not known the depth cannot be read directly from the scale therefore the following technique is suggested 1 Locate the bar in the test area 2 Place a two by four or other non metallic spacer between the probe and the concrete surface 3 Record possible bar size and depth combinations 4 Correct readings for the thickness of the spacer by subtracting its thickness 109 5 Place the probe directly on the concrete surface and record possible reading The bar size for which the same cover depth is obtained in Steps 4 and 5 is the correct result Reinforcing
17. an existing overlay or a layer of the concrete is removed and replaced 3 When cathodic protection is used with a concrete overlay 4 May be applied on some concrete overlays 5 Rough concrete surface can puncture membranes unless a smooth concrete surface can be provided for the new membrane 6 Exceptions can exist 7 When slump is 4 5 inches 11 4 centimeters or more 232 Table 2 Selection of Compatible Structural Treatment Alternatives Technical Recast Preplaced Patch Shot Cathod Disadvantage Aggregate crete Protect Repair depth Not Not more than 2 Good Good inches Small area repair Not Good Internal Not vibration Good problem Experienced Not contractor not Good available Electricity not Not available Good Existing polymer Not injection repair Good in concrete 1 Shotcrete may be applied in several stages Reason Concrete consolidation and bonding can be a problem Mobilization not justified Concrete consolidation can be a problem Certain skills required Cathodic Protection need electricity Insulated bars 233 Figure 3 Treatment Menu Options Treatments Edit Treatments New Treatments Treatment Description File Name Comment Data Input Forms Cost and Productivity Data Estimated Life Effect of Treatment Effects on Traffic Adjustment Factors 234 Copy Treatment Copying a treatment
18. and the procedure from this point onward will be the same as if you had requested to edit an existing file e Note When you define a new treatment file just as when you edit an existing file it will be associated with the currently selected bridge If you wish the treatment to be associated with a bridge other than the one currently selected in the information bar at the bottom of the screen return to the BRIDGES menu and select the desired bridge before defining the treatment Refer to Chapter 3 on how to select a bridge file 4 4 Copying a Treatment File Many times you may wish to apply a given type of treatment to more than one bridge deck Ideally you would like to be able to define a treatment only once and then apply that information to any bridge deck for which the treatment may be applicable In practice however this time saving approach cannot be implemented so easily The reason is that the information that describes a treatment depends at least to some degree on the characteristics of the bridge deck in question For example the productivity and costs of a treatment may depend on the area of the deck and how many lanes can be closed at once to perform work These data also depend on when the estimate is made since both productivity and cost vary over time as a result of technological advances evolving legal requirements and standards of good practice and cost inflation 236 CORRODE provides a compromise between these
19. at its best performance or removal of all contaminated concrete and protection against further chloride intrusion The effective service life of the treated concrete in this case is theoretically infinite provided the protection is repeated periodically as needed to keep the concrete free of corrosion Case 2 Concrete Repaired Rehabilitated and or Protected Previously Case 2 applies to all concretes which were previously repaired rehabilitated and or protected and will be repaired rehabilitated and or protected again Use the following procedure to predict the effective service life of the treated concrete 171 TUE YEA ISA SIBI juouneo1y loyy YY S IAI9S APNA pIWAL JON SBM 9J9 9u02 JI qopipuoo o qu19 o wnwIxejy 0 our PUB uo solro SILI 0 om 994 98 SIVA oec st 9I PHI A OI 8 9 y 4 0 05 X I Sesua1 aq uotisoJ1407 Jo 33 wy Wag 3uasurusoJ 193JV 332942u0 JO JrI 921AJ9S 9A1 2329JJT 9uturi9joqp 01 WBIZOMION QZT in3L4 172 Step 1 Find t age of concrete at present years and C the rate of corrosion at present milli amperes per square foot C is the 90th percentile value i e average rate of corrosion plus 1 282 standard deviation Step 2 Find t age of concrete at the time of the previous repair rehabilitation and or protection years find C the rate of corrosion at the time of the previous repair rehabilitation and or protection milli amperes per square f
20. previously rehabilitated members as well as members which have never been rehabilitated for members presently showing physical distress and for members which are not yet salt contaminated or distressed 1 2 Technical Goal Two Decomposing Condition Index Technical Goal Two involves devising a means of decomposing the predicted concrete condition index into its distress component parts for the purpose of estimating the physical distress in the concrete in the future so that treatment cost estimates can be performed 13 Technical Goal Three Cost and Maximum Service Life of Treatment Technical Goal Three provides cost and service life information maximum possible life based on non corrosion related distress for alternative procedures for treatment of concrete 1 4 Technical Goal Four Condition Index Versus Time after Treatment Technical Goal Four supplies procedures to predict the condition index with time after each applicable treatment 11 1 5 Technical Goal Five Life Cycle Cost Analysis Technical Goal Five provides procedures to determine the treatment that results in the lowest life cycle cost as well as the optimum time to apply that treatment 1 6 Report Format This report discusses the technical goals of the methodology Flowcharts of various modules questions to the user and decisions are included in Appendix A They are helpful in understanding the discussion Although the technical basis and details are voluminous
21. 1 should be considered default values The user may adjust those values if desired As a concrete bridge component ages its condition gradually deteriorates and its condition index increases to a point where some type of treatment must be done The maximum tolerable condition index S will be selected by the user based on structural features of the component and or ride quality of the deck This handbook uses a concrete condition index of 35 as the maximum tolerable index for bridge deck treatment when ride quality is the criterion The index of 35 represents roughly 50 percent concrete deterioration based on Equation 5 1 see Chapter 11 114 Nomogram to Determine Concrete Condition Index S Figure 5 1 M NS 10 Concrete Condition Index S of Concrete Samples Chloride Contaminated CL 115 6 Prediction of Performance This chapter presents a systematic procedure for predicting the concrete condition index at any time in the future Site specific concrete condition data and concrete engineering properties are used for this purpose Three cases are distinguished for the prediction of performance on the basis of construction features as follows 1 Concrete repaired rehabilitated and or protected previously 2 Concrete not repaired rehabilitated and or protected previously and without a special protection built at the time of initial construction 3 Concrete not repaired rehabilitated and or prote
22. 27 9 18 35 11 8 ay B w tv 7 595 Patch LSDC 214 033 ba t tv t a e wo O eis S S J Total Present Worth 362 274 Salvage Value 86 499 Life Cycle Cost 275 774 184 Figure 13 4 Example of Tabulated Treatment Strategy Treat between t and t 1 2 3 4 S 6 Date Year Cond Treatment Agency Agency Index Type Cost Cost S Initial Maint tch 139 230 LSDC g Lan be p wo k I a Spem a MN CY NC o pem pL ND x 90 Patch 214 033 11 8 LSDC 2007 a G2 ig Total Present Worth 316 866 Salvage Value 72 083 Life Cycle Cost 244 782 185 186 effective service life of the treated concrete 1 15 Year 16 Fill out those boxes in Columns 3 and 4 which correspond to the year of next cycle of treatment Year 16 with the maximum tolerable condition index S 35 the condition index after treatment 11 8 use Chapter 11 to decompose S and Chapter 5 to determine the index just after treatment and the type of treatment in the next cycle of treatment patch LSDC Find the approximate concrete condition index for each consecutive year after the treatment from Equation 13 1 Fill out the appropriate boxes of Column 3 with the approximate condition indices determined 10 0 through 33 4 S dun S Index just after Treatment x No of Years after Treatment Effective Service Life after Treatment Index just after Treatm
23. 4 Maintenance costs only for monitoring and maintaining cathodic protection in this methodology 31 4 2 User Costs Two types of user costs are included in the methodology 1 during treatment costs 2 prior to treatment and subsequent to treatment costs During Treatment Costs Costs during the treatment are related to congestion as influenced by the degree of bridge closure and the duration of the construction Use Equation 4 1 to find user costs resulting from the degree of bridge closure U K t t q Eq 4 1 where U user costs during the treatment period dollars K value of bridge user time while traveling dollars per minute per vehicle t duration of treatment days q average two way daily traffic volume across the bridge vehicles per day t increment in travel time across the bridge or in detour around the bridge caused by construction minutes For traveling across the bridge t may be obtained from Equation 4 2 t 0 15 t q C1 a C Eq 4 2 where t free flow travel time across the bridge minutes 32 C1 two way capacity of the bridge during construction vehicles per day C two way capacity of the bridge during normal periods vehicles per day Prior to Treatment and Subsequent to Treatment Costs Decks Only Costs in the period prior to treatment are a function of the condition of the bridge deck and its effect on traffic flow A badly spalled deck would impede
24. 54 centimeters or thicker concrete jackets or shotcrete DELAM is 8 times SPALL For all non deck concrete with 1 inch 2 54 centimeters or thicker concrete jackets or shotcrete DELAM is 16 times SPALL 3 For all concrete bar level chloride contamination CL percent of total area increases linearly from 0 at condition index of 0 to 100 at condition index of 20 i e 5 percent CL increase for each index increase of 1 Bar level chloride contamination remains at 100 percent when the index is greater than 20 As an example assume a non overlay deck is predicted to have a condition index of 12 sometime in the future What will be the amount of total deterioration at that time CL is predicted to be 12 5 60 CL portion of the index is 60 8 5 7 06 Then DELAM SPALL portion of the index is 12 7 06 4 94 Or stated differently 4 94 2 5 DELAM 7 5 SPALL 8 5 Whereas for non overlay decks DELAM 4 SPALL This will give DELAM 9 60 and SPALL 2 40 29 Thus the total deterioration DELAM SPALL 9 60 2 40 12 00 Percent of deck area Although research would be required to completely validate the rules stated here they are technically logical and therefore meet the present need In the area of cost calculations the following point should also be considered The actual delaminations which exist and the concrete which is removed prior to patching are not equal This is because it is necessary to
25. A and B in the equation are found based on the site specific data To find the parameters two appropriate data points are required Each data point represents the condition index and the corresponding concrete age Because of the widely varying members and their past present and future conditions the two needed data points on the condition index versus time curve cannot always be at the same condition or age When possible one of the points will be the age of concrete at the initiation of deterioration t with an assigned condition index S and the other will be the age of concrete at the present t with the condition index at the present S As discussed previously the two terms representing the age of concrete at the initiation of corrosion and the start of physical distress are t and t respectively For the purposes of this effort the following condition indices were assigned to those items on the basis of experience 1 Condition index at t Sj 10 percent chloride contamination 0 percent delamination and 0 percent spalling Therefore S 1 2 14 Figure 2 Bridge Deck Deterioration Model a Typical in Literature Practical Maximum PO rrr rrr a m a a a a Condition Index S Time t b Assumed in this Study Practical Maximum Condition Index S T
26. BRIDGES option If the treatment will have no effect on traffic flow on the bridge you should make this value equal to the normal capacity you input in BRIDGES The congestion formula for use during treatment projects in CORRODE is qo qo D Si U ete CU Eq 4 1 where 243 U the increment in bridge user costs during the project period due to congestion caused by the treatment work zone in dollars per vehicle K the value of bridge user time while traveling expressed in dollars per minute per vehicle averaged over the daily traffic stream a aconstant with a default value of 0 15 t the free flow travel time across the bridge in minutes q the average two way traffic volume across the bridge in vehicles per day C the two way capacity of the bridge during normal i e non project periods in vehicles per day C the two way capacity of the bridge during the project period for the treatment in vehicles per day accounting for typical lane closures throughout the project and assuming the typical pattern of peak hour and off peak demand B an exponent with a default value of four D the total deck area in square feet S the index of deck area distress at the time of the treatment P the productivity of the treatment in square feet per day M a fixed time as for mobilization in days This formula estimates incremental user costs due to congestion that will be incurred by the traffic stream fo
27. Compatible Treatment Alternatives This chapter will provide a range of treatment alternatives from which the selection can be made Prior to selecting all of the treatment alternatives in this chapter the user will consult the tables provided screening out those alternatives which are not compatible with the concrete because of their technical disadvantages 2 7 Chapter 9 Cost Items Associated with Treatment Agency Costs Costs associated with various treatments should be known so that life cycle cost analysis can be conducted Cost can vary significantly from one area to another depending on many factors The user generally has most reliable information regarding cost of a certain treatment in a given jurisdiction However before the user arrives at any cost for a treatment the standard cost items associated with that treatment must be identified Chapter 9 will provide standard highway agency cost items associated with each treatment covered in the handbook 2 8 Chapter 10 Cost Items Associated with Treatment User Costs Two types of user costs are considered in this chapter 1 prior to treatment costs decks only and 2 during treatment costs Costs in the period prior to the treatment are a function of the condition of the bridge deck and its effect on traffic flow A badly spalled deck would impede traffic flow causing speed reduction and congestion and resulting in increased travel time and cost Costs during the treatment a
28. Concrete Bridge Protection Repair and Rehabilitation Relative to Reinforcement Corrosion A Methods Application Manual Report no SHRP S 360 Strategic Highway Research Program National Research Council Washington DC 1993 Bennett J J B Bushman J J Bartholomew K C Clear R N Kamp and W J Swait Cathodic Protection of Reinforced Concrete Bridge Elements A Manual of Practice Report no SHRP S 372 Strategic Highway Research Program National Research Council Washington DC 1993 Beaton J L and R F Stratfull Environmental Influence of Corrosion of Reinforcing Steel in Concrete Substructures Highway Research Record 14 HRB National Research Council Washington DC 1963 pp 60 78 Spellman D L and R F Stratfull Laboratory Corrosion Test of Steel in Concrete Interim report no M amp R 635116 3 California Division of Highways 1968 Recording and Coding Guide for the Structure Inventory and Appraisal of the Nation s Bridges Federal Highway Administration U S Department of Transportation 1979 Construction Costs and Safety Impacts of Work Zone Traffic Control Strategies Report no FHW A RD 89 209 Federal Highway Administration U S Department of Transportation 1989 A Manual on User Benefit Analysis of Highway and Bus Transit Improvements American Association of State Highway and Transportation Officials Washington DC 1977 289 d EIU er S S E EIRE Ca Concrete and Structu
29. EE FDm a m Y r a rs Item Default s Example _ Fixed cost 0 10 000 time required days 0 5 Deck cost sq ft 0 00 6 00 productivity sq ft day 0 00 400 00 CL cost sq ft 0 00 0 00 productivity sq ft day 0 00 0 00 DL cost sq ft 0 00 0 00 productivity sq ft day 0 00 0 00 SP cost sq ft 0 00 35 00 productivity sq ft day 0 00 135 00 Maintenance cost year 0 0 274 Table A 4 Treatments Estimated Life and Repair After Treatment Data Item Default Example Effect on chloride N Y CL following treatment of 0 0 0 0 area Effect on delamination DL following treatment of 0 0 0 0 area Effect on spalls SP following treatment of 0 0 0 0 area Nominal life years 0 0 10 0 Corrosion model 1 3 K 0 3333 0 0000 Life with no corrosion years 0 0 Table A 5 Treatments Effect on Traffic M SS SY RS SS SS aap akana Item Default BEEN Example O Traffic Impact Congestion Congestion Unit user cost min per veh 0 0000 0 25 Congestion formula coefficient 0 1500 0 1500 Congestion formula exponent 4 0000 4 0000 Capacity during project veh day 100 000 100 000 Detour time min veh 0 00000 276 Table A 6 Corrosion Input Data Item Default Example Analysis base year 1994 1994 Maximum tolerable distress 45 0 45 0 Previous repair N N WIC deck concrete 0 50 0 45 Number of cover data 1 10 Protective system N N Present condition Y Yt Example data for illustrativ
30. If you select OVERLAY CORRODE will recognize that the OVERLAY file associated with CONCRETE is different from the OVERLAY file associated with bridge BRIDGE You may therefore edit these two files independently of each other from this point on Once a file is copied you may edit it as you would any other treatment file Refer to the previous section on editing existing treatment files This allowance extends even to the name of the file If you edit the name of a treatment file plus any other data therein it is as though a new file of the same name were defined CORRODE may provide you an informational message on this point saying that a file originally defined for the former bridge has been reassigned to the latter bridge This is for your information only and has no effect on the files in question As an illustration consider the example above Assume that you copy the BRIDGE OVERLAY file into a new file CONCRETE OVERLAY where the slash denotes a bridge file treatment file combination You now edit the CONCRETE OVERLAY file since CONCRETE remains the selected bridge but in so doing you also change its name to OVLY 1 When you are finished CORRODE will associate two treatment files with bridge file CONCRETE OVERLAY which remains the same as when it was copied and OVLY 1 which reflects your editing changes 4 5 Contents of the Treatment File The contents of a treatment file are the same regardless of whether you ar
31. SUIT 9 8J UOISOIIOO SU Iopun Bory SI 9 VUI 09 UOISOIIOO 10 2Arje nurmn 9 UL SNSAIA HVY UOISOLIO ANSIA o 1 SIE9 y Y C OI 43 bs ywu jey uotso L10 39 2 the time required for additional cumulative corrosion equal to the area under corrosion rate line from t to tm 60 7 milli amperes per square foot years 653 4 milli amperes per square meter years in the example above to take place Technical Goal 3 discusses Item 1 above Determining Item 2 requires data concerning the effect of the treatment on the corrosion rate Figure 8 depicts four different possible effects of a treatment on the rate of corrosion In Case 1 the corrosion rate continues to increase at the same rate as before the treatment In Case 2 the corrosion rate is frozen at the value when treatment was performed In Case 3 the corrosion rate practically drops to 0 as soon as the treatment was performed and in Case 4 the corrosion rate decreases slowly with time Each candidate treatment will be assigned a default number based on the trend of rate of corrosion line i e slope of the line after the treatment and the system user will be able to adjust the numbers Once the shape of the after treatment corrosion rate line is defined it is a relatively simple mathematical calculation to determine the number of years required to equalize the area under the after treatment line with the area under the before treatment li
32. area of 4 000 square feet Han activity has a productivity of 200 square feet per day the total time estimated for this activity will be 20 days If the cost is 25 00 per square foot the total cost estimated will be 100 000 CL cost and productivity components of cost and productivity related to work to address only those areas of the deck that are chloride contaminated The unit cost entered here is in dollars per square foot of chloride contaminated deck area the productivity is expressed in terms of square feet per day applied only to the chloride contaminated area CORRODE computes the estimated area of chloride contamination over time in the life cycle cost analysis Chapter 5 DL cost and productivity components of cost and productivity related to work to address only those areas of the deck that are delaminated excluding spalls The unit cost entered here is in dollars per square foot of delaminated deck area the productivity is expressed in terms of square feet per day applied only to the delaminated area CORRODE computes the estimated area of delamination over time in the life cycle cost analysis Chapter 5 SP cost and productivity components of cost and productivity related to work to address only those areas of the deck that are spalled The unit cost entered here is in dollars per square foot of spalled deck area the productivity is expressed in terms of square feet per day applied only to the spalled area CORRODE c
33. by Weyers et al and by Bennett et al The user may of course change treatment procedures outlined here to suit agency policies and practices 9 1 Cost Items Associated with Applying Deck Treatments Concrete Patches Cost items in this category are as follows e Removing contaminated and or deteriorated concrete e Patching with concrete and curing e Traffic control when bridge is partially open to traffic 149 Cost items in this category should be expressed in terms of dollars per cubic yard of patches or dollars per square foot of patches if the depth of the patch is taken into consideration Corrosion Inhibitor Application Cost items in this category are as follows e Applying corrosion inhibitor When there is not an existing overlay spray the inhibitor to soak into the concrete When there is an existing overlay this treatment may not be considered e Traffic control when the bridge is partially open to traffic Cost items in this category should be expressed in terms of dollars per square foot of deck area Concrete Overlays Cost items in this category are as follows e Surface preparation When there is not an existing overlay scarify the concrete surface sand or shotblasting for polymer concrete When there is an existing overlay remove the existing overlay e Placing and curing concrete e Traffic control when the bridge is partially open to traffic Cost items in this category shou
34. chloride distribution and the estimated rebar level chloride at the 90 percent confidence limit When you are finished entering the data press F10 e Locked in the aggregate if the information and data available point to chloride bearing aggregates in the concrete that contribute to corrosion enter Y otherwise enter N If you have entered Y CORRODE prompts you for input in the next item of the form benign chloride e Benign chloride if CORRODE makes this field available enter the estimated percentage of benign chloride by weight of concrete Benign chloride refers to chloride locked in the aggregate that will not contribute to corrosion If previous experience with the aggregate indicates benign chloride enter the percentage here to modify the threshold chloride value used in the corrosion analysis When you have completed data entry to this input form press F10 to save these changes or Escape to ignore them Analysis Prior to Start of Deterioration CORRODES s analysis of the current bridge condition may indicate that corrosion related distress may not yet have begun CORRODE must still estimate the slope of the deterioration versus time curve that will occur after corrosion becomes active in the future At this future time chloride will be present in excess at the level of reinforcing steel the corrosion and deterioration rates will be dictated by many factors including the steel concentration oxygen availability and resist
35. critical surface chloride value may be obtained using the procedure outlined in Appendix F If the answer is NO we proceed to the Present Information Module If the answer is YES The following list of possible protective systems is provided and the user is requested to designate those which are included and to define the years of additional service i e years of additional time to deterioration which result from each protective system Note that these years of service are in addition to that provided by the concrete itself which is affected by water cement ratio and cover depth Epoxy Coated Reinforcing Steel Latex Modified Concrete overlay Concrete Overlay including low slump dense concrete Silica Fume Concrete Full Depth Silica Fume Concrete Overlay Waterproof Membrane with Asphalt Concrete Overlay Penetrating Sealer Oy DE 20 Table 1 Comparison of Evaluation Schemes SHRP Condition Evaluation Manual 1 Concrete Permeability T Concrete permeability and resistivity Determining the relative permeability of concrete AASHTO T277 and KCC INC Resistivity in the field as in appendix G of Volume 8 surface AASHTO T277 is required for permeability when airflow representative water cement ratio of concrete is needed Reasons Lack of adequate data relating water cement ratio and permeability by surface airflow States are more familiar with AASHTO T277 test method which has a
36. data input form move between fields using up down arrows move within a field from character to character using the right left arrows e Selecting options When CORRODE provides a list of options and asks you to select one move the cursor with the up down arrow keys to your choice and make your selection with the Enter key e Entering data When CORRODE asks you to enter data whether alphanumeric as for the name of a file or numeric as for bridge dimensions or corrosion data it will provide a field for entry Use the standard keyboard to enter or edit data and the left right arrow keys to move about in the field The backspace delete and insert type over keys should work normally If a default entry or your prior entry is already 213 provided in the field you may either accept this entry by pressing Enter or you may clear the field by pressing F6 and then enter new data After data have been entered press Enter to complete your entry Available fields most fields will appear in one color cyan on color monitors indicating that you may input or edit data therein Fields of a contrasting color e g red characters on black background indicate that these fields are unavailable for input or editing CORRODE controls the availability of fields to indicate valid options Often it determines what fields are valid in response to information you have already provided Invalid entries If you make an invalid entry CORROD
37. decision to treat a concrete bridge component To convert to metric units in this example one square foot is 0 929 square meters one inch is 2 54 centimeters one pound per cubic yard is 0 59 kilograms per cubic meter one dollar per square foot is 10 76 dollars per square meter and one foot is 0 3 meters 14 1 General Description of the Example The concrete bridge component to be examined is a bridge deck with an area of 10 000 square feet The concrete bridge deck was placed in 1978 and it contains black reinforcing steel The concrete is a conventional concrete with a specified water cement ratio of 0 45 assume actual water cement ratio 0 45 0 03 0 48 unless field information exists and a specified bar cover depth of 1 5 inches The concrete has not received any treatment since 1978 The average two way daily traffic volume across the bridge is 15 000 vehicles The concrete deck has been exposed to de icing salt during its service but background chlorides do not exist in the concrete Reinforcing steel corrosion induced deterioration has been present and is a concern The expected remaining service life of the structure due to bridge functional features is 50 years i e unlimited remaining service life see Chapter 3 The highway agency that owns the bridge would like to determine when the bridge should be treated against chloride induced corrosion and what type of treatment should be applied 191 14 2 Systematic P
38. item of information the average detour time per vehicle in minutes This value should reflect the incremental increase in travel time caused by the detour averaged throughout the day to account for variations in flow and congestion Adjustment Factors Adjustment factors were discussed in the early stages of CORRODE system design as a means to perform sensitivity analyses automatically As of now they are not implemented 245 5 Analyses 5 1 Overview CORRODE includes two basic capabilities to help you analyze bridge deck condition and treatments A corrosion analysis which considers inspection data and observations of the bridge deck concrete estimates key corrosion related parameters and the current condition in terms of a distress index and uses a deterioration model to predict the change in distress index over time A life cycle cost analysis which considers the deck deterioration model estimated above together with predictions of agency costs and bridge user costs associated with a treatment to estimate the life cycle costs of that treatment These life cycle cost estimates yield the optimal time of treatment performance when life cycle costs are at their minimum These two analyses are handled as distinct steps in CORRODE as illustrated in Figure 4 Since a life cycle cost analysis requires the results of a corrosion analysis the corrosion analysis must precede any life cycle cost run that refers to it Beyond th
39. keeps track of which corrosion files are assigned to what bridges The name of the currently selected corrosion file appears in the information bar at the bottom of the screen to the right of the selected bridge file Corrosion Input Data Once file names are chosen CORRODE displays the input data in the start with file You may edit these data and the results will be stored in the results file The input data are as follows e Analysis base year the calendar year for which the corrosion analysis results will pertain Generally this would be the current year e Maximum distress enter the maximum level of distress that can occur before some remedial work absolutely must be done This input referred to as S in Part I of this document is intended to provide an absolute upper bound to the level of distress that will be accepted in the analysis performed by CORRODE It is not indicative of a standard or of your department s practice nor is it the level at which you think a treatment 249 should be done Given its intended meaning a deck will likely be repaired before this threshold is reached CORRODE will restrict the solution according to this maximum i e it will not allow the deck condition to worsen beyond this threshold and it will force a treatment at that time e Previous rehabilitation enter Y if the deck has been previously rehabilitated N if it has not If your response is yes a separate input form will be displaye
40. life cycle cost and 2 when concrete is treated and protected positively the most cost effective strategy is logically the one that gets the maximum possible use out of the treatment All costs associated with each strategy including costs of repeated cycles of treatment within the planning horizon agency costs and user costs and salvage value of the last cycle of treatment are then discounted and totaled for comparison with the other strategies At the end of this economic analysis the user will be able to determine the optimum strategy time of treatment for a compatible treatment Also the user will be able to prioritize the various compatible treatments based on their life cycle costs Detailed procedures are described in the following sections 13 1 Life Cycle Cost of a Selected Treatment and Strategy For a selected compatible treatment and a selected strategy the life cycle cost can be estimated by tabulating the strategy in the worksheet shown in Figure 13 1 Figures 13 2 13 3 and 13 4 are examples of tabulated strategies of treat at t treat at tm and treat between t and t respectively To estimate each strategy s life cycle cost use the following step by step procedure to tabulate the three strategies for a selected compatible treatment in Figure 13 1 Step 1 Planning Horizon Columns 1 and 2 correspond to the 20 year planning horizon Fill out Column 1 by starting with the present date in the first row 1992
41. obtained year the member was constructed How many surface chloride values are available Input surface chloride values taken from 0 25 in 0 6cm to 0 75 in 1 9cm depth Calculate the average and standard deviation of surface chloride values 90th percentile surface chloride average t 1 282 standard deviation Calculation One Submodule S 1 9 Fit the two points to the distress equation 65 66 Flowchart 7 Calculation One Submodule This module calculates the time to first deterioration t using the following formula 1 t 2695d 2097 z Lr P Where t time to first signs of corrosion induced distress years d depth of bar cover inches Z surface chloride concentration percent by weight of concrete t age at which Z was measured years and P concrete water cement ratio Flowchart 8 Pre Deterioration Submodule Year in which surface chloride samples were obtained Year to this surface chloride buildup year surface chloride samples obtained year member constructed How many surface chloride values are available create an array of this size to store all values Input surface chloride values 0 25 in 0 6cm to 0 75 in 1 9cm Calculate the average and standard deviation of surface chloride values Calculate 90th percentile surface chloride average 1 282 standard deviation Is surface chloride lt 0 10 yes Input mean annual snowfall in inches
42. point needed to estimate the deck deterioration function Surface Chloride Surface chloride levels are part of CORRODE s estimation of future corrosion and deterioration Data to be input are as follows Year of surface chloride survey enter the calendar year in which this survey was performed e Number of surface chloride values enter the number of surface chloride values obtained in the field After you enter this number and press Enter CORRODE displays an input sheet in which you enter each surface chloride data point in percent by weight of concrete CORRODE will use this information to compute the mean and standard deviation of the surface chloride distribution and the estimated value at the 90 percent confidence limit When you have finished entering the surface chloride data press F10 e Mean annual snowfall enter the mean annual snowfall in inches This measure is used as a surrogate for salt applications on the bridge deck It is applied only if CORRODE determines that the current surface chloride values are extremely low average less than 0 1 percent by weight of concrete because of lack of exposure age and that the estimate of the future time to deterioration t may therefore be incorrect In that case the annual snowfall will be used with other factors to adjust the estimated value of time to deterioration Exposed to a marine environment indicate Y or N whether the deck is exposed to a marine environ
43. ratio of DELAM to SPALL as discussed in the assumptions SPALL DELAM N DELAM does not include SPALL Equation 11 3 161 12 Prediction of Performance Treated Concrete The methodology employs life cycle cost analysis to determine the cost effectiveness of a proposed treatment Therefore the service life of the treated concrete also needs to be predicted The aim of this chapter is to predict the effective service life expected of the treated concrete As defined in this chapter at the end of the effective service life of the treated concrete the concrete condition index is the maximum tolerable S Use the following procedures to predict the effective service life of the treated concrete Apply the same effective service life to the next cycles of treatment It should be noted that in order to achieve the effective service life predicted for the treated concrete in this chapter the treatment may be repeated depending on the durability of the treatment itself This may include reapplying sealers coatings removing and replacing overlays and renewing cathodic protection systems The user should determine the service life expected of the treatment itself on the basis of environmental factors SHRP research by Weyers et al may be consulted for this purpose 12 1 Case 1 Concrete not Repaired Rehabilitated and or Protected Previously Case 1 applies to all concretes which will be repaired rehabilitated and or protected for the
44. reasons for the differences Returning to the questions asked in this module Question 1 What is the water cement ratio of the concrete surrounding the reinforcing steel An answer in the range of 0 2 to 0 7 is required The ratio may be obtained from project records or by other means This information will be used to calculate t concrete age at the time of first sign of deterioration on members which have not been previously repaired if t is not otherwise known Question 2 Is data on the actual reinforcing steel cover available If the answer is NO the user is asked to input the design cover in inches and the 10th percentile cover value is calculated as the design cover minus 0 48 inches 1 2 centimeters a standard deviation of 0 38 inches 0 97 centimeters is assumed Of course the result must be greater than 0 If the answer is YES The user is asked to input the cover data and the average standard deviation and 10th percentile cover value average cover 1 282 standard deviation is calculated The recommended minimum number of cover measurements is 40 per member or per 5 000 square feet 465 square meters whichever results in the larger number of measurements Question 3 Was the concrete constructed with a corrosion protective system listed below or was one added before the surface level chloride exceeded the critical value UYI VY S3 Y CO MIN CIA A SSS ae which would later diffuse and cause bar corrosion the
45. reductions congestion and resulting increase in travel time and cost Use the following equation or Figure 10 3 to find user costs due to worsening deck condition for a given year U K S S 365 q Equation 10 3 where U user costs due to worsening deck condition dollars per year K a calibrating constant dollars per vehicle K a t K See During Treatment Costs for definitions of K and t Parameter a is the percentage of free flow travel time t representing the increment in travel time when S S S concrete condition index for the year considered Chapter 6 maximum tolerable condition index Chapter 5 q average two way daily traffic volume across the bridge vehicles per day 156 Figure 10 1 Nomogram for User Costs During Treatment PAA TIT SNI LLL NW Op 1d LX 157 wn e orqoA uty 3807 19s P9ZI ERLION spuesnom 3 sapnu un JoAu1 ur juomoJoug 0 001 OST 00 SO O 00 scOO 00 SscO0O COO STOO jusurjeoag ZUMA s3so Jos 10J MVAZOMION panurmuo TOT ng 158 0 3 SOMU TL fader uy juoura oug I9 b uorongsuo Suunq Qrsde 0 der Apieq ode1oay Jo one T00 c00 0 0 t00 I OT 6 0 8 0 L0 9 0 0 v0 0 c0 To E 1 2 a n 2 oSpi1g SSOIDY oup PAVLL ur juaurmsIouJ oururiojoqq 0 WIBIZOWION Z OT 93nZiq 159 160 Figure 10 3 Nomogram to Determine User Costs Prior to Treatment e A o o
46. spalled The distress index is defined on a scale of 0 to 100 with an increasing index value denoting increasing distress in the deck Although the maximum index value is mathematically 100 it is believed that a practical limit exists beyond which a functioning deck should not go without rehabilitation You input a value for this practical maximum level of distress 259 The corrosion analysis seeks the time variation in the distress index i e a deterioration function expressed as a logistic or S shaped curve To estimate this curve the corrosion analysis determines the condition of the deck at key points in its history or future depending on whether or not the corrosion mechanisms have already begun These key points are t the time to the start of deterioration t the present time and t the time to reach the maximum level To estimate the deterioration function the corrosion analysis requires that only two of these three points be determined It is assumed that at the time to the start of deterioration t the condition index is defined to have a value of 1 9 This value corresponds to the assumption of 10 percent chloride contamination 0 percent delamination and 0 percent spalling Thus the corrosion analysis needs only to determine t to obtain one of the two required points It computes t using a modified Stratfull formula For the second point the corrosion analysis uses one of the following two approaches depending on w
47. surveys are used only to identify the most anodic areas to locate points for corrosion rate measurements when bar level chloride is greater than chloride threshold 0 035 percent Survey done at all times 21 8 Surface Protective Coating 9 Concrete with Corrosion Inhibitor Admixture 10 Cathodic Protection 11 Other Thus for each protective system designated the question is asked How many years will the first signs of deterioration be delayed by the designated protective system An answer is required but the effect of the conventional concrete as defined by its water cement ratio and the reinforcing steel cover must not be included in the answer The answer will be added to t from the Pre Deterioration Submodule if that module is used When a corrosion inhibitor admixture is used as the protective system an additional question is asked How much inhibitor is used in the concrete The Present Module will use the answer to adjust the chloride threshold used in determining the present condition index S e g 0 035 percent of concrete weight For concrete overlays low slump dense latex modified and silica fume the water cement ratio for input into the t formula must be adjusted to reflect the average water cement ratio of the concrete cover i e part may be overlay and part may be base concrete To accomplish this the following questions are asked What is the thickness of the overlay What is the ov
48. that are included as protective systems in CORRODE e Present Condition indicate Y or N whether the data on the deck are from a survey of the condition with respect to corrosion If your response is Y a separate input form will be displayed as described in a section below Three specialized input forms are mentioned above dealing with previous deck repair protective systems and present condition survey data respectively These additional data input forms are shown schematically in Figure 5 Details on these are presented in the sections below Note Several data collection and testing procedures are alluded to in the following sections These procedures are summarized in Table 3 and described in Appendix B 250 Figure 5 Additional Forms for Input of Corrosion Data Corrosion Input Data Form Figure 4 Previous Repair Year of Repaired Spalled Delaminated Chloride Areas Remaining Following the Previous repaired Protective Systems Indicate Which Protective Systems Have Been Installed Epoxy Coated Rebar Latex Modified Concrete Overlay etc Survey of Present Condition Year Surveyed Area Spalled Delaminated Area Rebar Chloride Values Benign Chloride Remaining Corrosion Data See Figure 6 251 Table 3 Number of Tests and Samples Procedure Methodology Visual Examination Use 5 foot grid on deck 2 5 foot grid on sub and superstr
49. the Strategic Highway Research Program SHRP SHRP is a unit of the National Research Council that was authorized by Section 128 of the Surface Transportation and Uniform Relocation Assistance Act of 1987 This report is a product of the research conducted under SHRP Project C104 by Wilbur Smith Associates Ronald L Purvis of Wilbur Smith Associates was the principal Investigator for the research Kenneth C Clear Inc and Cambridge Systematics Inc were subcontractors to the research project The methodology to predict the performance of concrete is primarily based on the concepts developed by Kenneth C Clear and Siva Venugopalan of Kenneth C Clear Inc Michael J Markow of Cambridge Systematics Inc developed the basic equation of performance for concrete as well as the concepts to determine the user s costs The authors wish to thank those who provided many useful comments and suggestions during the course of the work reported in this document They extend special thanks to the members of the Expert Task Group for SHRP Project C104 members of the SHRP Concrete and Structures Advisory Committee and Department of Transportation staff in the states of Minnesota New York California Pennsylvania and Washington lil Foreword This report consists of three parts Part One discusses the development of a systematic methodology to determine the most cost effective treatment and its timing for specific concrete bridge components th
50. the bridge descriptions are contained in bridge files Procedures to create and edit treatment files are likewise similar to those for bridge files The organization of treatment input options is illustrated in Figure 3 The following sections describe the options available in the TREATMENT submenu and the data contained in each treatment file The TREATMENT menu provides three options e Editing a previously defined treatment file Creating a new treatment file 231 Table 1 Selection of Compatible Deck Treatment Alternatives Technical Conc AC Seal Cathod Reason Disadvantage Over Memb Coat Protect Additional dead load Not Not Not Overlays add to dead load critical Good Good Good Active cracks in conc Not Not Active cracks reflect through Good Good concrete Existing overlay on Not Not Removal of old system results deck Good Good in rough surface Concrete surface Not Rough concrete surface scaled Good Existing slotted Not Scarifying concrete damages cathod protect Good anodes Existing polymer Not Good Insulated bars injection repair in concrete Electricity not Not Cathodic protection needs available Good electricity Skid resistance Not Skid resistance may decrease critical Good Steep grades and or Not Concrete may flow after strike crossfalls Good off Sharp skew and or Not Difficult to pave with concrete curvature Good finishing machines 1 When cathodic protection is used with an overlay 2 Unless
51. the deck The chapter recommends a default value for the maximum tolerable condition index 2 4 Chapter 6 Prediction of Performance In this chapter a systematic procedure is presented for predicting the condition index of concrete at any given time in the future This is done through a performance equation that relates fh condition index to the age of concrete There are two parameters in the equation which are systematically determined from the site specific data Nomograms have been prepared as an alternative to hand calculations to determine the two parameters of the performance equation 2 5 Chapter 7 Evaluation of Performance Chapter 6 established a performance equation which relates the concrete condition to the age of concrete Chapter 7 will assist the user to understand the rate of deterioration of the concrete by illustrating the equation graphically On the basis of two parameters of the performance equation obtained in Chapter 6 the user will select the performance curve from a family of curves From the performance curve the user will define the period of time between present time and time corresponding to the maximum tolerable condition index determined 98 from Chapter 5 This is the treatment consideration period The rest of the handbook Is used to determine the timing of the treatment within the treatment consideration period as well as the type of the treatment for maximum cost effectiveness 2 6 Chapter 8
52. the handbook are devised on the basis of the concepts developed in Part I of this document The results of SHRP research by Cady and Gannon were used to make a reliable determination of the condition of the concrete Also the SHRP research by Weyers et al was used to develop concepts for determining concrete service life Both agency costs and user costs have been taken into consideration in conducting life cycle analysis 1 3 Scope The methodology in its present form only applies when the predominant concrete deterioration is associated with chloride induced corrosion of the reinforcing steel 95 The procedures outlined in the handbook are primarily devised for exposed concretes but they also apply to covered concretes Where a procedure does not apply to covered concretes adjustments have been made for covered concretes and explained The procedures in the handbook determine the life cycle cost when the concrete is treated at the present or in the future Those procedures however can be employed to determine the life cycle cost if the concrete was treated in the past Of course the latter life cycle cost information cannot be used for planning a treatment However it could be used to compare strategies The methodology is designed to be flexible and can be tailored to suit the needs of the individual highway agencies The user has the option of deleting those aspects of the methodology that are irrelevant to a specific case 96
53. the selected bridge always appears in the information bar at the bottom of the screen following the Bridge tag If this name identifies the bridge file you wish to work with the bridge is already selected and you may proceed If this name is different from the file you wish to work with or if you are not sure and would like to check the names of the bridge files already defined then choose the SELECT BRIDGE option e CORRODE will display the names of currently defined bridges if any Use the up down cursor keys to scroll through the list until you find the bridge file name you wish to select 225 Figure 2 Bridge Menu Options Bridges New Bridge Select Bridge Edit Bridge Bridge Description File Name Comment Year Constructed Deck Area e Traffic Capacity User Cost Information 226 Press F10 to complete the selection The name of the selected bridge file will appear in the information bar at the bottom of the screen 3 33 Editing an Existing Bridge File You may edit an existing bridge file at any time to update information complete a description you began earlier or correct previous errors However the CORRODE system lets you edit only the currently selected bridge file If the file you wish to edit is not currently selected please refer to the preceding section on selecting bridges before you proceed with editing Once you have selected the correct bridge file choose
54. the user will see only a short series of questions and then the findings A sample computer run is demonstrated for Technical Goal One Condition Index Versus Time in Appendix B This computer run is not related to the CORRODE system described in Part III of this document 12 2 Technical Goal One Condition Index Versus Time 2 1 Condition Index The first step is to quantify the concrete condition Current research on this and other SHRP research projects suggests that three quantities are indicators of current concrete condition as affected by corrosion 1 Percent of bar level concrete samples with chloride content higher than the corrosion threshold value CL 2 Percent of concrete area that is delaminated DELAM not including spalls 3 Percent of concrete area that is spalled SPALL Of these when considering treatment options at a given time spalling is the most important factor delamination is second in importance and chloride contamination at the level of reinforcing steel is the third most important For the purposes of this project the relative importance of each of these three factors as an indicator of the need of treatment is expressed by assigning the following weights Spalling is three times more important than delamination while delamination is 2 5 times more important than bar level chloride contamination The condition index S may then be quantified at the time of condition survey and on the basi
55. traffic flow causing speed reductions congestion and an increase in travel costs and vehicle operating costs Use Equation 4 3 to find user costs due to worsening deck condition for a given year U K S S 365 qo Eq 4 3 where U user costs due to worsening deck condition dollars per year K a calibrating constant dollars per vehicle K a t K See During Treatment Costs above for definitions of K and t Parameter a is the percentage of free flow travel time t across the bridge representing the increment in travel time when S Sa concrete condition index for the year considered eo It S maximum tolerable condition index see Section 5 2 qo average two way daily traffic volume across the bridge vehicles per day n typically 4 4 3 Maximum Possible Service Life of a Treatment The maximum possible service life of a treatment e g sealer overlay etc depends on the durability of the treatment itself and is independent of the corrosion induced deterioration of the underlying reinforced concrete The bridge environment also affects the maximum possible service life of a treatment The level of traffic for decks and the weather condition e g freeze thaw wet dry have a definite role in the durability of various treatments The user should provide the maximum possible service life of a 33 selected treatment based on the factors discussed The user with no previous experience wit
56. treatment for each consecutive year in the planning horizon Chapter 10 Step 5 User Costs During Treatment Column 8 is for user costs during the treatment Chapter 10 Step 6 Discount Factor Column 9 is for the discount factor Using the equation given below find the discount factor for each consecutive year in the planning horizon alternatively use Figure 13 5 DF 1 1 ED Equation 13 2 where DF discount factor EI effective interest rate interest rate minus inflation rate n number of each consecutive year in the planning horizon Fill out the boxes of Column 9 with the discount factors Step 7 Present Worth Column 10 gives the sum of the costs in each consecutive year in current dollars present worth Multiply the sum of all costs in each consecutive year by the corresponding discount factor and fill out the boxes of Column 10 with the products 188 Figure 13 5 Discount Factors I a m m a uw o9 om a oem oom C owe us w cem we i aa pos NENNEN Len _ NENNEN o n o o om ou os om om s ow om omo x u om m omo Oo s om om o omo ENTE Doom ENT EN 0 700 e a Em 1 EI Effective Interest Rate Interest rate Inflation rate 189 Step 8 Total Present Worth Add up all costs in Column 10 This is the total present worth as shown in the bottom of Figu
57. two considerations by allowing you to copy a treatment file defined for one bridge to a new file to be applied to a different bridge You may then modify whatever information if any needs to be changed to reflect the application of this treatment to the new bridge In this way the integrity of each bridge treatment combination is maintained but you have the flexibility to use previously defined treatments to the greatest advantage possible without having to input the treatment descriptions anew for each bridge Select the COPY TREATMENT option in the submenu CORRODE will provide you with a set of choices in sequence as follows e First specify the bridge from which you would like to copy the treatment You might for example select a bridge whose location size structural characteristics traffic etc match most closely the bridge in question Or you might select a bridge for which the estimates of treatment costs production rates etc are in your opinion the most current Perhaps there is only one other bridge for which this treatment has been defined previously There is no requirement that you copy any previously defined treatment you may elect instead to define a new treatment file from scratch using the NEW TREATMENT option rather than COPY TREATMENT The whole purpose of COPY TREATMENT is to make a time saving approach available to you in defining your set of treatments throughout the bridge network Next CORRODE wil
58. user costs Step 5 User Cost During Treatment Fill out the appropriate boxes of Column 8 with the user costs during the treatment See G above for U Strategy Treat at t To find user costs during the treatment Concrete Removal Patching at 200 square feet per day 3 days Overlay Placing Curing at 2 000 square feet per day 5 days Total time t 8 days U 40 000 Strategy Treat at t To find user costs during the treatment Concrete Removal Patching at 200 square feet per day 27 days Overlay Placing Curing at 2 000 square feet per day 5 days Total time t 32 days U 160 000 Use the same user cost when treatment is repeated at Sn 205 Strategy Treat between t and t To find user costs during the treatment Concrete Removal Patching at 200 square feet per day 9 days Overlay Placing Curing at 2 000 square feet per day 5 days Total time t 14 days Ui 70 000 Use 160 000 as user cost during treatment when treatment is repeated at S Step 6 Discount Factor All Strategies Find the discount factor for each consecutive year in the consideration period assuming an interest rate of 7 percent and an inflation rate of 3 percent or an effective interest rate of 7 3 4 percent Equation 13 2 or Figure 13 5 Fill out the boxes in Column 9 with the discount factors Step 7 Present Worth All Strategies Multiply the sum of all costs in each consecutive year by the corresponding disco
59. 0 00S oos EO VI SC AVANSIsal IH OLOTO t6L cs 09 TS SC 82 0 00S 0007 0 tI SI C vt eC VI St O 008E 0007 0 Vi 09 It 08 TI Sv 0 008E 00LL 0 rI SC AWANSISAI aeIOPOW C981 O L9 EL EE L I er 0 008 0 8 0 VI SI Py Jod 0 SUIT IO 949 PNS o nuoo19q qot 19A02 syuoururoo SJUE SUO 0 SUIT 8 V sr puoo ae as squio no onel O M Lda SOTITTIQUOULIOg JUA JO 21919u0 10J cp Jo x opul uonipuoO 0 S1e3A JO o durexq s1eo ody 9 npouirqngs oA uont no e 86 J83AX WIL s ntTIiqe urq JUDAIC JO 2121900 107 9AInO uonrpuo o npouiqns OAT Uone An ns SOY MOT OI 07 0t Ot 0S 09 0L 08 06 001 ipuo x pul uon 87 Appendix F Criteria for Preventive Maintenance 89 Criteria for Preventive Maintenance Problem Let us consider a structure for example a bridge deck constructed 5 years ago with 0 15 percent surface chloride measured at between 0 25 and 0 75 inches 0 6 to 1 9 centimeters from the surface The bar level chloride is below the threshold at present Is it feasible to apply a sealer membrane or overlay to prevent corrosion If so how many times can we apply this kind of protective system as a preventive maintenance before the 0 15 percent surface chloride causes the bar level chlorides to exceed the threshold Procedure to Determine the Applicability of a Protective System with 100 Effectiveness Examp
60. 16 percent and spalling is 4 percent Thus the condition index at present is CL 2 5 DELAM 7 5 SPALL 8 5 90 2 5 16 7 5 4 8 5 18 8 Sp S S Consistent with the assumption for the age of concrete at the repair the age of concrete at the present t is 1992 1985 7 years A plot of these results using the condition index versus concrete age equation is presented in Figure 5 The condition index see Equation 2 2 used for Figure 5 is S 100 1 10 36 exp 0 125 years 27 OF J 3 WIL St 0t C 0C SI OI d 881 S NINES pouredoy A snowsg w 10 oAJ1n xopug uonipuo ojdureg S dns 00 0 00 0 00 0t 00 0 00 09 00 0L 00 08 00 06 00 00I x pul uonipuo 28 3 Technical Goal Two Decomposing Condition Index Condition index or distress index S needs to be decomposed into its component parts i e percent chloride contamination percent delamination and percent spalling at various points in the future for the purpose of estimating treatment cost This can best be accomplished by applying a series of rules or ratios as listed below 1 For all deck concrete except those with 1 inch 2 54 centimeters or thicker concrete overlays DELAM is 4 times SPALL For all deck concrete with 1 inch 2 54 centimeters or thicker bonded concrete overlays DELAM is 8 times SPALL 2 For all non deck concrete except those with 1 inch 2
61. 355 895 207 Figure 14 1 Worked Example of Tabulated Treatment Strategy Treat at t Date Cond Treatment Agency Agency User Index Type Cost Cost Cost S Initial Maint Prior to Treat Treat Patch 77 000 40 000 117 000 LSDC 0 790 0 759 0 730 0 702 0 675 710 0 649 898 1 116 23333333331111333341 I 9 ams ETE 0577 EL 0888 17 me 0 534 Ea EUN 0 474 Total Present Worth 136 074 Salvage Value 15 845 Life Cycle Cost 120 229 208 Figure 14 2 Worked Example of Tabulated Treatment Strategy Treat at t Cond Treatment Index Type 7 1 3 T e 2 gt 0 Patch 241 500 160 000 0 702 281 853 LSDC S J e t2 B oo put b oo 15 174 20 352 Total Present Worth 526 961 Salvage Value 171 066 Life Cycle Cost 355 895 209 Figure 14 3 Worked Example of Tabulated Treatment Strategy Treat between t and tn Date Year Cond Treatment Agency Agency User Index Type Cost Cost Cost S Initial Maint Prior to Treat oo a e Patch LSDC 1997 17 9 10 3 7 Lo asa 1 108 1 710 2 531 17 2 e 6 o6 210 During Treat 70 000 082 x ono 0 730 808 0 702 1 200 0 675 1 708 0 649 0 600 4 073 0 577 6 494 0 534 7 996 0 513 9 690 11 599 0 474 190 311 else A ot Total Present Worth 399 431 Salvage Value 176 716 Life Cycle Cost 222 715
62. 4 Description of Treatments 4 1 Overview Treatments are activities performed on the bridge deck to address corrosion related distress These activities may be either preventive or corrective in nature and may encompass different techniques e g portland cement concrete PCC patching overlays sealers cathodic protection As new technologies become available they may also be defined as treatments to investigate for example their potential cost effectiveness In order to encompass a wide range of treatments CORRODE adopts a flexible input format that asks you to describe the essential characteristics of a treatment e g its nominal life costs the production rate at which it can be installed and so forth CORRODE does not ask you however to classify the treatment in any way e g to group it as an overlay or a sealer for two reasons e Treatments can be defined as a combination of techniques e g patching of distressed areas plus overlay or sealer applied over the entire deck area As new methods are developed or experimental materials are tried it may not be possible to classify them according to conventional techniques You must therefore ensure that the treatments specified are appropriate to the respective bridge deck and compatible with its elements and materials Examples of compatibility considerations are given in Tables 1 and 2 The data that describe a treatment are grouped in treatment files much as
63. Corrosion Date 251 Remaining Corrosion Data 256 Viewing Results id seca 1d Robe dca how a Rc ones ek ees 264 xlii Part I Table 1 Table 2 Part I Table 4 1 Table 6 1 Table 6 2 Table 8 1 Table 8 2 Part HI Table 4 1 Table 4 2 Table 5 3 List of Tables Page Comparison of Evaluation Schemes 21 Input Data for Example Treatments 52 Number of Tests and Samples 108 Correlation of Rate of Deterioration and Resistivity 127 Estimates of Surface Level Chloride Content in 10 Years 127 Selection of Compatible Deck Treatment Alternatives 147 Selection of Compatible Structural Treatment Alternatives 148 Selection of Compatible Deck Treatment Alternatives 232 Selection of Compatible Structural Treatment Alternatives 233 Number of Tests and Samples 252 XV List of Flowcharts Part I Appendix A Page Flowchart 1 General Technical Methodology for Technical Goal One 60 Flowchart 2 General Information Module ees 61 Flowchart 3 Protect Information Module ee eens 62 Flowchart 4 Present Information Module eee recess 63 Flowchart 5 Time To Modil 25 3202 2m dore POR GS ACRIOR 64 Flowchart 6 Post Deterioration Submodule eese 65 Flowchart 7 Calculation One Submodul
64. E will issue a Beep Please refer to the message at the bottom of the screen indicating what you should do next Context sensitive help For each option or field CORRODE displays a brief message indicating what you need to do next at the bottom of the screen For more detailed information and assistance press F1 e Finishing After you have selected options or input your data within a data form you may save your work by pressing F10 If you wish to quit without saving any recent changes you may have made press Escape To exit any input form or menu with no action taken press Escape e Cannot close If you are trying to save your work F10 or to quit Escape and CORRODE won t let you accompanied by a Beep this means that a field contains an invalid entry Please be sure that all mandatory fields have valid data Also check the message bar at the bottom of the screen for hints on what needs to be done Exiting CORRODE When you are completely done with CORRODE and wish to quit the program enter Alt Q If the system does not quit press Escape one or more times to return to the main menu bar and press Alt Q again Please be sure however that you have saved all your work beforehand by using the F10 key A guide to typically required keys is displayed in a message bar at the bottom of the screen or at the bottom of data entry forms 1 6 Screen Layout CORRODE includes a number of different screen displays appropriate to the pa
65. Is not Deterioration Has Not Known Begun 106 3 the concrete has not yet shown the first sign of corrosion induced deterioration testing the concrete for resistivity 4 2 Number of Tests and Samples The procedures in Table 4 1 are given with suggestions for the number of tests and samples to obtain from various bridge components 43 Test Descriptions The following chapters discuss the individual evaluation methods Visual Examination A visual examination of the concrete surface is used to determine the extent of deterioration and forms the basis for the subsequent concrete condition surveys The visual examination described here is not related to the bridge survey system adopted by Federal Highway Administration The visual examination notes both corrosion and non corrosion related deterioration It should note size location and orientation of 1 spalls 2 patches temporary and permanent 3 scaling 4 pop outs 5 cracks and 6 wheeltrack wear only bridge decks These items should be shown on a sketch A grid layout is established on the concrete surface to map concrete deficiencies and to determine their magnitude based on a percent of surface area The severity of the deterioration should be determined quantitatively during a visual examination by simply measuring the depth of spalls scaling and wheeltrack wear Exposed and corroding reinforcing steel should also be noted The visual examination generat
66. L Thus 0 5 C C t t C ESL and C C ta 19 2C Step 4 Use Equation 12 6 to estimate C the rate of corrosion corresponding to t age of concrete at time of treatment years milli amperes per square foot change t to t in Equation 12 5 to obtain Equation 12 6 C t t C t t t Equation 12 6 Step 5 Estimate the effective service life of the newly treated concrete ESL years from Equation 12 7 assuming the rate of corrosion after the treatment will roughly remain constant a behavior generally expected of sealers coatings asphalt concrete membrane systems or rigid overlays See Figure 12 7 for the derivation of Equation 12 7 ESL Cn C ta t 2 C Equation 12 7 Note that if the concrete was also previously treated with sealers coatings asphalt concrete membrane systems or rigid overlays in the absence of background rate of corrosion data it may be assumed C GC C and Equation 12 7 will give ESL t t Equation 12 8 For more accuracy users may adjust the effective service life obtained from Equation 12 8 when the new treatment is not the same as the previous treatment The adjustment should be on the basis of the experience and or the results of SHRP research by Weyers et al As a default the effective service life obtained from Equation 12 8 may be increased 30 percent if the new treatment is a concrete overlay and the previous t
67. ORRODE is based on a technical analysis of bridge deck corrosion and related distress and an economic evaluation of different protective or corrective strategies which have been developed The system requirements for data input conform to these technical and economic analyses as described in Part I of this document Guidelines governing required data and default values are as follows e The data requested in CORRODE s input forms should be interpreted as required whether for an analysis or for file identification The only exceptions are comment fields which are for your convenience they are always optional never required e CORRODE uses two mechanisms to guide your input of data so that it is relevant to the specific conditions and point in the history of each bridge deck 215 216 1 CORRODE controls access to the input fields allowing you to provide input only to those fields that are relevant Fields that are not relevant appear in a contrasting color and you are blocked from entering data in these fields 2 CORRODE determines the appropriate input forms to display based on data input to that point For example forms to accept values of certain data are displayed only if you indicate that such data are available Also the display of certain input forms for corrosion data is predicated on CORRODE s analysis of whether or not corrosion has already taken place in the bridge deck Default values are provided as the initia
68. OS you may inadvertently change them or delete them in ways that will disable them for use by CORRODE Messages to the effect that files are not available may result if these files are corrupted See also the section below on user id and path conventions All management of files should be done through CORRODE s command structure Previous chapters have already introduced you to several of CORRODE s file management commands e g creating and editing bridge and treatment files in Chapters 3 and 4 as well as copying treatment files in Chapter 4 the creating of analysis files in Chapter 5 and creating and deleting report files in Chapter 6 In this chapter the remaining file management option will be introduced the overall DELETE command DELETE is the last option on the main menu bar at the top of the screen 7 2 The DELETE Option The DELETE submenu lists four types of files e Bridge files select this option to delete files created in BRIDGES Corrosion files select this option to delete corrosion files created in ANALYSES e Treatment files select this option to delete files created in TREATMENTS e Life cycle files select this option to delete life cycle cost files created in ANALYSES 269 These submenu options all operate in a similar way e Choose the type of file to delete by pressing Enter CORRODE will list the names of currently existing files for the selected bridge that bear your id i e that are identi
69. PART III USER MANUAL FOR CORRODE 1 CORRODE Basics 1 1 What is CORRODE The CORRODE system was produced as part of this SHRP Project The objective of this project was to develop a procedure to evaluate different preventive or corrective strategies for mitigating corrosion of reinforced concrete bridge decks This analysis entails both an accounting of the corrosion mechanism itself and its progression to visible signs of distress and the evaluation of alternative treatments within a life cycle cost framework By applying this procedure you are able to analyze this problem in the following stages e To determine the current state of corrosion of a bridge deck and estimate its future deterioration rate of increase in distress over time e To apply a life cycle cost analysis to compute the optimal time i e the year in which total life cycle costs are minimized for performing a given treatment that you define e To compare the optimal times and costs of various preventive and corrective strategies to arrive at the most economical alternative This project has embodied this analysis in two ways a handbook in Part II and a computer system CORRODE These two solutions are based upon the same basic methodology but they stand alone in that you may use one without reference to the other This manual accompanies the CORRODE computer system it is intended to help you understand the various system options available and to provi
70. RP research by Cady and Gannon If overlay debonding is significant the most cost effective treatment may be obtained considering factors which are not covered in this methodology B 3 Cover Depth over Reinforcement Using a Cover Meter Magnetic Flux Device This device uses a magnetic field to detect reinforcing steel within hardened concrete It can determine the location orientation size and depth of the bar The accuracy of the device in measuring the depth of cover decreases as the depth of cover increases Magnetic particles in the concrete can influence the measurements Thus a correction factor should be obtained by exposing the bar at one location and measuring the actual depth Usually the correction factor is obtained at a location which can later serve as the half cell test bar ground connection If the bar size is not known the depth cannot be read directly from the scale therefore the following technique is suggested 1 Locate the bar in the test area 2 Place a two by four or other non metallic spacer between the probe and the concrete surface 3 Record possible bar size and depth combinations 285 4 Correct readings for the thickness of the spacer by subtracting its thickness 5 Place the probe directly on the concrete surface and record possible reading The bar size for which the same cover depth is obtained in steps four and five is the correct result B 4 Reinforcing Steel Electrical Continuity
71. SHRP S 377 Life Cycle Cost Analysis for Protection and Rehabilitation of Concrete Bridges Relative to Reinforcement Corrosion Ronald L Purvis P E Khossrow Babaei P E Wilbur Smith Associates BTML Division Falls Church Virginia Kenneth C Clear Kenneth C Clear Inc Boston Virginia Michael J Markow P E Cambridge Systematics Inc Cambridge Massachusetts Strategic Highway Research Program ERN National Research Council Washington DC 1994 SHRP S 377 ISBN 0 309 05755 8 Contract C 104 Product No 2037 2038 Program Manager Don M Harriott Project Manager Joseph F Lamond Consultant John P Broomfield Program Area Secretary Carina S Hreib Production Editors Cara J Tate February 1994 key words bridges corrosion cost effectiveness life cycle protection rehabilitation reinforced concrete Strategic Highway Research Program National Research Council 2101 Constitution Avenue N W Washington DC 20418 202 334 3774 The publication of this report does not necessarily indicate approval or endorsement by the National Academy of Sciences the United States Government or the American Association of State Highway and Transportation Officials or its member states of the findings opinions conclusions or recommendations either inferred or specifically expressed herein 1994 National Academy of Sciences 1 SM NAP 294 Acknowledgments The research described herein was supported by
72. Steel Electrical Continuily Electrical continuity of the reinforcing steel should be known prior to conducting certain tests or applying certain treatments Electrical continuity can be determined by measuring the resistance between widely separated steel components Low resistivities indicates continuity Chloride Profiles AASHTO T260 84 or SHRP Modified Test Method This test determines the chloride content of concrete Concrete powdered samples are collected with a vacuum bit near the concrete surface 0 25 inch to 0 75 inch 0 6 centimeters to 1 9 centimeters depth and at the level of the reinforcing steel the bottom 0 25 inch 0 6 centimeters of concrete cover Where a concrete overlay is applied concrete surface is the surface of the overlay The SHRP Standard Test Method for Chloride Content in Concrete Using the Specific Ion Probe is documented in Appendix F of Cady and Gannon In the SHRP test method which is a field method the powdered samples are dissolved in and stabilized by two solutions A probe is then inserted into the mixture and the readings are recorded in the field Calculations convert readings into chloride content expressed as a percentage of concrete weight AASHTO 1260 84 test method may be used for chloride content determination Corrosion Potential Survey ASTM C876 This procedure ASTM C876 determines the potential for the existence of reinforcing steel corrosion through measuring the electri
73. Total Agency Cost 21 000 56 000 77 000 Strategy Treat at t Use Equations 11 1 through 11 3 to decompose the condition index of S 33 5 CL 258S CL 5 33 5 167 5 gt 100 then CL 100 DELAM 8 5 S CL 2 5 7 5 N DELAM 8 5 x 33 5 100 2 5 7 5 4 42 2 SPALL DELAM N SPALL 422 4 10 5 Total Area Deteriorated 42 5 10 5 53 1 Removing and patching concrete 53 percent of 10 000 square foot at 35 per square foot 185 500 2 Concrete overlay 10 000 square feet at 5 60 per square foot 56 000 Total Agency Cost 185 500 56 000 241 500 Use the same agency cost when treatment is repeated at S with sufficient accuracy Strategy Treat between t and t Use Equations 11 1 through 11 3 to decompose the condition index of S 17 9 CL 5S CL 5 17 9 89 5 DELAM 8 5 S CL 2 5 7 5 N 202 DELAM 8 5 x 17 9 89 5 2 5 7 5 4 14 3 SPALL DELAM N SPALL 14 3 4 3 6 Total Area Deteriorated 14 3 3 6 17 9 1 Removing and patching concrete 17 9 percent of 10 000 square feet at 35 per square foot 62 650 2 Concrete overlay 10 000 square feet at 5 60 per square foot 56 000 Total Agency Cost 62 650 56 000 118 650 Use 241 500 as agency cost when treatment is repeated at S with sufficient accuracy see previous strategy Step 4 User Cost Prior to Treatment To find user costs prior to treatment see part G abo
74. YSES option The life cycle cost analysis also requires that you have already selected a bridge for analysis in BRIDGES and that you have already defined a treatment in TREATMENTS e Once both the corrosion and the life cycle cost analyses are run you may request displays of these results at any time thereafter using the REPORTS and the GRAPHS options Reports and graphs may be obtained at any time so long as the results files for the particular runs are retained e Files that are not to be retained can be deleted using the procedures in DELETE As you become more familiar with the system you will be able to use these guidelines to advantage For example you may begin building a library of information about your bridge inventory by creating a bridge file for each deck that you may wish to study You may also wish to create a standard hypothetical bridge to which you attach standard definitions of treatments that can later be copied and tailored to specific decks Ultimately you may want to test several treatments at one time so that you may compare their life cycle costs and recommended time of performance All of these objectives can be accomplished by using the system s features described in later chapters These guidelines provide a general overview of system capabilities and the typical order of steps that you may follow Details on each option in the main menu are presented in later chapters as follows e Chapter 3 discusses bri
75. a treatment will influence the estimate of the duration of traffic disruption thereby affecting the incremental user costs during the project period that will also be accounted for in the life cycle cost analysis Data should be entered only for those cost and time components that are deemed relevant to the particular treatment being defined If cost and time components are not relevant a zero should be entered for both The discussion below refers to various measures of bridge deck condition or distress Technical explanations of these are given in Chapter 5 in the discussion of corrosion and life cycle cost analyses Fixed cost and time required fixed items of the project are those items whose time and cost are not a function of the deck area or amount of distress to be repaired The cost is entered as a lump sum in dollars The 239 240 time is entered in days Include a time estimate only if the activity causes a restriction to the normal flow of traffic across the bridge Examples of items that can be included here are mobilization and setup of traffic controls Deck cost and productivity components of cost and productivity related to any work that will be performed on the total area of the deck e g placement of a sealer or an overlay over the entire deck area The unit cost entered here is in dollars per square foot of deck area the productivity is expressed in square feet accomplished per day For example assume a deck
76. an upper bound for CORRODE s assessment of the actual predicted life of the treatment The actual prediction will be based on considerations involving the corrosion 241 rate model which may reduce the estimated life below the value you input but will never increase it If you have no information on the nominal life of the treatment estimate this value using the methodology developed in the report for SHRP Project C 103 Corrosion model the change in the corrosion rate that is effected by the treatment These changes are characterized numerically by a K factor that is explained in the next item Five options are specified for your selection 1 the corrosion rate continues to increase at the same slope as prior to the treatment K 1 2 the corrosion rate continues to increase but at a lesser slope than prior to the treatment 0 K 1 3 the corrosion rate remains at the level that existed just prior to the treatment and neither increases nor decreases with time K 0 4 the corrosion rate declines somewhat from the level that existed prior to the treatment K 0 or 5 the corrosion rate reduces to zero for some period of time refer to the Life with no corrosion input item below To a large degree this selection depends on the impact of the treatment on the chloride concentration in the concrete and its effect on the rebar e Kfactor a quantification of the change in corrosion rate indicated by your selection of a co
77. ased on the level of snowfall and or exposure to marine environment as shown in Table 6 2 Step 11 Determine the set of data corresponding to the first sign of deterioration using the estimate of surface chloride content in 10 years as shown below t age of the concrete at time to first deterioration years Equation 6 2 or Figure 6 1 S condition index at time to first deterioration 1 9 126 Table 6 1 Correlation of Rate of Deterioration and Resistivity ohm cm t4 Table 6 2 Estimates of Surface Level Chloride Content in 10 Years Snowfall Range inch Marine Exposure and Distance Future Surface Chlorides in 10 from Seawater years Whichever is Greater NO Z t 10 tor 0 04 percent of concrete weight 3 to 12 NO Z t 10 tor 0 10 percent of concrete weight 0 to 12 YES gt 25 ft Z t 10 tor 0 10 percent of concrete weight 0 to 12 YES lt 25 ft Z t 10 tor 0 25 percent of concrete weight gt 12 NO Z t 10 tor 0 25 percent of concrete weight gt 12 YES gt 25 ft Z t 10 tor 0 35 percent of concrete weight gt 12 YES lt 25 ft Z t 10 tor 0 45 percent of concrete weight 1 One inch is 2 54 centimeters and one foot is 0 305 meters 2 Z is the surface chloride content percent of concrete weight divide by 0 025 to convert to pounds per cubic yard or divide by 0 042 to convert to kilograms per cubic meter as defined in Equation 6 2 t is the duration of expos
78. ases at a Slower Rate 169 Nomogram to Determine Effective Service Life of Concrete After Treatment When Rate of Corrosion Levels Off ou dineeeesib ue ulus a aci diit dt a e MUR e a Oe Sapa 170 Figure 12 6 Figure 12 7 Figure 13 1 Figure 13 2 Figure 13 3 Figure 13 4 Figure 13 5 Figure 14 1 Figure 14 2 Figure 14 3 Part HI Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Nomogram to Determine Effective Service Life of Concrete After Treatment When Rate of Corrosion Decreases 172 Trend of Corrosion Process After Treatment 174 Concrete Repaired Rehabilitated and or Protected Previously Worksheet for Life Cycle Cost 181 182 Example of Tabulated Treatment Strategy Treat at t 183 Example of Tabulated Treatment Strategy Treat at 184 Example of Tabulated Treatment Strategy Treat between t and t 185 Discount Factors 439 ecc obe va gx eaa b VA eR SS 189 Worked Example of Tabulated Treatment Strategy Treat at t 208 Worked Example of Tabulated Treatment Strategy Treat at ta 209 Worked Example of Tabulated Treatment Strategy Treat between t and t i24 sk y a 210 Mun Menu Options 12 224 urasqa dee RR a oo e Ron 221 Bridge Menu Options 4 4 EPXRU ES RADO IRURE wae 226 Treatment Menu Options 2 2 62 a ER S e ke Ee 234 Analysis Menu Options 248 Additional Forms for Input of
79. at are deteriorating or are subject to deterioration Part Two presents the methodology in the form of a handbook for highway agencies The handbook includes nomograms tables and other aids to facilitate the selection of the most cost effective strategy The methodology has also been incorporated into a microcomputer program Part Three of this report documents the microcomputer program s user s manual explaining the system s features options and displays Contents Page ADSI EE sus um p tas miu ve u apup m ans sh ne Pr 1 Executive Summary scra kene ow de WE RUE acl OE HR Uu Sel de deo Q G g k ee Ge te os 3 Glossary Of Variables 5 e ss sua pa ONIS EEE EA Ree d 5 Part I Methodology Chapter 1 OVEIVICW 4 zu Tum qo B EY oq ZS Q Ai PAE RS gh ee Rr 9 Chapter 2 Technical Goal One Condition Index Versus Time 13 Chapter 3 Technical Goal Two Decomposing Condition Index 20 Chapter 4 Technical Goal Three Cost and Maximum Service Life of Treatment 4 4 3 52a 6 6 eho q Se OSH pauco ECCE 31 Chapter 5 Technical Goal Four Condition Index Versus Time After Treatment s uq uapa we As Spe qe d g ur dd ds eh 35 Chapter 6 Technical Goal Five Life Cycle Cost Analysis 47 Appendix A Flowcharts 59 Appendix B Report Format Example 71 Appendix C Condition Index 75 Appendix D Time to Deteriorat
80. ation 11 19 92 Expert Task Group Neal S Berke W R Grace and Company Ken Fryer Missouri Highway and Transportation Department Tony Garcia Florida Department of Transportation Crawford F Jencks Transportation Research Board Theodore H Karasopoulos Maine Department of Transportation James E Roberts California Department of Transportation Arun M Shirole New York Department of Transportation Paul Virmani Federal Highway Administration 8 9 93 e f a aa ee sn t RIT ds nette
81. ation rate will be low medium or high should be possible and standard curves can be assigned to each rate designation This assignment can be based on the 25 wet resistivity of the concrete A suggested test method is presented in Appendix E The following table provides decision data Distress Rate Resistivity Years to Condition ohm cm Index of 45 High lt 7 500 t 10 Medium 7 500 to 30 000 t 20 Low 30 000 t 35 From the table above t4 the concrete age to reach the index of 45 S 45 prior to rehabilitation can be defined and output to the cost analysis in lieu of t and S The estimates in the table above are based on experience Examples and a sample plot are presented in Appendix E Repair Information Module Flowchart 10 This module covers concretes which were repaired in the past in response to corrosion induced damage The past repair includes patching salt contaminated concrete may be left in place or removed sealing overlay and or membrane It does not include cathodic protection These concretes have t age of concrete at the first signs of deterioration in the past Therefore there is no need to calculate t or to define t age of concrete at the initiation of corrosion To accomplish Technical Goal One however the user needs the following information 1 Year in which the previous repair was performed 2 Details of the previous repair including a percent bar level chloride contaminati
82. ay be used for low slump dense concrete as well After you have input these values press F10 to save the selection of this protective system 1f you press Escape CORRODE will return you to the list of protective systems but will not have selected the concrete overlay 253 10 Full depth silica fume concrete enter the rapid permeability test RPT coulomb value of the silica fume concrete deck Exit with F10 to save the selection or with Escape to ignore it Silica fume concrete overlay enter the thickness inches and the water cement ratio decimal fraction of the silica fume overlay Exit with F10 to save the selection or with Escape to ignore it Asphalt concrete AC overlay with waterproof membrane enter an estimate of the additional years protection afforded by this protective system Exit with F10 to save the selection or Escape to ignore it Penetrating sealer enter an estimate of the additional years protection afforded by this protective system Exit with F10 to save the selection or Escape to ignore it Surface protective coating enter an estimate of the additional years protection afforded by this protective system Exit with F10 to save the selection or Escape to ignore it Corrosion inhibitor concrete enter an estimate of the additional years protection afforded by this protective system Exit with F10 to save the selection or Escape to ignore it Other systems enter an estimate of the add
83. bmodule 23 Starting with the Post Deterioration Submodule Post Deterioration Submodule Flowchart 6 The submodule asks for technical input data regarding the time to deterioration Question 1 From the present data it has been determined that this member is_showing signs of corrosion induced deterioration What year was chloride induced corrosion first noticed Possible answers are Year or Don t Know If a year is given it is accepted and t Year Given minus Year Built no other background data are requested and the user proceeds If the answer is Don t Know proceed to the Calculation One Submodule knowing that t must lie between the Year Built and the Present Calculation One Submodule Flowchart 7 In this submodule the user calculates the past ta Input data include that from the General Protect and Present Information Modules as follows 1 Adjustment of ta if any because of a protective system installed at the time of initial construction 2 Average standard deviation and 10th percentile concrete cover 3 Water cement ratio of the concrete between the surface and bar The module then requests data on the surface chloride level at present to calculate t for the concrete The methodology recommends that at least eight surface chloride levels from 0 25 inches 0 6 centimeters to 0 75 inches 1 9 centimeters be determined per member or per 5 000 square feet 465 square meters whichever resul
84. by Chloride 80 74 Appendix C Condition Index 75 Condition Index S Three major factors influence the corrosion condition of the structure at a given time Percent bar level chloride contamination CL e Percent delamination DELAM 9 Percent spalling SPALL Of these spalling is the most important delamination is second and the bar level chloride contamination is the least important when considering treatment at a given time The importance of each of these variables in triggering treatment was defined as follows e Spalling is three times more important than delamination e Delamination is 2 5 times more important than bar level chloride contamination _ CL 2 5 DELAM 7 5 SPALL S 8 5 where CL percent of bar level samples with chlorides higher than the corrosion threshold value DELAM percent of area with nonvisible undersurface fractures only SPALL percent of area with visible deterioration 8 5 a normalizing factor 76 Evaluate ten bar level chloride samples per member or per 5000 square feet 465 square meters whichever results in the greater number of data points Sampling depth shall be between the cover depth and cover depth plus 0 5 inches 1 27 centimeters at each location Determine whether or not each value is greater than or equal to or less than the threshold for corrosion by weight of concrete 0 035 percent 350 ppm plus any chloride locked in the aggregate plus any c
85. by the CORRODE system in any way it is strictly for your convenience You may use this field to describe for example more detailed information about the bridge deck in question notes on current deck condition the date and findings of the most recent inspection or comments on the types of treatments you will be investigating e Year re constructed the calendar year in which the deck concrete was placed as the result of initial construction or replacement e Deckarea the plan area of the bridge deck in square feet e Traffic the two way traffic volume vehicles per day or annual average daily traffic AADT through the analysis period If traffic growth or decline is anticipated enter the estimated average value over time 228 e Normal capacity the two way capacity of the bridge in vehicles per day or AADT under normal operating conditions i e with no construction zones or other temporary restrictions or devices Average crossing time the average time for a vehicle to cross the bridge in minutes accounting for the variation in traffic volumes throughout the day and year For example a weighted average of peak and off peak conditions would suffice User cost coefficient the coefficient K in the formula given below representing average dollars per vehicle accounting for the mix of vehicles in the traffic stream User cost exponent the exponent n in the formula given below representing the rate of i
86. cal potential of the reinforcing steel It may be performed if 10 percent of the chloride samples at the depth of the steel are greater than the corrosion threshold chloride content The procedure for administering this test follows 1 Establish a grid on the concrete surface 2 Provide an electrical connection to the steel ground 110 3 Place a half cell corrosion detection device on the concrete surface at the grid points 4 Record the electrical potential readings Note that the test cannot be conducted in the absence of the electrical continuity of the reinforcing steel This procedure obtains the location of highest half cell potentials peak negative potentials for the subsequent rate of corrosion testing The location of highest potentials can be obtained in the field by scanning the concrete surface around the anodic areas with a half cell device The locations of anodic areas are obtained by plotting the grid half cell potentials and drawing equipotential contour lines The corrosion potential survey is not recommended for epoxy coated or galvanized reinforcement This is because epoxy coated bars are electrically insulated from each other and readings on galvanized bars indicate the potential of the zinc coating Also the test cannot be conducted where concrete is overlaid with a dielectric material such as a membrane polymer material or asphalt unless the asphalt is saturated Rate of Corrosion Measurement Th
87. cost will be determined Press Enter when finished e Discounting rate enter the discount rate in percent to be used in the analysis Your agency may have already established the value of discount rate to be used in economic analyses of project alternatives The discount rate at the federal level is set by the Office of Management and Budget If no information on discount rate is available use the guidance in the AASHTO Red Book e Results file the results of the current life cycle cost analysis will be stored in the file you identify here Choose a name that conforms to DOS naming conventions If the name you enter matches that of a previously defined life cycle cost file CORRODE will ask you OK to overwrite existing file If you respond no N CORRODE will return you to the 261 entry field so that you may modify the name you had entered If you respond yes Y CORRODE will proceed with the analysis all previous contents in the results file will be Jost Life Cycle Analysis Results When you have completed data input press F10 CORRODE will automatically begin the life cycle cost analysis When the analysis is completed CORRODE will display a screen entitled Life Cycle Cost Analysis Solution This screen gives the optimal time to perform the treatment you had selected earlier for the bridge and the associated corrosion model that you also selected A message informs you that reports and graphs can be obtained for thi
88. ct the effective service life of the treated concrete As noted in Figure 1 the treatment can be forced to occur at the present point in time Best Action Now or the system can define the best action at the best time in the future by minimizing life cycle costs Regardless of the approach taken the effective service life of each candidate treatment must be known SHRP research indicated that for at least some treatments the life of the treatment was not primarily determined by the treatment itself but depended on characteristics of the concrete which was repaired Typically non electrochemical treatments experience shorter lives when placed on bridge components with much remaining salty concrete and high bar corrosion rates than when placed on components with low chlorides and low corrosion rates This information became the primary determinant of the after treatment approach in this work For example an overlaid deck does not have a fixed effective service life rather it has a variable effective service life dependent on the corrosion state of the reinforcing steel when the overlay is placed Because of this finding after treatment approach was developed involving the corrosion rate of the reinforcing steel The approach is based on knowing the corrosion rate versus time and on repeating of each chosen treatment after an additional amount of cumulative corrosion corrosion rate multiplied by time has occurred The additional amount of cumu
89. cted previously and with a special protection built at the time of initial construction A special protection is a positive protection against corrosion of reinforcing steel other than quality conventional concrete cover Typical concrete repair rehabilitation and protection systems are presented in Chapter 8 A predicted concrete condition index is calculated through a performance equation which relates the condition index to the age of concrete The performance equation used in the methodology which represents S shaped curves is given below S 100 1 A exp Bt Equation 6 1 where S concrete condition index predicted for concrete age of t A B constants controlling the rate of deterioration and the shape of the curve t time since initial construction age of concrete Parameters A and B are determined from site specific data One set of data i e condition index and corresponding age relates to the present or time of condition 117 survey if different The other set of data relates to the time of first sign of deterioration unless the concrete was repaired rehabilitated and or protected in the past See Section 6 1 In that case the second set of data relates to the time of repair rehabilitation and or protection By convention the concrete condition index at the time of first signs of deterioration Sa corresponds to 15 percent chloride contamination at bar level and 0 5 percent delamination Thus S
90. d as described in a section below Also if yes is entered CORRODE suppresses certain other data items in the input form since they will not be needed in the corrosion analysis e W C deck concrete enter the water cement ratio of the deck concrete as a decimal fraction e Number of cover data enter the number of cores taken to determine thickness of the concrete cover over the rebar After you enter this number and press Enter CORRODE displays an input sheet in which you enter each thickness observation in inches CORRODE will use this information to compute the mean and standard deviation of the thickness distribution and the estimated thickness at the 90 percent confidence limit When you have finished entering the thickness data press F10 Protective system indicate N or Y whether a protective system has been installed previously for this bridge deck A protective system significantly reduces the rate of ingress of chloride ions nto concrete Protective systems are limited to those decks that are not critically contaminated with chloride Sealers coatings and polymer overlays are normally thought of as protective methods However hydraulic cement concrete overlays such as low slump dense micro silica and latex modified concrete can also be used as protective methods If your response is Y a separate input form will be displayed as described in a section below Refer to the section below for a list of installed techniques
91. d determine the maximum tolerable condition index S based on the structural features of the component and or the ride quality of the deck The period of time between the present time and time corresponding to S is the treatment consideration period This is expressed in the following equation Treatment Consideration Period t t Equation 7 1 where t age of concrete when condition index is S determined from the following equation or the performance curve Figure 7 1 years t In 100 S A S B Equation 7 2 t age of concrete at present years The rest of this manual should be used to determine the timing of the treatment within the treatment consideration period as well as the type of the treatment for maximum cost effectiveness 131 Figure 7 1 Concrete Performance Curves B 0 10 e e co b WY P S xepuy uo jpuo c Concrete Age Years t 132 Continued Concrete Performance Curves B 12 Figure 7 1 EE S S IR ee en ee HERE SESI IINE 50 S x pul uopipuoo Concrete Age Years t 133 Figure 7 1 Continued Concrete Performance Curves B 14 Poel Ez FERE NUNT SIN EXCNOMND OS RNC NN PONES js mop lom mee 2 cg Z 2 a SE TUNN i My Concrete Age Years t S x pul uonipuoo 134 Figure 7 1 Continued Concrete Performance Curves B 16 S x pul uonrpuog Concrete Age Years t 135
92. de tips on useful approaches Chapters 1 and 2 provide an overview of the system s capabilities and instruct you in the basic techniques of navigating through the system selecting from the options available and performing different tasks data input executing commands etc Chapters 3 through 7 provide additional details about each option or feature to help you understand the implications of each choice In most cases once you have mastered the basics you will find operating the system very easy and intuitive 211 You are encouraged to explore the system s features and operating style as soon as you have read Chapters 1 and 2 and scanned the remaining chapters to get a feel for the various capabilities of the system and the scope of its analyses You may want to develop some example problems and work them through the full range of the system s features As you do so please observe how the system handles certain critical tasks and functions e g how it relates data files to different bridges and its general approach to creating and deleting files Please consult the manual for special instructions and notes regarding these operations particularly in the deletion of files 1 2 Installing CORRODE CORRODE is easy to install Please be sure you have the latest version of a CORRODE Install Disk and follow these guidelines e Enter DOS on your system and change to the directory on your hard drive or network system file server in which y
93. dge descriptions and other capabilities of the BRIDGES options e Chapter 4 explains how to define treatments using the TREATMENTS options e Chapter 5 covers both the corrosion analysis and the life cycle cost analysis that are provided in ANALYSES Chapter 6 describes how analysis results may be displayed using features in REPORTS and GRAPHS 223 e Chapter 7 covers DELETE and other aspects of file management in CORRODE 224 3 Bridge Descriptions 3 1 Overview The description of general bridge characteristics and their selection for data input and analysis are handled through the BRIDGES option in the main menu The BRIDGES submenu provides three options Selecting a bridge e Editing a previously defined bridge file and Creating a new bridge file These options are illustrated in Figure 2 and will be explained in more detail below Following these explanations is a description of the basic information that you may input to the bridge file 3 2 Selecting a Bridge A bridge must be selected before its file can be edited or used in any analysis performed by CORRODE A bridge must also be selected before other files relating to it e g treatments reports can be defined or used since these data must always be assigned to a specific bridge In this way it is always clear to you and to CORRODE which file is being edited or applied in an analysis or to which bridge a file should be assigned The name of
94. e eee eee 66 Flowchart 8 Pre Deterioration Submodule eese 67 Flowchart 9 Calculation Two Submodule eee 69 Flowchart 10 Repair Information Module een 70 XVII Abstract A systematic methodology is presented for highway agencies to use at the project level to determine the most cost effective treatment and its timing for specific concrete bridge components that are deteriorating or are subject to deterioration The methodology is set forth in the form of both a handbook and a computer program The methodology in its present form applies only when the predominant concrete deterioration is associated with chloride induced corrosion of the reinforcing steel The methodology is designed to be flexible and can be tailored to suit the needs of individual highway agencies Executive Summary The deterioration of concrete bridges is a major problem in the operation of the nation s highway system The cost of repairing or replacing deteriorating bridges is one of the most expensive items faced by highway agencies and it is increasing rapidly The main cause of the deterioration is the use of salt in winter maintenance operations The salt penetrates the concrete and corrodes the reinforcing steel eventually resulting in internal cracking and surface spalling of the concrete The deterioration occurs on all concrete bridge components including decks superstructure elements and sub
95. e O 5 Le ase a 99 S DE lt F RoR E E Ratio of Condition Index to Maximum Condition Index S S_ 11 Decomposing Concrete Condition Index In order to estimate agency costs and user costs associated with a treatment Chapter 9 and 10 the amount of concrete repair removing and replacing deteriorated and possibly contaminated concrete needs to be predicted at the time of treatment The user can predict the amount of deterioration and contamination in the future by decomposing the future concrete condition index S into its component parts i e CL DELAM and SPALL see Chapter 5 Use the following procedure to decompose concrete condition index 11 1 Assumptions 1 Chloride contamination CL increases 5 percent for each index increase of one unit 2 For all deck concrete except those with 1 inch 2 54 centimeters or thicker concrete overlays DELAM is 4 times SPALL For all deck concrete with 1 inch or thicker bonded concrete overlays DELAM is 8 times SPALL 3 For all non deck concrete except those with 1 inch 2 54 centimeters or thicker concrete jackets or shotcrete DELAM is 8 times SPALL For all non deck concrete with 1 inch 2 54 centimeters or thicker concrete jackets or shotcrete DELAM is 16 times SPALL 11 2 Procedure valid only for weighting factors used in Equation 5 1 CL 5S andCL lt 100 Equation 11 1 DELAM 8 5 S CL 2 5 7 5 N Equation 11 2 where N
96. e Since the current level of distress is small treatments that can correct this distress or prevent further distress at relatively low cost are preferred Effect of Parameter Variation The parameters identified in Table 2 can be varied to assess their impact on the solution To give one example we investigated the effect of an increased traffic volume The average daily traffic of 25 000 in Table 2 was increased to 55 000 just below the bridge capacity during the treatment project Results and comparison with the original case are shown in Figure 12 using the overlay treatment as an example The increase in traffic results in an earlier optimal time of treatment from 24 to 23 years and a somewhat higher minimum total cost Both of these effects are expected and consistent with the problem formulation A higher traffic volume increases the penalties of a deck in bad condition since more users experience this condition prompting an earlier treatment The higher total costs are associated with several effects e The earlier performance of the treatment which means that the agency costs are not discounted as much 56 The greater number of users experiencing a deteriorating deck condition Interactions among users themselves that is if traffic speed is reduced somewhat because of distress in the wheelpaths on the deck the greater number of users increases the degree of congestion exponentially 57 Discounted Costs Thousands
97. e 4 The overall evaluation has four purposes 1 Obtain an overall measure of present condition 2 Define data to predict time to deterioration 3 Develop data to predict future deterioration 4 Define the applicability and cost considerations for selected treatments 18 Figure 4 Evaluation of Field Structures CORROSION INDUCED DISTRESS Visual Survey Record Percent Spalling OTHER NON CORROSION RELATED DISTRESS Delamination Survey Calculate Percent COVER CONTINUITY AND CHLORIDES Bar Cover i Bar Level Chlorides and Continuity f Surface Level Chlorides f CORROSION Grid Half Cell Potentials Bar Level Chloride Content Greater than 0 03596 yes or appropriate value Rate of Corrosion Testing at Anodic Half Cell Sites CONDITIONAL TESTS Chloride Permeability Concrete Resistivity When Representative B When Corrosion W C Ratio Is not Known 1 Has Overall Measure of Present Condition Obtained Data Available to Predict Time to Deterioration Data Available to Project Future Deterioration 19 As a result the evaluation varies somewhat from that defined in SHRP research by Cady and Gannon However this variance is not a conflict in that the SHRP condition evaluation manual only involves the first item above i e measure present condition Table 1 compares the evaluation schemes of this research project and of the SHRP condition evaluation manual and notes the
98. e SHRP Standard Test Method for Determining Instantaneous Corrosion Rate of Uncoated Steel In Reinforced Concrete is documented in Appendix A of Cady and Gannon The test should be conducted at locations of highest corrosion potentials peak negative values subsequent to the half cell test Corrosion rate tests should not be carried out where epoxy coated or galvanized reinforcement is used To conduct this test first mark the bar location and record the bar size and depth The presence of any lap splices should be noted at the test site Second establish an electrical connection to the reinforcement and determine the corrosion potential directly over the bar of interest Note that the electrical connection provided for the corrosion potential survey can be used for this purpose Third use one of the three devices listed below to take readings 1 The 3LP device by KCC Inc USA 2 NSC device by Nippon Steel Corporation Japan 3 Gecor Device by GEOCISA Spain 111 Each device determines the polarization potential of the reinforcing steel Corrosion current is calculated from a simple equation and expressed in terms of milli amperes per square foot of reinforcing steel area mA per sq ft Note that the three devices listed yield different but related results Values obtained by any of the devices may be recalculated into values of another device by using the empirical formulas presented below log I 3LP log I GECOR l
99. e concrete permeability value AASHTO T277 and resistivity value Input the representative water cement ratio and the actual bar cover depth in Equation 6 2 or Figure 6 1 and find the modified t 129 Coated Reinforcing Steel e Epoxy Coated bar e Galvanized bar Estimate the number of years to initiation of concrete deterioration with coated bars and number of years to initiation of concrete deterioration if the bars were not coated Use the same bar cover depth and water cement ratio for both cases Find the difference between the two and add the difference to the number of years obtained from Equation 6 2 or Figure 6 1 and use the result as the modified t 130 7 Evaluation of Performance Chapter 6 established a performance equation relating the concrete condition to the age of the concrete This chapter will assist the user understand deterioration of the concrete by illustrating the equation graphically Use Figure 7 1 to identify the concrete performance curve based on the value of Parameters A and B determined in Chapter 6 For previously repaired rehabilitated and or protected concretes Case 1 Chapter 6 only consider the portion of the curve beyond the concrete age at repair rehabilitation and or protection t As a concrete bridge component ages its condition gradually deteriorates and its condition index increases to a point that some type of treatment must be done As discussed in Chapter 5 the user shoul
100. e defining a new file or copying or editing an existing one The items within this file are as follows e Treatment name the name that you assign to the treatment file when you 238 first define it or subsequently copy it or edit it The name is limited to eight alphanumeric characters and must conform to DOS file naming conventions Typically this name is a brief identification of the type of treatment that is represented As noted earlier treatments that are assigned to different bridges may have the same name CORRODE will still regard them as different files since CORRODE associates each treatment explicitly with the bridge for which it is defined Comment a text field in which you may enter any descriptive information to a maximum length of 64 characters The CORRODE system does not use this information in any way it is strictly for your convenience You may use this field to describe some technical information about the treatment in question for notes on current treatment usage or to identify treatment combinations represented by this file e Technical and cost data the treatment file contains data in four broad categories each associated with a separate data input form that is explained in the sections that follow These data include 1 costs and productivities 2 the estimated nominal life of the repair 3 the effect of the treatment project on traffic flow and 4 adjustment factors e Viewing the data input forms yo
101. e desired selection e g I for TREATMENTS etc 220 Figure 1 Main Menu Options Main Menu Bridges Treatments Analyses Reports Graphs Delete 221 2 3 Quick Tour The main menu allows considerable flexibility in building analyzing and reporting a life cycle cost analysis of different bridge deck treatments for corrosion A typical but by no means the only order in which the main menu items can be accessed is given below You should not feel confined by this example however more general rules on how to proceed through the main menu are given later A typical sequence of main menu selections might proceed as follows e First complete the description of a bridge structure in the BRIDGES block e Second define one or more treatments in the TREATMENTS portion of the menu e Third run a corrosion analysis in the ANALYSES portion of the menu If desired obtain a corrosion related report afterward by calling up the REPORTS menu e Following the corrosion analysis run a life cycle cost analysis of one or more of the treatments that have been defined again in the ANALYSES portion of the menu e View the results of the life cycle cost analyses in graphs on the screen using features provided in the GRAPHS option e The graphs may suggest particular reports that would be most useful to obtain and which may be selected in the REPORTS block e Results needed for future reference may be retained Other fi
102. e has been removed and replaced if any and the only parameter affecting the condition index is the level of chloride contamination Step 3 Use the following equations to calculate Parameters A and B Alternatively use Figures 6 3 and 6 4 to find B and A respectively B In S 100 S S 100 S t tp Equation 6 3 A 100 S S exp Bt Equation 6 4 121 N p pue y 6 1 s sn 6 IS S UAM P 1 6 1 s 2982 6 I lt S uU A IsnorA9Iq pojoajo1g pareriqeysy pasieday JON 21219007 10 910N g 1939uu1eq s juesalg je xopu uorpipuo 93919007 0 0 I S I ey 0t S 0 C 02 ST 01 0 RSHERSERRSESF GRERERESSERSSRESERSSSERRRZRRERS TEEN A FILED AAA uorjgenb4 o uguriojioqd 333919003 ur gd 13 JIMBIVG ururi9 G 0 WBIZOMION C 9 JINZI 122 6 Is UUM I p sn snotA2Jd p2 09 01g Payerlpiqeyoy poseday TON 21219107 104 V 19j9UIEI8q 9JON 0 002 00t 009 008 0001 g Jajomvseg Array P ET UI TT OT 60 0 L0 90 O 0 T0 see INN OZONE AVN aaa l Hh f uonenbq duUeMIOJIIg 3391900D ur V J19 urgied FUIMI9j9q op WBISOUION p o ImJ 123 6 20 Case 2 Concrete not Repaired Rehabilitated and or Protected Previously and without a Special Protection This category applies to all concretes which were not repaired rehabilitated and or protected against corrosion induced deterioration during their service period and were not built wit
103. e of ta in years based on the corrosion data you have provided The life cycle cost analysis discussed in the next section requires a deck deterioration function estimated by the corrosion analysis If you wish to save the deterioration function displayed on the results screen for possible future use press F10 after you have reviewed all of the information on the screen Press Escape to return to the corrosion analysis 5 3 Life Cycle Cost Analysis Note the life cycle cost analysis always applies to the selected bridge i e the bridge whose file name is identified in the information bar at the bottom of the screen If the bridge you wish to study is not currently selected go to the BRIDGES option and select the desired bridge before proceeding with the life cycle cost analysis Refer to Chapter 3 for how to select a bridge Life Cycle Analysis File Selection Once you have entered the life cycle cost submenu CORRODE prompts you for the following information Corrosion analysis file select the name of the corrosion analysis file to be included in the life cycle cost analysis This file selection determines the specific deterioration model to be applied to predict deck distress over time Press Enter when finished e Treatment definition file select the name of the treatment file to be included in the life cycle cost analysis This file selection determines the specific treatment to be applied for which the optimal time and
104. e overlay placement This effect may be included when constructing the after treatment condition index versus time curve depending on the accuracy of the results of life cycle cost analysis To do so consider the following 40 Corrosion Rate Figure 8 Impacts of Various Treatments on Corrosion Rate Q G t Time Case l Rate of Corrosion continues to increase Case 2 Rate of Corrosion levels off Case 3 Rate of Corrosion practically drops to zero Case 4 Rate of Corrosion decreases slowly with time 41 Figure 9 Procedure to Estimate Life of Treated Concrete ive Service Life e SPALL have three times the weight of DELAM in the condition index equation e With a bonded concrete overlay thicker than 1 inch 2 54 centimeters SPALL will form at only about half the rate they would have formed had the overlay not been present DELAM will form at the same rate As an example assume a deck XX years after treatment Assume that without an overlay it has CL 100 DELAM 16 SPALL 4 and a condition index of S 20 With an overlay it would have CL 100 DELAM 16 and SPALL 2 yielding a condition index of S 18 2 Thus the difference is only 1 8 units or 9 percent If the CL was 50 the difference would still be only 1 8 units but the percentage difference would be 13 percent If it is decided that this effect should be included in the prediction of the effective service life after the treatment two approaches ma
105. e purposes only are provided in input forms invoked by these selections 2T Year of repair Table A 7 Corrosion Previous Repair Data Item Spalled area remaining sq ft Delaminated area remaining sq ft Chloride area remaining sq ft Removal cost sq ft 0 0 Default Example Se TS SS SS SET Note data in this menu not required for the example provided 278 Table A 8 Corrosion Present Condition Information Item Default Example Year surveyed 1993 1993 Area spalled sq ft 0 0 Delaminated area sq ft 0 0 Number of rebar chloride values 1 10 Locked in the aggregate N N Benign chloride by weight of 0 00000 concrete Example data for illustrative purposes only are provided in input forms invoked by this selection 279 Table A 9 Corrosion Pre Deterioration Data Item Default PINE Example O Average wet resistivity ohm cm 1000 500 Year of surface chloride survey 1993 1993 Number of surface chloride 1 10 values Mean annual snowfall inches 0 20 Marine environment N N Within 25 ft of seawater N Example data for illustrative purposes only are provided in input forms invoked by this selection 280 Table A 10 Corrosion Post Deterioration Data i M M M a iv Gsa sM s Item Default Example Know when corrosion damage N started If so in what year 1975 Year of surface chloride survey 1993 Number of surface chloride 1 value
106. eatment 12 4 Year 16 Fill out those boxes in Columns 3 and 4 which correspond to the year of next cycle of treatment Year 16 with the maximum tolerable condition index S 35 the condition index after treatment 11 8 and the type of treatment in the next cycle e g patch LSDC Find the approximate concrete condition index for each consecutive year after the treatment from Equation 13 1 Fill out the appropriate boxes of Column 3 with the approximate condition indices determined 13 7 through 32 7 S Rec aie S Index just after Treatment x No of Years after Treatment Effective Service Life after Treatment Index just after Treatment Equation 13 1 Do not repeat treating the concrete if the effective service life of the treated concrete in this example 12 years is more than the remaining years in the consideration period in this example 5 years Step 3 Agency Costs Columns 5 and 6 relate to agency costs Fill out the appropriate boxes of Column 5 with the cost associated with the application of the treatment Chapter 9 187 Fill out the appropriate boxes of Column 6 with the annual cost of monitoring maintaining the treatment Chapter 9 For example in Figures 13 2 13 3 and 13 4 there were no agency maintenance costs Step 4 User Costs Prior to Treatment Column 7 is for user costs prior to the treatment Using the condition index given in Column 3 estimate the user costs prior to the
107. ed Years 31 33 Cathodic Protection 35 Overlay 55 The optimal time for patching occurs strictly in Year 5 although the total cost curve is so flat that the activity would be justified virtually at any time required in the first 10 or 15 years Costs are low of course because the deck is relatively undamaged so the total costs of the treatment are small even though the unit costs per square foot of distressed deck area are relatively high compared to those of the other treatments The optimal time for sealer application occurs strictly in Year 16 although total discounted costs do not vary significantly within 5 years before or after this time Total discounted costs in this region are somewhat more than for concrete patching but still relatively low e Both concrete overlays and cathodic protection have optimal times much later in the deck s life and at higher costs than for either the sealer or patching For overlays the optimal treatment time is 24 years as discussed earlier for cathodic protection it is 26 years These treatments may show greater benefits in future versions of the model as more sophisticated corrosion relationships are included for protection techniques and better data on service life and degree of improvement are developed through other SHRP projects These results indicate the value of preventive and relatively small scale corrective activities at this point of the deck s life cycl
108. ed by assigning the following weights e Spalling is 3 times more important than delamination e Delamination is 2 5 times more important than bar level chloride contamination The condition index is then quantified using Equation 5 1 or Figure 5 1 S CL 2 5 DELAM 7 5 SPALL 8 5 Equation 5 1 and S 100 where S concrete condition index at the time of condition survey and on the basis of condition data expressed as a weighted percentage of the concrete area CL percent of concrete samples with bar level chloride content higher corrosion threshold value In this handbook the corrosion threshold value for conventional concrete is assumed 0 035 percent of concrete weight 1 4 pounds per cubic yard 0 82 kilograms per cubic meter However if aggregates with chlorides locked in them which do not contribute to the corrosion process are used the threshold is 0 035 percent 1 4 pounds per cubic yard 0 82 kilograms per cubic meter plus the amount of benign chlorides Also when a corrosion inhibitor admixture is used in the concrete the threshold is 0 035 percent 1 4 pounds per cubic yard 0 82 kilograms per cubic meter plus the increased chloride threshold due to the inhibitor 113 DELAM percent of concrete area not including spalls that is delaminated SPALL percent of concrete area that is spalled 8 5 a normalizing factor The weighting factors and the normalizing factor used in Equation 5
109. en Rate of Corrosion Levels Off K 0 50 40 VIEN 30 Effective Service Life After 20 WALA A NN 10 AA e to T CN oo ce ma pak oN k oo bo co Years Between Time To First Corrosion and Time to Maximum Tolerable Condition if Concrete Was Not Treated t t 170 Treatment Years ESL 4 12 2 See 1 above for the definition of the parameters in Equation 12 3 The rate of corrosion decreases gradually after the treatment This condition is represented by 1 3 lt K lt 0 typical of concrete overlays Estimate the effective service life of the treated concrete from Equation 12 4 see Figure 12 1 for derivation of the equation or Figure 12 6 ESL t t K t ty t t K Equation 12 4 where K the ratio of the slope of corrosion rate decrease after treatment to the slope of corrosion rate increase before treatment 1 3 K 0 See 1 above for the definition of the other parameters in the Equation 12 4 If K lt tC t t ty then ESL is theoretically infinite This means that the corrosion rate of the treated concrete drops to zero when the condition index is still less than the maximum tolerable condition index S Thus the condition index will theoretically never reach the maximum tolerable The rate of corrosion drops to 0 after the treatment This condition is represented by K infinite in Figure 12 1 typical of cathodic protection
110. ent Equation 13 1 Equation 13 1 assumes a linear relation between condition index and time This approximation is justified since usually after the treatment the slope of the S curve applies However if the exact value of condition index is required Equations 6 1 6 3 and 6 4 may be used Do not repeat treating the concrete if the effective service life of the treated concrete in this example 15 years is more than the remaining years in the consideration period in this example 5 years Treat at t Example in Figure 13 3 Find concrete condition index for each consecutive year starting with the present year t and ending with tm Chapter 6 Fill out the appropriate boxes of Column 3 with the condition indices determined S 15 through S 35 Also fill out the box for S with the index just after the treatment 11 8 use Chapter 11 to decompose S and Chapter 5 to determine the index just after treatment Fill out the box in Column 4 that corresponds to S with the type of treatment patch LSDC Find the effective service life of the treated concrete ESL Chapter 12 10 years Find the year to the next cycle of treatment by adding the effective service life of the treated concrete to the year of treatment 10 8 Year 18 Fill out those boxes in Columns 3 and 4 which correspond to the year of next cycle of treatment Year 18 with the maximum tolerable condition index S 35 the condition index after treatmen
111. ent of concrete weight A constant used in congestion cost formula An exponent used in congestion cost formula PART I METHODOLOGY 1 Overview The deterioration of concrete bridges is a major problem in the operation of the nation s highway system The cost of repairing or replacing deteriorating bridges is one of the most expensive items faced by highway agencies and it is increasing rapidly The main cause of the deterioration is the use of salt in winter maintenance operations The salt penetrates the concrete and corrodes the reinforcing steel eventually resulting in internal cracking and surface spalling of the concrete The deterioration occurs on all concrete bridge components including decks superstructure elements and substructure elements Similar corrosion induced deterioration also occurs on concrete components exposed to marine environments In order to reduce the cost of bridge maintenance at the network level rational actions are required at the project level on the basis of life cycle costs This report discusses a methodology that provides systematic procedures to allow valid life cycle cost comparison of the available options for protecting and rehabilitating specific concrete bridge components These procedures are set forth in the form of both a handbook and a computer program The handbook is contained in Part II of this document the computer program user s manual in Part III Figure 1 summarizes the gene
112. erlay representative water cement ratio The water cement ratio of the concrete surrounding the reinforcing steel and the concrete cover is already known A prorated average water cement ratio will be defined and input in lieu of the answer to Question 1 into the t formula As an example if the total cover per this project s method is 2 75 inches 7 0 centimeters the overlay is 2 0 inches 5 1 centimeters the representative water cement ratio of the overlay is 0 38 and the water cement ratio of the base concrete is 0 45 then the input water cement ratio will be 0 38 2 0 0 45 0 75 2 75 0 40 If more than one protective system is designated such as epoxy coated bar and a latex modified concrete overlay the years of additional life for each will be added to t 22 Present Information Module Flowchart 4 The Present Information Module is next it defines the present condition states of distress The module first asks for information regarding the age of the member being examined The following questions are then asked data entered and the answers used to calculate the present condition index S Question 1 What square footage of the area is spalled to determine SPALL Question 2 What square footage of the area is delaminated to determine DELAM Do not include spalls Question 3 What percentage of concrete samples at reinforcing steel level have chloride content higher than the corrosion thre
113. es a comprehensive condition survey of the concrete surface It determines the extent of corrosion induced spalling as well as the significance of deterioration caused by reasons other than corrosion of the reinforcing steel The output of this procedure for use in the calculations is the percent of the area which has spalls temporary patches covering spalls e g asphalt patches and permanent patches e g concrete patches This methodology cannot be used to determine remedial actions for non corrosion related deterioration e g scaling pop outs surface cracking and wheeltrack wear If 107 Table 4 1 Number of Tests and Samples Methodology Visual Examination Use 5 foot grid on deck 2 5 foot grid on sub and superstructure to locate defects Delamination Survey Use 5 foot grid on deck 2 5 foot grid on sub and superstructure to locate all areas of delamination Distinguish between delaminations and spalls Cover Depth The greater of 1 40 locations per member or 2 N 40 A 5000 locations per member where A area in square feet of member The greater of 1 10 locations per member or 2 N 10 A 5000 locations per member where A area in square feet of member Chloride Profiles Use 5 foot grid on deck 2 5 foot grid on sub and superstructure Additional measurements required to locate sites of anodic highest potential Corrosion Potential Measurements at sites of anodic corr
114. esistivity ASSHTO T277 This test AASHTO T277 determines the relative permeability of the concrete or concrete overlay Also the test may be modified to determine the concrete s wet resistivity A suggested procedure for this purpose is described in Appendix E of Part I of this document Many highway agencies are currently using AASHTO T277 Rapid Determination of the Chloride Permeability of Concrete which requires coring concrete and conducting a laboratory test The permeability is indicated by the electrical charge passed through the concrete The electrical charge is expressed in terms of coulumbs and the concrete electrical resistivity is expressed in terms of ohm cm 288 10 REFERENCES Clear K C Time to Corrosion of Reinforcing Steel in Concrete Slabs Volume 3 Performance after 830 Daily Salt Applications Report no FHWA RD 76 70 Federal Highway Administration U S Department of Transportation Washington DC 1976 Cady P D and R E Weyers Chloride Penetration and the Deterioration of Concrete Bridge Decks Cement Concrete and Aggregates CCAGDP Vol 5 No 2 Winter 1983 pp 81 87 Cady P D and E J Gannon Condition Evaluation of Concrete Bridges Relative to Reinforcement Corrosion Volume 8 Procedure Manual Report no SHRP S 330 Strategic Highway Research Program National Research Council Washington DC 1992 Weyers R E B D Prowell I L Al Quadi M M Sprinkel and M Vorster
115. evice by GEOCISA must be converted on the front end to the equivalent KCC Inc device value 44 Effective Service Life of Concrete with Preventive Treatment Preventive treatment can be initiated prior to significant chloride contamination Preventive treatment extends the effective service life of the concrete by stopping or slowing additional salt intrusion The equal cumulative corrosion procedure is obviously not applicable in these instances since the treatment is applied prior to the time of initiation of corrosion t Therefore a separate procedure has been defined as discussed in Appendix F 45 6 Technical Goal Five Life Cycle Cost Analysis Having determined 1 the concrete performance before treatment 2 the various costs associated with a treatment and 3 the concrete performance after treatment the user must now decide what type of treatment to apply and when to apply it to achieve minimum life cycle cost Technical Goal Five deals with this subject through life cycle cost analysis 6 1 Overview For each feasible treatment alternative the optimal timing of treating the concrete yielding the lowest discounted life cycle cost both agency costs and user costs will be determined The user can then compare treatments on the basis of their recommended times of performance and their predicted minimum life cycle costs in order to select the treatment to be actually used In many cases the recommended activity ma
116. f deterioration as shown below t same as age of the concrete at present t years S condition index at time to first deterioration 1 9 Step 5 Determine the set of data corresponding to the condition index equal to 45 as shown below t age of the concrete at condition index of 45 years as determined from Table 6 1 based on the average wet resistivity of the concrete surrounding the reinforcing steel S condition index of 45 Step 6 Use the following equations to calculate Parameters A and B Alternatively use Figures 6 3 and 6 4 to find B and A respectively B In S 100 Sys S4 100 So ta tas Equation 6 6 A 100 Sys Sys exp Bt s Equation 6 7 125 Step 7 Determine the set of data corresponding to the first signs of deterioration as shown below t age of the concrete at time to first deterioration years Equation 6 2 or Figure 6 1 S condition index at time to first deterioration 1 9 Step 8 Determine the set of data corresponding to the condition index equal to 45 as shown below t age of the concrete at condition index of 45 years determined from Table 6 1 based on the average wet resistivity of the concrete surrounding the reinforcing steel S condition index of 45 Step 9 Use Equations 6 6 and 6 7 or Figures 6 3 and 6 4 to find parameters B and A respectively see Step 6 Step 10 Estimate the surface chloride levels in 10 years b
117. fied by your initials as entered on the title screen e To select the name of the file to be deleted move the cursor to the appropriate name and press Enter CORRODE will prompt you with a message confirming that you indeed wish to delete the file Select Y to proceed with the deletion or N to quit the operation Note Before deleting a bridge file please confirm that the bridge is not the selected bridge identified in the information bar at the bottom of the screen Select another bridge using the Select command described in Chapter 3 before deleting the bridge file in question 270 Appendix Input Data Defaults and Example Values 271 Table A 1 Bridge Input Data Item m Default Example u Bridge Name Default Example Comment No Comment An example of bridge input data for illustration only Year re constructed 1965 1965 Deck area sq ft 100 4 000 Traffic veh day 100 40 000 Normal capacity veh day 100 000 96 000 Average crossing time minutes 1 0 02841 User cost coefficient veh 0 0 00710 User cost exponent 4 0000 4 0000 272 Item Treatment Name Comment Costs and productivity Estimated life and repair Effect on traffic Adjustment factors Table A 2 Treatment Input Data Default Default No Comment Z lt lt x Example Example An example of treatment input data for illustration only Y Y Y Y 273 Table A 3 Treatments Costs and Productivity Data
118. file defined for one bridge to allow you to apply it to another bridge These options are explained in more detail below 4 2 Editing an Existing Treatment File You may edit an existing treatment file at any time to update information complete a description you began earlier or correct previous errors Choose the EDIT TREATMENT option in the submenu CORRODE will display the names of currently defined treatments if any Use the up down cursor keys to scroll through the list until you find the name of the treatment file you wish to edit Select the treatment by pressing Enter You may edit the name of the treatment file as well as other data contained therein Editing the name of the file has the same effect as creating a new file of that name In this case the treatment file bearing the original name will remain unchanged when you complete your work This convention differs from procedures for bridge files in Chapter 3 in which names of current files cannot be changed When your editing changes are completed you may save them by pressing F10 The name of the selected treatment file will appear in the information bar at the bottom of the screen Alternatively you may press Escape at any time to exit the file without saving your most recent changes CORRODE will prompt you to be sure this is your intention Note Treatments are associated with specific bridges in CORRODE since the data in a treatment file depends at least to s
119. first time Two factors affect the effective service life of the concrete after the treatment Those are 1 the inherent corrosion mechanism active at the time of treatment and 2 the treatment s effect on the future corrosion process Generally there are five trends in the corrosion process after the treatment as shown in Figure 12 1 and described below 1 The rate of corrosion continues to increase at the same rate after the treatment This condition is represented by K 1 in Figure 12 1 typical of only patching when deteriorated concrete is removed and replaced but contaminated concrete is left in place Estimate the effective service life of the treated concrete from Equation 12 1 see Figure 12 1 for derivation of the equation note that K 1 or Figure 12 2 163 Figure 12 1 Trends of Corrosion Process After Treatment E ku S N lt v 2 5 ya K 0 K 1 3 1 3 lt K lt 0 p H 8 t t Corrosion Rehabilitation Protection Starts Applied Concrete Age K Ratio of Slope of Corrosion Rate Line After Treatment to Slope of Corrosion Rate Line Before Treatment 164 Fi gure 12 1 Continued Trends of Corrosion Process After Treatment Derivation of Equation of Effective Service Life for Concrete not Repaired Rehabilitated and or Protected Previously Rate of Corrosion Concrete Age Area under rate of corrosion curve from t to t 0 5 C t t Area under rate of corrosion curve from t to
120. g steel The output of this procedure for use in the calculations is the percent of the area which has spalls temporary patches covering spalls e g asphalt patches and permanent patches e g concrete patches 284 This methodology cannot be used to determine remedial actions for non corrosion related deterioration e g scaling pop outs surface cracking and wheeltrack wear If non corrosion related deterioration is significant the most cost effective treatment may be obtained by considering factors which are not covered in this methodology B 2 Delamination Survey ASTM D4580 This test ASTM D4580 is used to survey concrete by sounding the surface to determine the presence of delaminations corrosion induced internal cracks To conduct this test first a grid layout is established on the concrete surface Second the surface is sounded and delaminations noted Third the areas of delamination are marked and mapped for the report Fourth the amount of delamination is computed as a percentage of the surface area Spalls are not included Where rigid overlays are applied ASTM D4580 shall distinguish delaminations from debonding of the overlay Where asphalt concrete overlays are applied delaminations and or debonding should be detected using the procedure recommended by Strategic Highway Research Program Method for Evaluating the Condition of Asphalt Covered Bridge Decks The SHRP test method is documented in Appendix B of SH
121. g this in the above equation yields 2 605 d d AWA P We also know that t time to corrosion can be calculated from t as follows 3 t B t472 1 125 e 9729 For the above data t 32 2 years and t 27 2 years Hence the remaining time to corrosion 27 2 5 22 2 years If the protective system considered has 10 years of life then it can be applied twice before rehabilitation However if the protective system has 20 years of life it can be applied only once before rehabilitation 91 Example 2 5 years 1 4 inches 3 6 centimeters Age at present t Cover 10th percentile value d Representative water cement ratio equivalent to RPT value P 0 45 Surface chloride at present Z 0 20 percent Effectiveness of the protective system 100 percent t 17 8 years and t 13 7 years Hence the remaining time to corrosion 13 7 5 8 7 years Procedure to Determine the Applicability of a Protective System with less than 100 percent Effectiveness In both the examples analyzed above the surface chloride was assumed to remain constant after the protective system as a preventive maintenance was applied But in reality there is always a small seepage of chloride through the protective system depending on the effectiveness of the protective system For example if the protective system is said to be 90 percent effective then it allows only 10 percent of the previous year s increase in surface chlor
122. h a special corrosion protection system at the time of their initial construction Step 1 Determine the set of data corresponding to present as shown below t age of the concrete at present or at time of survey if different years S condition index at present or at time of survey if different Equation 5 1 P If condition index S is greater than 1 9 use Steps 2 and 3 less than or equal to 1 9 but greater than 1 2 use Steps 4 through 6 and less than or equal to 1 2 use Steps 7 through 9 if the surface chloride content Z Equation 6 2 is gt 0 10 percent of concrete weight 4 pounds per cubic yard 2 4 kilograms per cubic meter and use Steps 10 through 13 if the surface chloride content Z Equation 6 2 is lt 0 10 percent of concrete weight 4 pounds per cubic yard 2 4 kilograms per cubic meter Step 2 Determine the set of data corresponding to the first signs of deterioration as shown below t age of the concrete at time to first deterioration years Equation 6 2 or Figure 6 1 S condition index at time to first deterioration 1 9 124 Step 3 Use the following equations to calculate Parameters A and B Alternatively use Figures 6 3 and 6 4 to find B and A respectively B In S 100 S S 100 S ta tp Equation 6 4 A 100 S S exp Bt Equation 6 5 Step 4 Determine the set of data corresponding to the first signs o
123. h the service life of the treatment may consult Wyers et al 34 5 Technical Goal Four Condition Index Versus Time After Treatment This technical goal is similar to Technical Goal One in that two points on the after treatment condition index versus time curve are required for each treatment cycle The first point is immediately after treatment in time but at a lower distress level because the physical distress in most cases is patched The second point is at the maximum tolerable condition index Sn In theory the only way to determine the proper time to perform the second treatment would be to scan all possible combinations of first and second treatments and to determine the life cycle cost for each combination Resulting in a very large number of calculations this method would be impractical especially for the handbook version of this task To avoid this the trial calculations were made and the S point was chosen for all second treatments see Figure 6 5 1 Condition Immediately After Treatment First Point on Curve One must first determine the immediate effect of the treatment on the condition index By its nature the treatment will generally reduce the condition index This is accomplished through repairing delaminations and spalls and removing or neutralize effect of the chlorides This study assumes that all delamination and spalls will always be repaired Thus different treatments vary mainly in their effect on ba
124. he concrete surrounding the reinforcing steel S condition index of 45 Step 3 Use the following equations to calculate Parameters A and B in the performance equation of the treated concrete Alternatively use Figures 6 3 and 6 4 to find B and A respectively B In S4 100 45 S4s 100 Sa ta tas Equation 6 6 A 100 Sys Sys expC Bt Equation 6 7 Step 4 Find the performance curve corresponding to Parameters A and B in Figure 7 1 Enter the performance curve with S equal to S and find t the age of the concrete at the time 176 of the maximum tolerable condition index years The effective service life of the concrete after the treatment is t t in which t is the age of concrete at present years 177 13 Optimum Treatment and Time of Treatment Having determined in previous chapters 1 the concrete performance 2 treatment consideration period 3 compatible treatment alternatives 4 how to determine costs associated with a treatment and 5 the performance after the treatment the user must decide what type of treatment to apply and when to apply it within the treatment consideration period for maximum cost effectiveness This chapter deals with this subject through life cycle cost analysis Briefly this chapter will first determine the optimum time of treatment for each compatible treatment subsequently it will compare the corresponding life cycle costs in order to priori
125. he next cycle of treatment is 10 10 Year 20 Fill out those boxes in Columns 3 and 4 which correspond to Year 20 with S 35 and the type of treatment patch LSDC respectively Find the approximate concrete condition index for each consecutive year after the treatment using Equation 13 1 Satter Treatment S Index just after Treatment x No of Years after Treatment Effective Service Life after Treatment Index Just after Treatment 199 Safer Treatment 35 11 8 x No of Years after Treatment 10 11 8 SanerTreament 2 32 x No of Years after Treatment 11 8 No of Years After S After Treatment Year in Planning Horizon Treatment 1 14 1 11 2 16 4 12 3 18 7 13 4 21 0 14 5 23 3 15 6 25 6 16 7 21 9 17 8 30 2 18 9 32 5 19 10 35 20 Strategy Treat between t and t Use Equation 6 1 or Figure 7 1 to predict the concrete condition index prior to treatment S 100 1 A exp Bt Concrete Age t S Before Treatment Year in Planning Horizon 14 7 1 1 15 8 6 2 16 10 4 3 17 12 6 4 18 15 0 5 19 17 9 6 Fill out the appropriate boxes of Column 3 with the condition indices of S 7 1 through S 17 9 Also fill out the box for S 17 9 with the index just after treatment i e 10 3 Fill out the box in Column 4 that corresponds to S 17 9 with the type of treatment patch LSDC From Part H the effective service life of concrete after treatment ESL is ESL 5 t 5 t
126. her the analysis should begin or 258 CORRODE will display another corrosion menu or input form for you to complete e g the pre deterioration or post deterioration form Distress Index S Note the following brief description helps to explain the results of the corrosion analysis A more complete discussion of the distress index the corrosion analysis and the resulting deterioration function to predict distress over time is given in Part I of this document The corrosion analysis results are expressed in terms of a distress index denoted by S The distress index is a composite index a weighted average of several individual components of distress at a given time Percent of rebar level chloride contamination the percent of deck area in which the rebar level chloride contamination exceeds a threshold value of 0 035 percent of the weight of concrete Percent delamination the percent of deck area that is delaminated excluding spalled areas Percent spalled the percent of deck area that is spalled The weighted averaging formula for the distress index at any time t is as follows S CL 25 DELAM 7 5 SPALL 8 5 for any time t Eq 5 1 where S the distress index expressed as the weighted average percent of deck area that is distressed and CL the percentage of deck area that is chloride contaminated DELAM the percentage of deck area that is delaminated SPALL the percentage of deck area that is
127. here U user costs dollars K 0 1666 per minute per vehicle t duration of repair days q 15 000 vehicles per day t 2 minutes assume detour around the bridge then U 0 1666 2 t 15 000 U 4999 5 t Use the relation above or Figure 10 1 to find U for a given t when tabulating a strategy in Part I below H Prediction of Performance Treated Concrete Chapter 12 Use Case 1 Concrete not Repaired Rehabilitated and or Protected Previously Condition 4 in which the rate of corrosion decreases gradually after the treatment applies to this example Use Equation 12 4 or Figure 12 6 to predict the effective service life ESL after the treatment i e years to condition index of S 35 after the treatment 196 ESL t t K t t C t K Assume K 1 5 ratio of slope of rate of corrosion line after treatment to slope of rate of corrosion line before treatment Since t 7 5 years Part C t 5 years Figure 12 3 and t 23 3 years Part D then ESL I E 5 1 5 233 SY 5 C1 5 ESL 5 t 5 t 5 70 Use the relation above to find ESL for a given t when tabulating a strategy in I below I Optimum Treatment and Time of Treatment Chapter 13 Consider treating the deck with patch LSDC patching and low slump dense concrete overlay contaminated concrete left in place at three different points in time three strategies as show
128. hether corrosion has already begun or will begin in the future e The current deck condition Since the present time is known this procedure determines the present level of distress S from technical information and the results of field surveys that you input in the corrosion menu e The limiting deck condition This procedure determines the time at which the deck will reach the practical maximum level of distress estimated from the technical data you input in the corrosion menu Display of Corrosion Results Results of the completed corrosion analysis are displayed in a special screen containing the following information e Year of construction the year of deck construction or replacement that you entered in BRIDGES e Key points in the distress versus time curve distress index values at two of the three possible points are given These values are based on the present condition of the deck if corrosion has already begun or upon the predicted future trend of corrosion and related distress if the corrosion mechanism has yet to manifest itself The possible points are 1 the time to deterioration t4 2 the present time t and 3 the time to reach the maximum distress tn e Deterioration function expressed as an S shaped curve of the following form S 100 1 A exp Bt This curve is derived from fitting a logistic function to two of the three points discussed above 260 e Time to deterioration the effective valu
129. ide value per year every year once the protective system is set in place Example 3 Age at present t 5 years Cover 10th percentile value d 1 4 inches 3 6 centimeters Representative water cement ratio equivalent to RPT value P 0 28 Surface chloride at present Z 0 15 percent Effectiveness of the protective system 90 percent The surface is protected with 90 percent effective system i e the surface chloride increases by 10 percent every year Z 0 15 percent at 5 years after construction Z at the sixth year after construction 92 0 15 10 15 9 15v5 1 0 10 5 Similarly Z at time to deterioration 0 15 o15 915571 0 10 90 B or in general terms Z yt 1 Z e t t BE Z where e 100 effectiveness in percent 100 Surface chloride in parts per million Z AET eo 9 ao K t Z t Substituting this surface chloride expression in Clear s formula yielded ius 2 695 d d 0 42 0 42 t t e vt vt u Z P l DN MEE t Using the data above t 31 years and t 26 years Hence the remaining time to corrosion 26 5 21 years 93 Example 4 5 years 1 4 inches 3 6 centimeters Age at present t Cover 10th percentile value d Representative water cement ratio equivalent to RPT value P 0 45 Surface chloride at present Z 0 20 percent Effectiveness of the protective system 90 percent Usi
130. iginally or inadvertent deletion of a reports file Delete erases a file All of the commands above work in a similar way 266 When you must select a file name from a list of previously defined files CORRODE will always present the correct list of files to you For example if you are creating a corrosion report CORRODE will identify the list of valid corrosion files For creating the two life cycle cost reports CORRODE will display the valid life cycle cost files The combined life cycle cost report allows you to select a range of files to be included in a report a minimum of one file to a maximum of six All valid life cycle cost files will be displayed for your selection If you wish to display fewer than six files select none for the remaining slots The displayed list of files will always pertain to the selected bridge and the current user id the three initials entered in the title screen see Chapter 2 If you do not find the file name you are looking for check to see that 1 you are currently logged in under the same user id that was used when the file was created and 2 the currently selected bridge is the same as that for which the file was created When you are presented with a list press Enter to select a name from the list press F10 to complete and execute the command or press Escape to cancel the command and return to the REPORTS submenu 6 3 Graphs CORRODE displays graphs of life cycle cost results o
131. ime tat and S 1 9 Calculation One Calculation Two Submodule Submodule Define t at S 1 9 Define t at S 45 e Fit these two points to the distress equation ON Flowchart 2 General Information Module Year Constructed Size of the member in square feet Type of the member Deck Substructure Load deck default file Load Substructure default file Does this substructure have a structural jacket Does this deck have an asphalt concrete overlay yes yes Add cost of jacket removal as Add cost of overlay removal as unit cost of removal multiplied by the area of the jacket unit cost of removal multiplied by the area to be removed Has the member previously been repaired yes no Protect information module Present information module Define the distress equation Repair information module Present information module Flowchart 3 Protect Information Module Water cement ratio of the concrete around the bar yes Is gt Cannot proceed no Input water further Stop yes cement ratio is out of Is p lt 0 2 acceptable range 1 want to input again no 2 don t know no Calculate 10th percentile cover value design cover minus 0 48 in 1 2cm Is data on cove
132. ime t 15 S1eo amp x zg0 0 dx z LOt D 001 S x pul uontpuoo S1vad SUIT PPO 9A031p q Aq xopuy uonrpuo DANSIY 9 durgx sup 104 OF 0 09 0L 08 06 x pul uonipuoo 16 2 Condition index at t S4 15 percent chloride contamination 0 5 percent delamination and 0 percent spalling Therefore S 1 9 We do not calculate the concrete age at the initiation of corrosion t directly Rather the concrete age at the initiation of deterioration t is determined and then t is estimated as follows If t gt 20 years t ta 5 Ift is 10 to 20 years t t 3 5 If t lt 10 years t t 2 It should also be noted that although t is estimated it is for information purposes only in this Technical Goal since it lies too close to t to constitute a separate data point It is however used in Technical Goal Four Condition Index Versus Time After Treatment The age of the concrete at the initiation of deterioration is a required input parameter in all cases except for concrete components which have previously been repaired Concrete age at the initiation of deterioration is defined as the time from construction to the first signs of deterioration in form of rust staining corrosion induced cracking delamination or minor spalling It typically occurs 2 to 5 years after the initiation of chloride salt induced corrosion The calculation of t uses a modified Stratfull f
133. imited because of the bridge s functional features the planning horizon will be the remaining service life of the structure as discussed in Chapter 3 All costs associated with each strategy including the cost of repeated cycles of treatment within the planning horizon are then discounted and totaled for comparison with the other strategies At the end of this economic analysis the user will be able to determine 100 the optimum strategy time of the treatment for a compatible treatment Also the user will be able to prioritize the various compatible treatments based on their life cycle costs A worksheet has been prepared to facilitate life cycle cost analysis 101 3 Service Life Limitation Due to Functional Features If when the current criteria for serviceability are applied the bridge will be functionally obsolete in the near future then the component treatment must be compatible with the remaining life of the structure as a whole Life cycle costs of various strategies can be affected by the remaining service life of the structure as discussed in Chapter 13 Bridge functional features that can limit the remaining service of a bridge include e width clearance e alignment and e load limits The user should estimate the remaining service life of the bridge if the bridge functional features limit the remaining service life to 30 years or less If the exact remaining service life is not known one of the ranges shown bel
134. in Appendix A of Cady and Gannon The test should be conducted at locations of highest corrosion potentials peak negative values subsequent to the half cell test Corrosion rate tests should not be carried out where epoxy coated or galvanized reinforcement is used To conduct this test first mark the bar location and record the bar size and depth The presence of any lap splices should be noted at the test site Second establish an electrical connection to the reinforcement and determine the corrosion potential directly over the bar of interest Note that the electrical connection provided for the corrosion potential survey can be used for this purpose Third use one of the three devices listed below to take readings 1 The 3LP device by KCC Inc U S A 2 NSC device by Nippon Steel Corporation Japan 3 Gecor Drive by GEOCISA Spain Each device determines the polarization potential of the reinforcing steel Corrosion current is calculated from a simple equation and expressed in terms of milli amperes per square foot of reinforcing steel area mA per sq ft Note that the three devices listed yield different but related results Values obtained by any of the device may be recalculated into values of another devices by using the empirical formulas presented below 287 log I 3LP 0 47 0 84 log I NSC log I GECOR 0 47 0 77 log L NSC log I GECOR 0 90 0 92 log I GLP B 8 Permeability of Concrete and Concrete R
135. ion 79 Appendix E Calculation Two Submodule 83 vii Appendix F Criteria for Preventive Maintenance _ tss 89 Part II Handbook Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 Chapter 12 Chapter 13 Chapter 14 InifOGUCtION x eave au ua kuki p Ria Uk k R apup T ate ba Ge SiS 95 Overview of the Handbook eee s a r es 97 Service Life Limitation Due to Functional Features 103 Testing Concrete cv ac Coen SOROR EH 1 oA ee oe ee dodo 105 Condition Determination nns 113 Prediction of Performance leere 117 Evaluation of Performance lees 131 Compatible Treatment Alternatives 000 eee eee 143 Cost Items Associated with Treatment Agency Costs 149 Cost Items Associated with Treatment User Costs 155 Decomposing Concrete Condition Index eese 161 Prediction of Performance Treated Concrete 163 Optimum Treatment and Time of Treatment eese 179 Worked Example uim caw Se RUE hU aene SERRE ERK EERE 191 Part III User Manual for CORRODE Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 viii CORRODE Basics 23 vb oad SR EUROS G RE Ed oa diode ee 211 Getting Started The Main Menu lll eene 219 Bridge Descriptions eee II I
136. is basic rule however you have considerable flexibility in how you organize your analyses You may run several life cycle cost analyses based on a corrosion analysis e g to test different treatments If you receive an error message after a life cycle analysis that suggests going back to the corrosion data you may do so make any corrections needed and then repeat the corrosion analysis and any life cycle cost analyses that depend on it The analyses are selected in the ANALYSES pull down menu Details on how to proceed through each analysis are given in the following sections 5 2 Corrosion Analysis Note the corrosion analysis always applies to the selected bridge i e the bridge identified in the information bar at the bottom of the screen If the bridge you wish to study is not currently selected go to the BRIDGES option and select the desired bridge before proceeding with the corrosion analysis Refer to Chapter 3 for how to select a bridge 247 Figure 4 Analysis Menu Options 248 Corrosion Life Cycle Costs Corrosion Analysis File Selection Corrosion Input Data Analysis Base Year Previous Rehabilitation See Figure 5 Concrete w c Ratio Concrete Cover Data Protective Systems See Figure 5 Survey of Current Present See Figure 5 Life Cycle Analysis Input Data Selection of Corrosion Treatment Files Discount Rate Maximum Level of Distress Results File
137. is equal to 1 9 based on the weighting factors used in Equation 5 1 The concrete age at that time t is estimated from Equation 6 2 unless stated differently in the handbook As an alternative to Equation 6 2 Figure 6 1 may be used to determine t Note that t need not be estimated as discussed if it can be determined from the concrete inspection records t 2 695 d 9 z 9 Py Equation 6 2 where ta age of the concrete at time to first signs of corrosion induced deterioration years d depth of bar cover corresponding to 10th percentile value average depth 1 282 standard deviation inches Z surface chloride concentration from 0 25 to 0 75 inches 0 6 to 1 9 centimeters corresponding to 90th percentile value average 1 282 standard deviation percent of concrete weight t age of the concrete when Z is measured years P concrete water cement ratio Figure 6 2 presents the conceptual flowchart of the overall systematic procedure to determine parameters A and B The following sections detail the procedure in Figure 6 2 and show how to determine the parameters A and B for the three possible cases expected in the field 118 UO0I V1IOIII 9G JO USIC 3s11q 03 our 38 uorje1or193oq jo udis SIT 0 oun Ju IDNO Jo IFY CZ WRM 940197107 Jo MNA aud 4306 3093007 IPLOJJA IENS 9321207 9 919U07 JO Sv ururi9 G 01 WUBIZOWMION I 9 N 119 uonenbg 2ouguuojroq SY ustI
138. itional years protection afforded by this protective system Exit with F10 to save the selection or Escape to ignore it After you have selected all applicable protective systems save the list by pressing F10 and return to the corrosion input data form Pressing Escape will also exit the protective systems list but will cause CORRODE to ignore any of your most recent changes Survey of Present Condition Data from a recent condition survey helps to establish the current condition of the bridge deck and its state of corrosion CORRODE requires that data from a survey be input as part of the corrosion analysis The data are as follows 254 Year surveyed the calendar year in which the survey was performed Area spalled the area of the deck exhibiting spalling in square feet Delaminated area the area of the deck exhibiting delamination in square feet Note this area should not include any of the spalled area input above e Number of rebar chloride values enter the number of chloride samples taken at the level of the reinforcing steel After you enter this number and press Enter CORRODE displays an input sheet in which you enter each chloride sample value in percent of total chlorides by weight of concrete A minimum of 10 rebar level chlorides per 5 000 square feet of deck surface exposed to salty environment whichever is greater is recommended CORRODE will use this information to compute the mean and standard deviation of the
139. ity not available Existing polymer injection repair in concrete Preplaced Patch Aggregate Not Good Not Good 1 Shotcrete may be applied in several stages 148 Shot crete Not Good Not Good Cathod Protect Not Good Not Good Reason Concrete consolidation and bonding can be a problem Mobilization not justified Concrete consolidation can be a problem Certain skills required Cathodic Protection need electricity Insulated bars 9 Cost Items Associated with Treatment Agency Costs Costs associated with various treatments should be known in order to select the most cost effective alternative and determine its timing Costs can vary significantly from one area to another and from time to time depending on many factors The user generally has the most reliable information regarding the cost of a certain treatment in a given Jurisdiction However before the user arrives at any cost for a treatment the standard cost items associated with that treatment must be identified This chapter of the handbook provides standard highway agency cost items associated with each treatment included in the handbook Chapter 8 User cost items are discussed in Chapter 10 The user should determine the cost of each item separately for the treatment considered and then total those itemized costs Users with no previous experience with the cost of the items outlined in this chapter may consult SHRP research
140. ivity of the concrete in the field If CORRODE requires the information needed to estimate the rate of corrosion distress in the future it will display a data input form entitled Pre Deterioration as illustrated in Figure 6 If this form is not displayed you may skip this section Average Wet Resistivity The factors that will affect future corrosion cannot be known completely However an estimate of whether the deterioration rate will be low medium or high should be possible and standard curves can be assigned to each rate designation This estimate can be based on the wet resistivity input as follows 255 Figure 6 Remaining Corrosion Data Corrosion Data Input See Figure 5 CORRODE Analyzes Data Already Input to Answer Question Has Corrosion Already Begun Pre Deterioration Input Post Deterioration Input Estimated Start of Corrosion Surface Chloride Data Average Wet Resistivity Surface Chloride Data 256 Average wet resistivity enter the average wet resistivity of the concrete in ohm cm See Appendix B for the method to determine wet resistivity CORRODE translates this resistivity into a rate of deterioration as follows less than 7 500 ohm cm high between 7 500 and 30 000 ohm cm medium and greater than 30 000 ohm cm is a low rate of deterioration These results are then translated into the estimated time to reach the maximum level of distress defining a
141. l ask which treatment you wish to copy from the bridge identified above CORRODE will display a list of these available treatments through which you may scroll using the up down cursor keys When you locate the treatment to be copied press Enter If you do not see the treatment that you intended to copy you may press Escape to exit this set of submenus and try another approach e g by selecting a different bridge for which to search the list of treatments or by editing an existing treatment or by defining a new treatment e Finally CORRODE will ask you for the name of the file to which the selected treatment is to be copied You may use the same name by which the treatment was known for the previous bridge or you may change this name Press F10 to complete the copying operation or you may press Escape at any time to quit without copying Even if you select the same name as used previously CORRODE will recognize the new file as a different file since CORRODE associates treatment files with the specific bridges for which they are defined For example assume the currently selected bridge has the name CONCRETE You wish to copy a treatment file OVERLAY defined previously for the bridge file named BRIDGE to use with bridge file CONCRETE Using COPY TREATMENT first select the bridge name BRIDGE then the treatment name OVERLAY When CORRODE asks you the name of the file to be copied to you may select OVERLAY or any 237 other valid name
142. l display of input forms These values have been selected so as to be transparent to any analyses that you may run i e they will not interfere with or contradict any of your assumptions These values are null values i e they make no assumptions one way or another and are generally zeros for input variables or assumed values e g for coefficients or exponents in formulas Example files are provided if you wish to see how a problem can be structured These files contain realistic values of input data for a particular problem and can be run directly to see how CORRODE s analyses perform and to inspect its reports and graphs However as with any example these assumed values reflect particular bridge design characteristics materials properties history cost of protective or corrective strategies etc These values are meant to illustrate CORRODE s features not to serve as general values for all bridge decks It remains your responsibility to ensure that the values entered in CORRODE s input forms are realistic for each bridge deck being analyzed To ease the burden of data input for large numbers of bridges you may take advantage of CORRODE s input features to define your own libraries of default values e g for particular classes or designs of bridge decks for particular years of construction or for particular regions in your state These user defined files may then contain appropriate default values that can be tai
143. large data base Resistivity water saturated 73 degrees F is also required when corrosion deterioration has not begun 2 Chloride content 2 Chloride content Procedure given in Reference 3 or AASHTO T260 84 procedure for total chloride Recommends procedure applicable to the field It is given in Appendix F of Volume 8 3 Recommended number of samples 3 Recommended number of samples A specific number of tests and or samples are recommended for all variables used in predicting time to deterioration Both per member and per 5000 square feet requirements 4 Chloride measurements and or profiles Chloride profile data specifically surface chloride and bar level chloride are required irrespective of the hal cell potential values 5 None except for cover 40 per member regardless of size 4 Chloride measurements and or profiles Recommended only when 10 percent or less of half cell potentials are more negative than 0 20 volt CSE 5 Corrosion rate Corrosion rate Required when the chloride content at the bar depth is greater than chloride threshold 0 035 percent and the concrete was repaired rehabilitated previously Recommended only when 90 percent or more of the half cell potentials are more negative than 0 20 volt CSE 6 Half cell potentials 6 Half cell potentials Potential
144. lative corrosion equals that which would have occurred from t time to initiation of corrosion to t time to maximum tolerable condition if concrete was not treated The first step is to construct and extend the before treatment corrosion rate versus time curve The area beneath that curve up to the corrosion rate corresponding to S 37 i e Ca is then calculated That area represents the cumulative corrosion The corrosion rate immediately prior to the initiation of corrosion is known to be 0 Based on field evaluations an assumption can be made that the before treatment corrosion rate versus time curve is a straight line extending upward from 0 at t to the corrosion rate corresponding to S i e Ca and through the present time corrosion rate i e C To calculate the area under the corrosion rate line from t to Cw the following steps should be taken 1 Determine t the age of the concrete at which a condition index of S or index of 36 if selected is expected from the pre treatment index versus time curve of Technical Goal One 2 Calculate the years between time to initiation of corrosion and time to maximum tolerable condition index i e ta to 3 Calculate the yearly rate of increase in corrosion rate by dividing the present corrosion rate C by the years between t age of concrete at present and t 4 Calculate the corrosion rate at the time of maximum allowable condition index C by multiplyi
145. ld be expressed in terms of dollars per square foot of deck area 150 Asphalt Concrete and Waterproofing Membrane Overlays Cost items in this category are as follows e Surface preparation When there is not an existing overlay sandblast the concrete surface When there is an existing overlay this treatment may not be viable since removing the existing overlay will result in a rough surface see Table 8 1 for further information e Placing membrane e Placing asphalt concrete e Traffic control when the bridge is partially open to traffic Cost items in this category should be expressed in terms of dollars per square foot of deck area Sealers and Coatings Cost items in this category are as follows e Surface preparation When there is not an existing overlay sandblast the concrete surface When there is an existing overlay this treatment may not be used since sealers are generally not applied on special concrete overlays or on asphalt concrete surfaces if the existing overlay is removed it will result in a rough surface see Table 8 1 for further information e Applying sealer or coating e Traffic control when the bridge is partially open to traffic Cost items in this category should be expressed in terms of dollars per square foot of deck area 151 Cathodic Protection Slotted System Cost items in this category are as follows e Surface preparation When there is a concrete surface saw cut slots When
146. le 1 Age at present t 5 years Cover 10th percentile value d 1 4 inches 3 6 centimeters Water cement ratio 0 28 Surface chloride at present Z 0 15 percent Effectiveness of the protective system 100 percent Let us assume that this structure is protected from further intrusion of chlorides and hence the surface chloride remains constant at 0 15 percent Though the bar level chloride at present is less than the chloride threshold value the existing surface chloride will diffuse through with time and may eventually increase the bar level chloride to the threshold and beyond Once the bar level chlorides reach the threshold protective systems such as sealers membranes and overlays may not be effective in arresting corrosion Hence it is necessary to determine the time to corrosion when bar level chlorides reach threshold due to 0 15 percent of surface chloride 90 Stratfull developed an equation to determine the time to deterioration for constant surface chloride and was later simplified by Clear The simplified formula by Clear is given below _ 129 di q K pe P where K surface chloride in parts per million d cover in inches 10th percentile value P water cement ratio equivalent to RPT coulombs ta time to deterioration in years first signs of delaminations cracks or rust stains Surface chloride Z as a percent by weight of concrete can be expressed in ppm as K Z 10000 Substitutin
147. le costs and result in the same answer for the optimum treatment and its timing In the computer method life cycle cost for a given treatment is determined for treating concrete in each consecutive year between the present time and the time corresponding to the maximum tolerable condition index This is done for the purpose of life cycle cost comparison to determine the optimum time of treatment For simplicity in the handbook method for a given treatment the user only considers treating the concrete at only three different points in time for the purpose of life cycle cost comparison 1 the present time 2 the time corresponding to maximum tolerable condition index and 3 a time between those two The handbook method of life cycle cost analysis is described in detail in the Users Handbook Part II of this document The computer method of life cycle cost analysis is described in the following section 6 2 Computer Method of Life Cycle Cost Analysis Equations 2 1 through 4 3 provide the technical and economic basis for solving for the optimal timing of the treatment t for each protective or corrective strategy that is selected to be tested This optimal timing of treatment will be the value of t that yields the lowest discounted life cycle cost including both agency costs and user costs for that strategy An optimal time of treatment and its associated minimum life cycle cost will be predicted for each strategy considered The optimi
148. le to the printer CORRODE prompts you for two responses 1 the name of the report file to be printed select one from the list CORRODE provides you and 2 printer instructions You must select a name of the report file from the list presented The second field may be left blank The CORRODE installation procedure loads the SETUP PRN file with commands for an Epson compatible printer This set of commands works reliably with many printers If you have printer formatting problems when trying to print reports try the following 1 Verify that a file SETUP PRN exists in the CORRODE subdirectory If not create an empty file of this name and try printing again 265 2 Copy the current contents of SETUP PRN to a dummy file then erase the contents of SETUP PRN so it is an empty file Essentially you will be invoking your printer s default options 3 If the first or second step does not solve the problem enter an escape command in SETUP PRN that is appropriate to your printer Consult your printer manual for the series of commands required These suggestions are intended only for problems in formatting printed reports If none of these steps solves the problem review the system messages you are receiving to determine whether other causes besides printer communications are preventing you from obtaining a report e g failure to define a reports file a different user id or selected bridge from that used to create a reports file or
149. les may be deleted using the DELETE options This sequence of operations provides a logical order in which to use the features in CORRODE to address a realistic problem In fact it is very typical of how an agency might use CORRODE if it were analyzing a very small number of bridges or looking at bridges one at a time In other cases however more flexibility may be needed e g to input information for several bridges at a time or to describe several treatments at a time Descriptions of bridges or treatments that were entered previously may need to be updated with more recent or more accurate information CORRODE allows the flexibility to approach problems in different ways subject to the following general guidelines e The BRIDGES and the TREATMENTS options may be entered in any order and any number of times Several bridges may be defined first then treatments or vice versa Data entered previously may be edited at any 222 time However a BRIDGE file and a TREATMENT file must be completed before they are used in any of the ANALYSES e To identify which bridge should be studied when specifying a corrosion analysis or a life cycle cost analysis in the ANALYSES option the bridge must be selected Bridge selection is also necessary when defining treatment files Bridge selection is made in the BRIDGES option e The corrosion analysis of a bridge must be completed prior to a life cycle cost analysis of that same bridge in the ANAL
150. locked in the aggregate shown not to contribute to the corrosion process yes Enter benign chloride no Benign chloride 0 0 Chloride threshold 0 035 plus benign chloride locked in the aggregate in percent amp gregate in pe X Adjust chloride threshold if corrosion inhibitor was used Calculate percent chloride beyond threshold limit Calculate percent DELAM and percent SPALL Calculate present condition index as CL 2 5 DELAM 7 5 SPALL 8 5 TIME TO MODULE 63 Flowchart 5 Time to Module Import Data from general present and protect information modules yes no Is S gt 1 9 Post Deterioration Submodule Calculation One Submodule S 1 9 Present condition Pre Deterioration module Time to distress index and yes no Is S lt 1 2 present time t t present time from for corresponding s present module Calculation One Submodule S 1 9 Calculation Two Submodule Fit the two points to the distress equation 64 Flowchart 6 Post Deterioration Submodule Import data from general present and protect information modules Do you know when corrosion induced deterioration was first noticed Input year in which corrosion induced yes distress was first noticed no Year in which surface chloride values t 7 year given were obtained minus the year the structure was built Years to surface chloride buildup year surface chloride samples
151. lored for each individual bridge deck CORRODE is structured to allow flexibility and choice in the analyses you perform The data that are required depend of course on the types of analyses to be performed For example if you wish to perform only a corrosion analysis but not to analyze life cycle costs then only the data related to corrosion would need to be input the data in the life cycle cost menu would not be required at that time Or if you wish to analyze life cycle costs based only on agency costs not bridge user costs then the key inputs for bridge user costs could be specified as zeros Default values and example values for each data input form are included in Appendix A CORRODE Subdirectories and Files The installation procedure sets up a set of subdirectories and files needed to store data define required defaults and manage the file structure With the exception of SETUP PRN already discussed for the printer please do not modify or delete any of CORRODP s file system through DOS errors in system operation will likely result Any changes to files should be accomplished only through the commands and options provided by CORRODE itself as described in Chapters 6 and 7 In addition to the printer files SETUP PRN and RESET PRN already discussed CORRODE also maintains a file BREXT ZZZ in the CORRODE directory This file keeps track of the sequence of bridges already defined and enables CORRODE to know the sequence nu
152. lue as mentioned above e Discounted total costs representing the sum of the agency costs and the user costs The agency cost curve declines over time up to a point because of the effect of the discount rate A higher discount rate would result in a steeper decline over time and a lower discount rate a more gentle decline At about 27 years however agency costs begin to increase albeit in a very flat region of the curve This increase occurs because the area of the deck requiring patching prior to overlay becomes excessive and starts to drive the costs of the treatment higher faster than the discount rate can compensate for the increase Thus the agency cost curve illustrates a tension in the solution between the rate of discount and the rate of deterioration of the bridge deck and the opposing effects of these two parameters on costs Table 2 Input Data for Example Treatments Parameter Concrete Cathodic Overlay Protection Service Life 30 years Cost of Patching dollars per square foot Project Cost to treat entire deck area dollars Time for Project to Treat Entire Deck days Improvement Factor fraction of condition improved 32 Discounted Costs Thousands 160 140 120 100 80 60 40 20 N N Ne h y M prs fe e ne d 12 18 24 30 Figure 10 Optimal Timing of Treatment using concrete overlay as example Time at Which Treatment Is Performed Years Total Cost
153. mber of the next bridge to be defined An unauthorized modification of this number will corrupt CORRODE s ability to manage the list of defined bridges in its files and may result in loss of data and unpredictable errors in operation A series of files is maintained by CORRODE in the PARAM MODEL and REPORT subdirectories within CORRODE These files store several types of data input values that you provide results of CORRODE s analyses formatted reports and tracking information needed for file management No changes to these files should be made through DOS Please use only the commands provided in the CORRODE menu structure to accomplish needed changes in these files 217 2 Getting Started The Mam Menu 2 1 CORRODE Title Screen Short Explanation After the CORRODE system is installed you may start it by typing corrode in the directory in which the system is installed The system will respond by displaying a title screen The screen asks you to enter your initials three maximum These initials will be used to label and manage files containing input data results e g reports graphs logs and other information that is produced by the system Enter your initials and press Enter The system will automatically display the main menu More Advanced Notes The initials that you enter on the title screen when you start CORRODE identify you as a user to the system Your files will be kept separate from those defined by other use
154. ment If your response is Y CORRODE asks you further whether the deck is within 25 feet of seawater to which you again respond either Y or N If your first response on exposure to seawater was N then the second question is suppressed by CORRODE These inputs are applied only if CORRODE determines that the current surface chloride values are extremely low average less than 0 1 percent by weight of concrete because of lack of exposure age and that the estimate of the future time to deterioration t may therefore be incorrect In that 251 case the degree of exposure to seawater will be used with other factors to adjust the estimated value of time to deterioration Analysis After the Onset of Corrosion CORRODE s analysis of the current bridge condition may indicate that corrosion related distress may have already begun To estimate the slope of the deterioration versus time curve CORRODE must have some information about when corrosion related distress began If this information is needed CORRODE will display a data input form entitled Post Deterioration as illustrated in Figure 6 If this form is not displayed you may skip this section Two options are provided to input data on past corrosion depending on whether you already know the year in which corrosion related distress first occurred e Know when corrosion damage started enter Y or N depending on whether you know the year in which corrosion related distress first occ
155. n a recent FHWA study The default value of a 0 15 is based on the premise that the value of travel time itself varies as a function of the length of delay and that for increments of time of less than 5 or 10 minutes difference the value of time decreases to 15 percent or less of nominal value Other values of these constants can be provided for different situations e For situations in which restricted flows may result in delays exceeding 5 to 10 minutes a may be increased to values of 1 0 to 3 0 or more e For situations in which heavy congestion is anticipated involving significant stop and go cycles and attendant delays the parameters o and 8 can be further adjusted to fit curves for congested flow such as those illustrated in reference 9 Please refer to references 9 and 10 for examples of curves illustrating these effects Note also that you input the data used in Eq 4 1 at different times in different files Data related to the bridge itself but independent of treatments are input in BRIDGES e g the deck area and the normal traffic capacity of the bridge e Data dependent on the particular treatment specified as well as on the bridge to which the treatment may be applied are input in TREATMENTS e g the restricted capacity of the bridge and the treatment productivity which may depend upon the type and size of the work zone contemplated Detours If detour was selected earlier you will be prompted for one
156. n below Concrete age t age 14 years year 1992 Concrete age t age 23 3 years year 2001 Concrete age t tm 2 age 18 65 years year 1997 Use Section 13 1 and the worksheet in Figure 13 1 to estimate the life cycle cost of each strategy Results are shown in Figures 14 1 14 2 and 14 3 at the end of this chapter Step 1 Planning Horizon All Strategies From Chapter 3 since the remaining service life of the bridge is 50 years higher than 30 years the planning horizon is 20 years Fill out Column 1 in Figure 13 1 by starting with the year 1992 and ending with the year 2011 Fill out Column 2 by starting with Year 1 and ending with Year 20 Step 2 Condition Index and Treatment Strategy Treat at t Fill out the first row of Column 3 with the condition index at present before treatment S 7 1 and after treatment S 4 7 Fill out the first row of Column 4 with the type of treatment considered patch LSDC 197 From Part H the effective service life of concrete after treatment ESL is ESL 5 t 5 t 5 70 95y where t t 14 years ESL 5 14 5 14 5 703 ESL 28 years Find the year to the next cycle of treatment by adding one to the effective service life of the concrete after treatment 1 28 Year 29 Therefore no further treatment is required during the planning horizon Find the approximate concrete condition index for each consecutive year after the t
157. n points involved in a methodology applicable to various concrete members and state of distress The specifics of each module are presented below General Information Module Flowchart 2 Certain data are required in all instances These data will be obtained in the General Information Module as responses to questions including the following Year Constructed Give the year the concrete was constructed Size of Member in Square Feet For a deck give the top surface area For other members give the overall surface area being analyzed Type of Member Deck or Substructure If a deck is specified the question is asked Does the deck have an asphaltic concrete overlay If the answer is YES such is noted in the output so a cost may be assigned to removal of the overlay during treatment Has the member previously been repaired Answer YES or NO If the answer to the question above is YES proceed to the Repair Information Module and then go to the Present Information Module If the answer is NO proceed to the Protect Information Present Information and Time To Modules Protect Information Module Flowchart 3 This module will ask questions concerning the concrete in the member and the reinforcing steel cover and will ask what if any protective systems were used Findings of a field evaluation are helpful here and are required in the Present Information Module The recommended field evaluation procedure is summarized in Figur
158. n the screen These graphs help you visualize a solution and gauge the sensitivity of the life cycle costs of a treatment to the timing of its application They also provide a quick way to compare different life cycle treatments in terms of their costs versus time The options presented in the submenu correspond to the two types of graphs available e Life cycle cost graph a graphic display of the life cycle cost report for a single treatment discussed in the preceding section The graph displays three cost curves against time in years agency costs user costs and total costs The optimal solution occurs at the point of minimum total cost e Combined life cycle cost graph a graphic display of the combined life cycle cost report discussed in the preceding section The graph displays curves of total costs versus time in years for up to six different life cycle cost analyses This graph is useful to compare different alternatives regarding treatments Working with graphs follows the same conventions as discussed for the life cycle cost analyses and reports since reports and graphs are derived from the same life cycle analysis results files e CORRODE will automatically present the valid list of life cycle cost files from which you may select those to appear in a graph e The combined life cycle cost graph allows you to select a range of files a minimum of one file to a maximum of six All valid life cycle cost files will be displayed for y
159. ncrease of user costs with deteriorating condition of the bridge deck The user cost function for normal bridge conditions i e in the absence of construction work zones or detours is as follows U K S Say Eq 3 1 where U the incremental increase in user costs due to worsening deck condition in dollars per vehicle computed by CORRODE K the unit user cost in dollars per vehicle that you input above S the bridge condition over time that will be estimated by CORRODE in the corrosion and life cycle cost analyses Sa a technological maximum value of distress that you input in the ANALYSIS submenu Chapter 5 n an exponent controlling the growth of user costs with decreasing deck condition This user cost identifies one benefit of keeping a bridge deck in good condition The user cost is intended to reflect primarily travel time considerations and the avoidance of congestion costs that would otherwise be due to badly deteriorated decks However if you wish this function to represent other components of user costs for which you have estimates e g vehicle wear and tear safety related costs there is no reason why you could not include these considerations as well in your determination of the value of the unit user cost k above If reflecting only travel time K should be based on an estimate of the value of travel time for the traffic stream and the uncongested speed or travel time across the bridge 229
160. nd nomograms as alternatives to the equations are presented for this purpose The procedure does not depend on the actual rate of corrosion unless concrete presents certain conditions 2 11 Chapter 13 Optimum Treatment and Time of Treatment Having determined 1 the concrete performance 2 the treatment consideration period 3 compatible treatment alternatives 4 how to determine costs associated with a treatment and 5 the performance after the treatment the user must decide what type of treatment to apply and when to apply it within the treatment consideration period for maximum cost effectiveness Chapter 13 deals with this subject through life cycle cost analysis The user will first determine for each compatible treatment the optimum time of treatment and then will compare the corresponding life cycle costs in order to prioritize those compatible treatments This is discussed below For simplicity for each compatible treatment the user will consider treating the concrete component at three points during the treatment consideration period 1 the present time 2 the time corresponding to the maximum tolerable condition index and 3 some time between those two The economic analysis of the three possible strategies described will be done within a set time frame called the planning horizon The planning horizon begins with the present time and extends for 20 years However if the service life of the component is l
161. nd or protection Concrete condition index predicted for concrete age of t Concrete condition index of 45 Percent of deck area that is distressed at the time of treatment Salvage value present worth Percent of concrete area that is spalled Time since initial construction of concrete age of concrete years Duration of concrete treatment days ta Age of concrete at time to first signs of corrosion induced deterioration years Free flow travel time across the bridge minutes Age of concrete at the time of maximum tolerable concrete condition years Age of concrete at time to first sign of corrosion years Age of concrete at present time years Age of concrete at the time of previous repair rehabilitation and or protection Increment in travel time across the bridge or detour around the bridge caused by construction minutes Age of concrete at the time of planned treatment years Age of concrete at the time of condition index of 45 years Incremental increase in user cost due to worsening deck condition dollars per vehcile User cost during the treatment period dollars User cost due to worsening deck condition dollars per year Mixing water in percent of concrete volume Concrete surface chloride content corresponding to 90th percentile value average chloride content plus 1 282 standard deviation percent of concrete weight Concrete surface chloride content at time to deterioration perc
162. ne as discussed in Item 2 above Figure 9 presents an example for the case in which the corrosion rate is frozen at the before treatment value The effective service life after the treatment can be obtained when Areas A and A are equalized Derivation of the equations for the effective service life after the treatment for various cases as documented in Part II of this report indicated that when Areas A and A are equalized see example in Figure 9 the rate of corrosion is canceled out The effective service life then depends on the ratio of the slope of the after treatment corrosion rate line to the slope of the before treatment corrosion rate line Considering this each candidate treatment will be assigned a default number based on the ratio discussed and the system user will be able to adjust the ratio numbers Special Characteristics of Bare Concretes Treated with Rigid Overlays Concrete treated with overlays has a special characteristic the overlaid structure does not spall as readily as a structure without the overlay When the cover is greatly increased and exceeds about 2 5 to 3 inches 6 3 centimeters to 7 6 centimeters there is a less of tendency for the delamination to break up and for spalls to occur Thus when a bonded concrete overlay or jacket in the case of substructures thicker than 1 inch 2 54 centimeters is added more cumulative corrosion is required for a given condition index to develop than was required befor
163. ng the data above data t 17 years and t 13 years Hence the remaining time to corrosion 13 5 8 years Comments The variable effectiveness formula is slightly more accurate However since all protective systems in consideration should be 90 percent or more effective we believe that procedure 1 assuming 100 percent effectiveness is an adequate approximation Remember however that the life of a preventive maintenance overlay is the time it completely blocks chloride intrusion into the base concrete and not its physical life 94 PART II HANDBOOK 1 Introduction 1 1 Purpose In order to minimize the cost of repairing or replacing of deteriorating concrete bridges at the network level it is essential that cost effective actions be taken at the project level This handbook provides a systematic methodology to guide technical personnel of highway agencies in determining rational cost effective strategies for treating specific concrete bridge components The output from the methodology answers the user s questions regarding the type and timing of treatment to achieve the lowest life cycle cost 1 2 Approach The methodology takes the following factors into account in conducting life cycle cost analysis 1 The condition of the concrete component and its performance 2 The technical compatibility cost and service life of the range of treatment alternatives from which the selection can be made The procedures in
164. ng the result of Item 2 by the result of Item 3 5 Determine the area under the corrosion rate line from t to t in milli amperes per square foot years i e 0 5 Item 2 Item 4 As an example for the case in Figure 7 a condition index of S 36 was projected from the condition versus time curve to occur at 18 9 years Item 1 Corrosion initiation occurred at 4 7 years thus Item 2 is 14 2 years 18 9 yrs 4 7 yrs The field evaluation yielded a corrosion rate of 6 2 milli amperes per square foot 66 7 milli amperes per square meter of bar at 15 years The yearly rate of increase in corrosion rate since initiation Item 3 was 0 602 milli amperes per square foot per year 6 5 milli amperes per square meter per year 6 2 mA sq ft 15 yrs 4 7 yrs The corrosion rate at 5 36 C Item 4 would be 8 55 milli amperes per square foot 92 0 milli amperes per square meter 0 602 mA sq ft yr 14 2 yrs Then the area under the corrosion rate line from t to t is 60 7 milli amperes per square foot years 653 4 milli amperes per square meter years 0 5 14 2 yrs 8 55 mA sq ft Thus the effective service life of any treatment on the example concrete will be the shorter of the following 1 the maximum possible service life of the treatment independent of corrosion 38 o urbs yw gol y bs yur auo savak IUIL o 7 SI 9I pI TI oT SIROA CT S SIEo 6 81 y bs vu c9 m U DS VUI SSS 3 WOI SAIN
165. njection repair in concrete Electricity not available Skid resistance critical Steep grades and or crossfalls Sharp skew and or curvature Bt Conc Over Not Good Not Good Not Good Not Good Not Good for the new membrane e Exceptions can exist AC Seal Cathod Memb Coat Protect Not Not Good Good Not Good Not Not Good Good Not Good Not Good Not Good Not Good When cathodic protection is used with an overlay Unless an existing overlay or a layer of the concrete is removed and replaced When cathodic protection is used with a concrete overlay May be applied on some concrete overlays Rough concrete surface can puncture membranes unless a smooth concrete surface can be provided 7 When slump is 4 5 inches 11 4 centimeters or more Reason Overlays add to dead load Active cracks reflect through concrete Removal of old system results in rough surface Rough concrete surface Scarifying concrete damages anodes Insulated bars Cathodic protection needs electricity Skid resistance may decrease Concrete may flow after strike off Difficult to pave with concrete finishing machines 147 Table 8 2 Selection of Compatible Structural Treatment Alternatives Technical Recast Disadvantage Repair depth more than 2 Inches Small area repair Internal Not vibration Good problem Experienced contractor not available Electric
166. of the following protection done 1 Was a concrete overlay placed 2 Were a membrane and asphalt concrete overlay placed 3 Was a functional cathodic protection installed 4 Was an effective sealer placed The analysis cannot be performed if a cathodic protection systenm has been installed PRESENT INFORMATION MODULE Fit these two points to the distress equation Appendix B Report Format Example 71 Condition Index Yersus Time Before Treatment Sample Computer Run Please enter the current year all four digits 1992 Year the member was constructed all four digits 1977 Size of the member in square feet 4000 372 square meters Type of the member 1 Deck 2 Substructure Input type of member 1 Does this deck have an Asphaltic Concrete Overlay Y N n Has this member been rehabilitated previously Y N n This is Protect Information Module Please enter water cement ratio of the concrete around the bar 0 5 How many cover data are available 40 Please enter cover values in inches 1 1 4 3 6 centimeters 2 1 9 4 8 centimeters 40 0 9 2 3 centimeters Was this structure built with corrosion protective system at the time of construction n 72 This is Present Information Module Please enter the year the member was surveyed 1992 Please enter the total spall area in square feet 240 22 square meters Please enter the total delaminated area in square feet 720 67 square me
167. of the screen Each entry in the main menu corresponds to a major set of CORRODE system operations that are described in later sections of this manual The main menu options are illustrated in Figure 1 and are described below e The BRIDGES option is used to build and edit files containing general information about a bridge and to select a particular bridge deck to be analyzed e The TREATMENTS option is used to build and edit files containing information about a deck treatment e The ANALYSES option is used to invoke two types of analyses in CORRODE 1 the current state of corrosion and corrosion related distress in the bridge deck and 2 a life cycle cost analysis of one or more treatments preventing or correcting corrosion related distress to determine the optimal time and cost of each e The REPORTS option is used to select and display different types of reports available from CORRODE These reports encompass the results of both the corrosion and the life cycle cost analyses e The GRAPHS option is used to display screen graphs of the life cycle cost results e The DELETE option is used to manage files that is to discard bridge treatment corrosion or life cycle cost files that are no longer needed Selections in the main menu may be made by moving the cursor with the left or right arrow keys You may also press the Escape key as many times as necessary to eliminate any pull down menus and then type the first character of th
168. og I GECOR 0 47 0 84 log I NSC 0 47 0 77 log I NSC 0 90 0 92 log I 3LP H Hl I Permeability of Concrete AASHTO T277 and Concrete Resistivity This test AASHTO T277 determines the relative permeability of the concrete or concrete overlay Many highway agencies are currently using AASHTO T277 Rapid Determination of the Chloride Permeability of Concrete which requires coring concrete and conducting a laboratory test The permeability is indicated by the electrical charge passed through the concrete The electrical charge is expressed in terms of coulombs The concrete samples used for AASHTO T277 test may be used to determine the concrete s wet resistivity A suggested procedure for this purpose is described in Appendix E of Part I of this document The concrete resistivity is expressed in terms of ohm centimeters 112 5 Condition Determination The measure of concrete condition is systematically quantified in terms of an index Three factors are used as indicators of deck condition as affected by corrosion Those are spalling delamination and chloride contamination at the bar level Of these when considering repair options at a given time spalling is the most important delamination is the second in importance and chloride contamination at the bar level is the third most important For purposes of this methodology the relative importance of each of these factors indicating the need for repair is express
169. om Equation 12 2 see Figure 12 1 for derivation of the equation or Figure 12 4 ESL t t K t tY t t K Equation 12 2 where K the ratio of the slope of corrosion rate increase after treatment to the slope of corrosion rate increase before treatment 0 lt K lt 1 3 See 1 above for the definition of the other parameters in Equation 12 2 3 The rate of corrosion levels off after the treatment This condition is represented by K 0 in Figure 12 1 typical of asphalt concrete membrane systems sealers and coatings at their best performance or concrete overlays at their worst performance Estimate the effective service life of the treated concrete from Equation 12 3 see Figure 12 1 for derivation of the equation note that K 0 or Figure 12 5 ESL OS t t t t Equation 12 3 167 Figure 12 3 Chart to Find Age of Concrete at Time of First Corrosion 50 40 30 20 10 45 50 Concrete Age at First Deterioration Years t 168 Concrete Age at First Corrosion Years t ISH 1694 u npys dr 191JV YF VAIG AMIJE 1 1 PAAL JON SEM 2501207 JT uonrpuo QBI umnumej oj our pue U01S01102 SILI 0j oum U994J99 SIBA I 4 0 9183 J940 S 3B SISVIIDU UOISOJIO JO 233 U9QA lu unu dl 193 V 3 9V1IDUOD JO IJV IMIS 9A1 29JJT IUIMII JIA 01 WMBIZOMION p z ounZiq 169 Figure 12 5 Nomogram to Determine Effective Service Life of Concrete After Treatment Wh
170. ome degree on the characteristics of the bridge to which it will be applied When you edit a treatment file it will be associated with the currently selected bridge If you wish to edit a treatment associated with a bridge other than the one currently selected in the information bar at the bottom of the screen return to the BRIDGES menu and select the desired bridge before editing the treatment Refer to Chapter 3 on how to select a bridge file 235 43 Defining a New Treatment File You may add to the system s library of treatment files by defining new files In this way you can develop a set of files for relevant treatments to be considered for the inventory of bridge decks in your network To define a new treatment file select the NEW TREATMENT option e CORRODE will respond with a window in which it asks you for a treatment file name In some cases the narne of the previously edited file may already appear e Edit this field to provide the name of the new file and press the F10 key to continue e Normally the name you provide should be different from the names you have defined previously If you enter a name that has already been defined CORRODE will respond with a message asking OK to overwrite existing file If you respond no N CORRODE will return you to the entry field so that you may modify the name you had entered If you respond yes Y CORRODE will display the current contents of the existing file you have specified
171. omputes the estimated area of spalling over time in the life cycle cost analysis Chapter 5 Maintenance cost the average annual cost of maintaining the treatment installation not the bridge deck itself in dollars per square foot This feature is intended to be applied to treatments like cathodic protection which may entail periodic maintenance Estimated Life and Effect of Repair You will use the second TREATMENT data input form to describe the effect of the treatment on bridge condition Specific data inputs are as follows e Effect on chloride delamination or spalls CORRODE provides three Yes No toggle switches by which you indicate the types of distress affected by the treatment If you input Yes Y for one or more of these effects CORRODE will prompt you for additional information in the next group of items If you indicate No N for any item CORRODE assumes that the treatment has no effect on that particular distress component If you indicate No N for all three categories of distress CORRODE interprets this treatment as a preventive activity and will handle it as such in subsequent analyses Note preventive activities can be applied only before the time of initial corrosion at the level of the deck rebar If in the corrosion analysis CORRODE determines that you have specified a preventive treatment and that corrosion has already begun it will display a message informing you of this conflict and suggesting that yo
172. on just after repair b percent delamination just after repair c percent spalls just after repair and d type of protection applied at repair 3 Details of the present condition including percent bar level chloride contamination percent delamination and percent spalls from Present Information Module 26 We know the age of the concrete at the time of the previous repair t From Item No 2 above we can calculate the concrete condition index just after the previous repair S as follows S Item 2 a 2 5 Item 2 b 7 5 Item 2 c 8 5 Eq 2 3 The user also knows the present condition index S and the concrete age at the present time t from the Present Information Module From these data the user can fit the condition index versus concrete age equation An example of this procedure follows Assume a bridge deck was repaired by removal and repair of all delaminations and spalls in 1985 Bar level chloride contamination just after the repair was 75 percent delamination was 0 percent and spalling was 0 percent Thus the condition index just after repair is CL 2 5 DELAM 7 5 SPALL 8 5 75 2 5 0 7 5 0 8 5 S S S 8 8 Since the condition index prior to the repair is not of interest only for the purpose of the plot of index versus time it may be assumed that the age of the concrete at repair t is 0 Presently bar level chloride contamination is 90 percent delamination is
173. oncrete Applying a sealer after patching of deteriorated concrete Applying a concrete overlay over the entire deck after patching deteriorated concrete Installing of a cathodic protection system after patching deteriorated concrete Key values associated with these four options are shown in Table 2 Variations in these methods to reflect different types of patches sealers overlays cathodic protection systems or other types of treatments would be reflected by changing the values of the parameters in Table 2 or other parameters in the model such as the extent of bridge closure Example of Optimal Timing An example of the computation of optimal treatment timing is given in Figure 10 for the concrete overlay Figure 10 shows the life cycle costs attributable to the simulated performance of the overlay treatment in each of Years 1 through 36 of the analysis period Three cost curves are shown Discounted agency costs attributable to performing the treatment plus an amount for the presumed cycle of subsequent repairs computed in lieu of a salvage value as explained earlier 51 e Discounted incremental user costs attributable to 1 riding on a badly deteriorated deck and 2 delays due to congestion during the treatment project These costs are tallied not only surrounding the initial treatment for which the optimal solution is being computed but also for the series of subsequent repairs computed in lieu of a salvage va
174. oot If C is not known use the following procedure to estimate C e Ifa sealer coating an asphalt concrete membrane system or a concrete overlay was previously installed the corrosion rate has almost remained constant In this case assume C C e If none of the above systems was installed assume C is equal to the greater of the following 1 mA sq ft 10 8 mA sq m or C S S in which S concrete condition index just after previous repair rehabilitation and or protection S concrete condition index when C is measured Step 3 Find t age of the previously repaired rehabilitated and or protected concrete at condition index of S maximum tolerable years Chapter 7 assuming no new repair rehabilitation and or protection is applied Then use Equation 12 5 to estimate C the rate of corrosion corresponding to t milli amperes per square foot see Figure 12 7 for derivation of Equation 12 5 C C ta t C t t t t Equation 12 5 173 Rate of Corrosion Figure 12 7 Trend of Corrosion Process After Treatment Concrete Repaired Rehabilitated and or Protected Previously Concrete Age Derivation of Equation for C 174 Ca C AC cates C O ta tp Then C 7 C ta t C t t t t Derivation of Equation for ESL Area under rate of corrosion curve from t to ta 0 5 C C t t Area under rate of corrosion curve from t to t C ES
175. ormula which was originally based on field observations and laboratory tests Input data involve the chloride in the environment the concrete cover and the water cement ratio Modifications to the original formula include those made by Clear in the 1976 Federal Highway Administration Time to Corrosion Volume 3 report and the modification in the current study to input the surface chloride level in lieu of the environmental chloride Appendix D details the formula Although the formula does not consider diffusion coefficients directly Weyers and Cady showed that the results are consistent with a diffusion approach It was chosen for use in lieu of the diffusion approach because 15 years of experience has proven its validity and the diffusion approach is still considered a developing technology In the case of previously repaired concrete S condition index just after repair and t concrete age at the time of repair will replace S and t respectively In the case of concrete which has not reached the stage of visible corrosion induced deterioration the present condition index and age do not provide an appropriate data point Therefore ta which will be in the future when a condition index of S 1 9 is reached is estimated as is t s age of concrete at the time of the index of 45 S 45 Flowchart 1 Appendix A presents the overall technical methodology for achieving Technical Goal 17 One It shows various modules and decisio
176. orrosion inhibitor effect Calculate the percentage of samples greater than or equal to the threshold This will be the percentage of the structure which is chloride contaminated The percentages of spalling and delamination are determined by surveying and mapping the entire surface of the structure Sample Index values for various conditions are given in the following table 77 Appendix D Time to Deterioration 79 Time to Deterioration Stratfull defined the following formula for time to deterioration corrosion induced distress 102 9426 Us 1 22 1011 EE 0 42 371 17 K W where R years to deterioration of concrete exposed to saline water expressed as t in this report C sacks of cement per cubic yard of concrete Si depth of steel below the surface in inches K chloride concentration of water parts per million Wa mixing water in percent of concrete volume Clear 1975 showed that the following modified Stratfull formula yielded similar results 129 d 1 22 R 7 K 0 42 P where depth of bar cover inches surface chloride concentration parts per million water cement ratio time to first signs of corrosion induced deterioration expressed as t in this report DA Il H H idi AUS 80 The above formula applies mainly to sea water situations It can be modified to include all chloride environments If the accumulation of surface chloride is assumed to be proportional to the squa
177. ortar Conventional Mortar Quick Set Hydraulic Mortar Polymer Mortar 8 4 Structural Rehabilitation Protection Concrete Replacement Chloride Contaminated Concrete Removed In this procedure deteriorated and contaminated concrete are removed to the depth required and replaced with concrete e Recasting with Concrete formwork required e Preplacing Dry Aggregate and Grouting formwork required Spraying on Concrete Shotcrete e Patching with Trowel Applied Mortar Conventional Mortar Quick Set Hydraulic Mortar Polymer Mortar Concrete Covers e Spraying on Concrete Shotcrete Concrete Jacketing formwork required 145 Sealers and Coatings e Sealers and Coatings Cathodic Protection e Cathodic Protection 8 5 Compatible Treatments Prior to considering all of the alternatives listed in this chapter for a specific site the user should be aware that restrictions may prevent certain alternatives at that site Tables 8 1 and 8 2 should be consulted for deck treatment and structural treatment respectively to screen out those treatment alternatives which are not compatible with the concrete because of their technical disadvantages 146 Table 8 1 Selection of Compatible Deck Treatment Alternatives Technical Disadvantage Additional dead load critical Active cracks in conc Existing overlay on deck Concrete surface scaled Existing slotted cathod protect Existing polymer i
178. osion potentials limited to the greater of 1 10 locations per member or 2 N 10 A 5000 locations per member where A area in square feet of member Corrosion Rate The greater of 1 2 locations per member or 2 N 2 A 5000 locations per member where A area in square feet of member Concrete Permeability Resistivity e One foot is 0 305 meter e One square foot is 0 093 square meter 108 non corrosion related deterioration is significant the most cost effective treatment may be obtained by considering factors which are not covered in this methodology Delamination Survey ASTM D4580 This test ASTM D4580 is used to survey concrete by sounding the surface to determine the presence of delaminations corrosion induced internal cracks To conduct this test first a grid layout is established on the concrete surface Second the surface is sounded and delaminations noted Third the areas of delamination are marked and mapped for the report Fourth the amount of delamination is computed as a percentage of the surface area Spalls are not included Where rigid overlays are applied the test ASTM D4580 shall distinguish delaminations from debonding of the overlay Where asphalt concrete overlays are applied delaminations and or debonding should be detected using the procedure recommended by SHRP s test method Standard Test Method for Assessing the Condition of Asphalt Covered Bridge Decks Using Pulsed Radar
179. ou anticipate no congestion i e if the treatment requires no work zone or other reduction in the bridge s capacity select congestion and follow the additional instructions below Note that you may investigate different ways of performing treatments e g closing one lane at a time versus closing a few lanes at the same time versus closing the entire bridge These options can be defined as separate treatments analyzed and compared in terms of their relative costs to the agency and to bridge users Congestion If congestion is selected above you will be prompted for the following information relating to the congestion formula described below Unit user cost the cost coefficient K in the formula below expressed in dollars per minute per vehicle This value would be derived from an estimated value of time for the mixed traffic stream on the bridge If no congestion will be caused by the treatment or if you do not choose to compute user costs in your analysis enter zero e Congestion formula coefficient a calibrating constant alpha in the formula below e Congestion formula exponent a calibrating constant beta in the formula below with a value greater than 1 0 e Capacity during project the reduced bridge capacity due to imposition of a work zone expressed in vehicles per day or annual average daily traffic AADT This value should not exceed the normal capacity for this bridge that you input in the
180. ou would like to install CORRODE This may be either a root directory e g CX D or a subdirectory e g C BRIDGES D BRIDGE ANALYSIS The Install Disk will create its own subdirectory named CORRODE within the particular directory that you select e Insert the Install Disk in the a or b drive Change to that drive by typing a or b as appropriate When you receive the A gt or B gt prompt type install You will receive a prompt for the identifying letter of the drive on which CORRODE will be installed the same letter you selected in the first step Enter only the letter identifying the drive e g C D etc and press F10 e CORRODE will automatically load into the hard disk directory that you specify For example if you change to the hard drive directory D BRIDGE ANALYSIS and respond with a D when the installation procedure prompts you for the relevant drive letter the CORRODE system will be installed in the directory D BRIDGE ANALYSIS CORRODE e CORRODE will inform you when the installation is complete You may now start the system by typing corrode and pressing Enter 13 Printer File CORRODE s installation procedure automatically loads a file SETUP PRN in the CORRODE subdirectory This file is used to send formatting instructions i e escape 212 codes controlling line length font size spacing compression etc to the printer This file must exist in the CORRODE subdirectory even if it is an emp
181. our selection If you wish to display fewer than six files select none for the remaining slots e The displayed list of files will always pertain to the selected bridge and the current user id the three initials entered in the title screen see Chapter 2 If you do not find the file name you are looking for check to see that 1 you are currently logged in under the same user id that was used when the file was created and 2 the currently selected bridge is the same as that for which the file was created When you are presented with a list press Enter to select a name from the list press F10 to complete and execute the command or press Escape to cancel the command and return to the GRAPHS submenu There are no file management commands such as file deletion associated with GRAPHS since no permanent files are created The graphs are generated for screen display each time they are needed 267 7 File Management 7 1 Overview CORRODE maintains a system of directories and files to help it do its work Necessary subdirectories are created during the installation procedure all located within the CORRODE directory While these subdirectories and the files therein all follow DOS conventions you should not attempt to use DOS to work with them Many of these files contain not only your data and results but also information that helps CORRODE locate files and link information among files By attempting to access these files through D
182. ow may be chosen to the best of the user s knowledge e 0 5 years e 5 10 years e 10 15 years e 15 20 years e 20 25 years e 25 30 years If a range is chosen then the maximum of that range will be used as the remaining service life in Chapter 13 103 If the remaining service life is estimated at higher than 30 years it may be assumed unlimited for the purpose of life cycle cost analysis in this handbook 104 4 Testing Concrete This chapter guides the user through obtaining site specific test data that are essential to the methodology Tests included in this chapter are discussed in detail in SHRP research by Cady and Gannon and other sources cited in this handbook Those tests investigate concrete element deterioration due to reinforcement corrosion If non corrosion deterioration is identified as significant this handbook may not produce viable results 4 1 Tests Required The tests required and the order in which they are conducted are given in Figure 4 1 First a visual examination of the member is conducted to determine the area of concrete spalling and to determine if other non corrosion related deterioration is present Next the amount of concrete delamination internal concrete cracking caused by bar corrosion is obtained This quantity does not include spalls Third a bar cover depth survey is conducted and bar electrical continuity within the element is determined Fourth concrete chloride content profile
183. parison of the life cycle cost results of several analyses This report tabulates for each year the computed total cost in thousands of dollars for up to six life cycle cost analyses The optimal treatment time is identified by an asterisk for each case These results apply to a single bridge the selected bridge and to multiple treatments or variations in treatments depending on the structure of your analyses The results that are displayed are retrieved from multiple life cycle cost files Refer to the next section to learn how to choose which results will be displayed Report Options When you choose one of the three reports above CORRODE then displays a second submenu from which you select the action you would like to perform For each type of report CORRODE provides the following capabilities Create generates a report from a file for the first time CORRODE prompts you for two file names 1 the name of the file containing the data to be displayed select from the list CORRODE provides you and 2 the name of the file in which the report itself will be stored enter this name in the field provided This name is limited to eight characters and must conform to DOS naming conventions e View displays a report on the screen in tabular form Select one of the report file names listed by CORRODE If no reports have been defined yet for the selected bridge CORRODE will display a message to this effect e Print sends a report fi
184. q8 Ssq pue g V uVe si9 urereq Supe UOTJBIOLII 9q JO USIS JSI JO our oun yuasolg Je uonrpuo Sox AMATISISOY eat 9191900 2 amsodxg ON xopuj uoripuo oum 29 01g qeu2y oum juosoiq Wes JO 2o189 q 1redow ye uorrpuo e uonipuoo ON UOTJeJonojoq Jo UIS ISIL 0 IWILL APO oL onpooo1g jyruop uor ojoiq ends e QUAM IME 9 919UO por jo1Jg poieii mqeuow SA posreday A SnorAa1q sox juouoduro 9301907 uonenb IUC 9 9 19uo2 IUWI 0 JABYIMOLT En d suo2 779 IMI 120 6 1 Case 1 Concrete Repaired Rehabilitated and or Protected Previously This category applies to all concretes which were repaired rehabilitated and or protected against further corrosion induced deterioration during their service period Step 1 Determine the set of data corresponding to present as shown below t age of the concrete at present or at time of survey if different years S condition index at present or at time of survey if different Equation 5 1 Step 2 Determine the set of data corresponding to the treatment as shown below t age of the concrete at repair rehabilitation and or protection years S condition index at repair rehabilitation and or protection Equation 5 1 r Note that the condition index at repair rehabilitation and or protection S relates to the condition just after the treatment Usually at this stage all the deteriorated concret
185. r available yes How many cover data are available Input cover data Calculate average and standard deviation from the input cover values Calculate 10th percentile cover value average cover 1 282 standard deviation no Was this structure built with corrosion protective system at the time of construction yes Please identify number of protective system used from the following list 1 Epoxy coated rebar 2 Latex modified concrete overlay 3 Concrete overlay including low slump dense concrete 4 Full depth Silica Fume concrete 5 Silica Fume concrete overlay 6 Waterproof membrane with asphalt concrete overlay 7 Penetrating sealer 8 Surface protective coating 9 Corrosion inhibitor admixture 10 Cathodic protection 11 Other User inputs additional years of service resulting from each protective system 62 Flowchart 4 Present Information Module Year the member was surveyed Calculate time to present year surveyed year member constructed Enter spalls in square feet Enter delaminations in square feet do not repeat spall area How many bar level chloride values are available generate an array of this size for bar level chlorides Enter bar level chloride data as a percentage of total chlorides by weight of concrete Calculate average and standard deviation of bar level chlorides and 90th percentile value as average 1 282 standard deviation Are there chlorides
186. r level chloride contamination The index can be reduced if all the steel was never chloride contaminated or if the chloride contamination is removed or neutralized The information from Technical Goal Two Decomposing Condition Index can be used to predict the level of chloride contamination at the time of the treatment so that the immediately after treatment condition index can be calculated 35 SUL IF S3IA19S S An59JJ4 juoureor renru JUIWIVIAT JPY PUB 3 10 3g aum SNSIIA uonipuo 9 3m3 x pul uonipuoO 36 5 2 Maximum Tolerable Condition Second Point on Curve The maximum tolerable condition index S is specified based on engineering factors It depends on the structural features of the component as well on as the ride quality of the deck Initially it was decided that the maximum tolerable condition index should not exceed 45 for bridge decks when ride quality is the criterion However considering safety factors and user costs the recommended absolute maximum tolerable index is 80 percent of the index of 45 or an index of 36 i e 0 8 45 36 Note that the maximum tolerable condition index also applies to pre treatment condition Technical Goal One The most important information to determine is the effective service life of the treated concrete the period of time after which the condition index of the treated concrete reaches Sn Effective Service Life After Treatment The time of treatment can affe
187. r the duration of the treatment The degree of congestion is sensitive to traffic volume and the relative reduction in capacity due to the treatment work zone The duration of the treatment is a function of the distressed area and the productivity of the treatment This formula simplifies the actual calculation somewhat since the actual calculation accounts for individual components of distress as well as for overall deck treatments and their respective contributions to overall duration of the treatment The basic idea behind these calculations however is illustrated in the above formula While Eq 4 1 provides a correct conceptual treatment of congestion it is an approximation since it is based on daily rather than hourly traffic estimates Calibration of the constants a and 8 should take this fact into account together with the characteristics of the particular bridge and type of project work zone envisioned e g the number of through lanes lane width and side friction whether one directional or two directional flow is affected and anticipated degree of congestion Literature on the value of drivers time and operational characteristics of highway work zones provides 244 information that can help in these estimates The default values cited above represent the case of restricted but not heavily congested flow through a work zone The default value of 8 4 0000 is based upon regression analyses of curves for such flows developed i
188. rable condition is not necessarily the optimum time to treat the concrete The rest of the methodology is used to determine the type of treatment and its timing to achieve the lowest life cycle cost The methodology presents a range of potential alternatives to treat the concrete and helps the user screen out the alternatives that are not technically compatible with the component The methodology then shows the user how to estimate costs involved in applying each appropriate type of treatment Both agency and user costs can be included Since the methodology applies the life cycle cost concept the performance of concrete after the treatment also needs to be predicted The methodology utilizes the concept of trend in the rate of corrosion after the treatment to predict the performance after the treatment Each potential treatment alternative is represented by a certain trend in the rate of corrosion of reinforcing steel after the treatment The user however has the option of changing the trend in the rate of corrosion that is assigned to a given treatment based on the agency s experience with that particular treatment Unlike the trend in the rate of corrosion the actual rate of corrosion value generally does not play a role in the methodology and it is only needed when certain concrete conditions are present However since historical rate of corrosion data are limited at this time the availability of further rate of corrosion data can support
189. ral approach of the methodology Generally the methodology involves the following objectives Obtain general information on the component and determine the present condition of the component Quantify concrete condition in terms of an index Predict future condition index e Estimate cost of treatment and determine treatment s maximum possible service life on the basis of non corrosion related distress MON Uuon5v 159g Z Sur L Isog 1e UOTOY 1998 T SI IQnS3u uro qo1g AJOS W oz eu NOLLVWYOANI S150 X SOAT T NOLLV YIVAH NO SLOVA eased uonrpuoO pard V SANO LddoOV 10 LAdNI yovorddy pnu 9Jn rq 10 e Predict concrete condition index after treatment Conduct life cycle cost analysis to determine the optimum treatment and its timing To accomplish those objectives the methodology is aimed at the following technical goals 1 1 Technical Goal One Condition Index Versus Time Technical Goal One quantifies the present condition of the concrete in terms of an Index Also it predicts the condition index at any time in the future To do so it supplies two appropriate data points on the plot of condition index versus time so that the concrete performance curve can be determined prior to any treatment The performance curve is determined for all possible cases i e for concrete members which were built with and without protective systems at the time of the initial construction for
190. re 13 1 Step 9 Salvage Value Use the procedure described below to determine the discounted salvage value of the last treatment in the last year of the planning horizon i e the 20th year as shown in the bottom of Figure 13 1 Salvage value applies to the remaining useful life of the treatment beyond the planning horizon and is determined from the following equation SLVG COST RS ESL DF Equation 13 3 where SLVG salvage value present worth dollars COST cost of last treatment sum of all costs in the year of last treatment before discounting dollars RS remaining effective service life of the concrete component after treatment last treatment beyond the planning horizon years ESL estimated effective service life of treated concrete years DF discount factor corresponding to the last year in the planning horizon i e 20th year Step 10 Life Cycle Cost Subtract the discounted salvage value Step 9 from the total present worth Step 8 to find the life cycle cost for the strategy considered Fill out the Life Cycle Cost box in the bottom of Figure 13 1 Step 11 Life Cycle Cost Comparison Compare the life cycle costs of the three strategies i e treat at t treat at ta and treat between t and t and select the strategy with the minimum life cycle cost 190 14 Worked Example The example in this chapter illustrates how the methodology introduced in this handbook is applied to make a
191. re is unusually short because of functional features that will be taken into account later when making a decision on the component treatment This is important since the methodology employs life cycle cost analysis to determine the most cost effective treatment strategy 2 2 Chapter 4 Testing Concrete This chapter provides the user with a guide for obtaining site specific test data that are essential to the methodology The following tests are needed 97 Visual survey and detection of spalls Delamination detection Bar cover depth measurement Chloride content measurement The following tests are only needed when the concrete presents certain conditions e Half cell potentials survey e Rate of corrosion measurement e Permeability resistivity measurement 23 Chapter 5 Condition Determination Chapter 5 deals with determining the condition of concrete The chapter presents a systematic procedure to employ the test data obtained in Chapter 4 to quantify the condition in terms of an index condition index of 100 or lower The test data employed relate to spalling delamination and chloride contamination of the concrete As a concrete bridge component ages its condition gradually changes and its condition index increases to a point where some type of treatment must be done The condition index corresponding to the must condition will be selected by the user on the basis of structural considerations and or the ride quality of
192. re related to increases in travel time caused by traffic congestion on the bridge or by detours around the bridge during bridge closure Nomograms are provided for determining the user costs as an alternative to the equations 2 9 Chapter 11 Decomposing Concrete Condition Index In order to estimate agency costs and user costs associated with a treatment Chapters 9 and 10 the amount of concrete repair removal and replacement of deteriorated and possibly contaminated concrete needs to be predicted at the time of treatment The amount of deterioration and contamination in the future can be predicted by decomposing the future concrete condition index into its component parts i e chloride 99 contamination delamination and spalling This chapter will provide a systematic procedure for decomposing the condition index 2 10 Chapter 12 Prediction of Performance after Treatment The methodology employs life cycle cost analysis to determine cost effectiveness Therefore the service life of the concrete after the treatment also needs to be predicted Generally two factors affect the performance of the concrete after the treatment Those are 1 the inherent corrosion mechanism active at the time of treatment and 2 the treatment s effect on the future corrosion process Chapter 12 uses the concept of trend in the rate of corrosion after treatment to determine the effective service life of the concrete after the treatment Equations a
193. re root of time then Z Z zt or z yt Where Z is the surface chloride as a percentage by weight of concrete at time t during the life of the structure For R years of life 0 5 R gt Z yt Where Z is the surface chloride at time to deterioration R in years K Z x 104 therefore K R x 10 yt Substituting this value of K in Clear s formula 1 129 d or 2 695 d 1921 rz R 0 42 dall rE corn Z 0 5 Z P R x10 P 3 where d depth of bar cover inches P water cement ratio Z surface chloride concentration percent by weight of concrete t age at which Z was measured years This formula will be used to calculate R expressed as t in this report except in special situations 81 Condition index S at time to deterioration t is defined as follows Bar level chloride contamination 15 percent Delamination 0 5 percent Spalling 0 percent Condition index at t S 1 9 Time to Corrosion Initiation t 82 If t gt 20 years t t 5 If t 10 to 20 years t t 3 5 If t lt 10 years t ty 2 Condition index at t S 1 2 10 percent chloride contamination 0 percent delamination and 0 percent spalling Appendix E Calculation Two Submodule 83 Calculation Two Submodule Average Wet Resistivity Years to Condition Index of Distress Rate ohm cm 45 percent percent index increase per year u 10 4 31
194. reatment from Equation 13 1 Sane Treament Sm Index just after Treatment x No of Years after Treatment Effective Service Life after Treatment Index just after treatment Saher Treatment 35 4 7 x No of Years after Treatment 28 4 7 Saner Tramet 1 08 x No of Years after Treatment 4 7 No of Years After S After Treatment Year in Planning Horizon Treatment 1 5 8 2 2 6 9 3 3 7 9 4 4 9 0 5 5 10 1 6 6 11 2 7 7 12 3 8 13 3 9 9 14 4 10 10 15 5 11 11 16 6 12 12 17 7 13 13 18 7 14 14 19 8 15 15 20 9 16 16 22 0 17 17 23 1 18 18 24 1 19 19 25 2 20 198 Strategy Treat at t Use Equation 6 1 or Figure 7 1 to predict the concrete condition index prior to treatment S 100 1 A exp Bt Concrete Age t S Before Treatment Year in Planning Horizon 14 7 1 1 15 8 6 2 16 10 4 3 17 12 6 4 18 15 0 3 19 17 9 6 20 21 2 7 21 24 9 8 22 29 0 9 23 33 5 10 24 38 3 gt S 35 11 Fill out the appropriate boxes of Column 3 with the condition indices of S 7 1 through S 33 5 Also fill out the box for S 33 5 with the index just after treatment i e 11 8 Fill out the box in Column 4 that corresponds to S 33 5 with the type of treatment patch LSDC From Part H the effective service life of concrete after treatment ESL is ESL 5 t 5 t 5 70 where t t 23 3 years ESL 5 23 3 5 23 3 5 70 ESL 10 years The year to t
195. reatment was a sealer coating or asphalt concrete membrane system On the other hand the effective service life may be decreased 25 percent if the new treatment is a sealer coating or asphalt concrete membrane system and the previous treatment was a concrete overlay 12 2 Case 3 Preventive Treatment Case 3 applies to concretes which are not chloride contaminated at the bar level and which will receive protection against further contamination immediately Under this condition the bar level chloride content is equal to or less than the corrosion threshold Although corrosion is not present any existing surface chlorides can diffuse into the 175 concrete later and cause bar corrosion after the treatment Use the following procedure to predict the effective service life of the concrete after preventive treatment Step 1 Determine the set of data corresponding to the first signs of deterioration after the treatment as shown below t age of the concrete at time to first deterioration years Use Equation 12 9 to find t t 2 695 d Z P Equation 12 9 See Equation 6 2 for definition of the parameters in Equation 12 9 S condition Index at time to first deterioration 1 9 Step 2 Determine the set of data corresponding to the condition index equal to 45 after the treatment as shown below ts age of the concrete at condition index of 45 years determined from Table 6 1 based on the average wet resistivity of t
196. remain following the last repair e Removal cost the cost in dollars per square foot of removing a previous repair e g an existing overlay prior to performing a new treatment This unit cost will be multiplied by the deck area and the result will be added to the cost of any treatment If an existing repair need not be removed or if removal incurs no additional cost in performing a treatment enter zero When you have completed your entries on this form exit by pressing F10 to save your work and to move to other items on the corrosion data input form Pressing Escape will also exit the form but will return you to the previous rehabilitation line on the input data form forcing you to reenter the specialized form until you exit with the F10 key Protective Systems If you indicate that a protective system is installed CORRODE displays a list of ten systems from which to make selections You may select more than one Indicate your selections by pressing Enter or Space Bar both of which operate as a toggle switch When an item is selected a small arrowhead pointer appears to the left of the item number on the screen display In some cases additional technical information is requested as noted below The ten systems are as follows 1 Epoxy coated rebar 2 Latex modified concrete overlay 3 Concrete overlay enter the thickness of the concrete overlay in inches and its water cement ratio as a decimal fraction These entries m
197. res Advisory Committee Chairman James J Murphy New York Department of Transportation retired Vice Chairman Howard H Newlon Jr Virginia Transportation Research Council retired Members Charles J Arnold Michigan Department of Transportation Donald E Beuerlein Koss Construction Co Bernard C Brown Iowa Department of Transportation Richard D Gaynor National Aggregates Association National Ready Mixed Concrete Association Robert J Girard Missouri Highway and Transportation Department David L Gress University of New Hampshire Gary Lee Hoffman Pennsylvania Department of Transportation Brian B Hope Queens University Carl E Locke Jr University of Kansas Clellon L Loveall Tennessee Department of Transportation David G Manning Ontario Ministry of Transportation Robert G Packard Portland Cement Association James E Roberts California Department of Transportation John M Scanlon Jr Wiss Janney Elstner Associates Charles F Scholer Purdue University Lawrence L Smith Florida Department of Transportation John R Strada Washington Department of Transportation retired Liaisons Theodore R Ferragut Federal Highway Administration Crawford F Jencks Transportation Research Board Bryant Mather USAE Waterways Experiment Station Thomas J Pasko Jr Federal Highway Administration John L Rice Federal Aviation Administration Suneel Vanikar Federal Highway Administr
198. research by Weyers et al 8 1 Deck Repair Concrete Patches Chloride Contaminated Concrete Left in Place In this procedures deteriorated concrete is removed to the depth required and replaced with concrete e Conventional Concrete Patches Quick Set Hydraulic Concrete Patches e Polymer Concrete Patches 82 Deck Rehabilitation Protection Concrete Patches Chloride Contaminated Concrete Removed In this procedure deteriorated and contaminated concrete are removed to the depth required and replaced with concrete Conventional Concrete Patches Quick Set Hydraulic Concrete Patches e Polymer Concrete Patches 143 Corrosion Inhibitor Application e Corrosion Inhibitor Application Concrete Overlays e Conventional Concrete e Low Slump Dense Concrete e Silica Fume Concrete e Latex Modified Concrete e Polymer Concrete Asphalt Concrete and Waterproofing Membrane Overlays e Preformed Membrane e Applied in Place Membrane Sealers and Coatings e Sealers and Coatings Cathodic Protection e Slotted System without Overlay e Overlaid System 8 3 Structural Repair Concrete Replacement Chloride Contaminated Concrete Left in Place In this procedure deteriorated concrete is removed to the depth required and replaced with concrete 144 e Recasting with Concrete formwork required e Preplacing Dry Aggregate and Grouting formwork required e Spraying on Concrete Shotcrete e Patching with Trowel Applied M
199. rocedure to Determine Type and Timing of Treatment A Test Concrete Chapter 4 The concrete deck was tested in 1992 present year and the following results were obtained Visual Inspection Spalls 1 percent of deck area Patches none e Scaling none e Pop outs none Cracks minor no active cracks e Wheeltrack wear not significant Delamination Survey e Delamination 5 percent of the deck area Cover Depth e Average bar cover depth 1 40 inches e Standard deviation 0 50 inches Reinforcing Steel Electrical Continuity e O K Chloride Profiles Average chlorides at top bars 0 0875 percent of concrete weight or 3 5 pounds per cubic yard e Percent of concrete samples at top bars with chlorides higher than the threshold of 0 035 percent of concrete weight or 1 4 pounds per cubic yard 40 percent average surface chlorides 0 250 percent of concrete weight or 10 pounds per cubic yard standard deviation 0 05 percent of concrete weight or 2 pounds per cubic yard 192 Corrosion Potential Survey e Not conducted Rate of Corrosion Measurements e Not conducted Permeability Resistivity Test Not conducted Overall Evaluation Non corrosion related deterioration is not significant Thus continue using this manual B Condition Determination Chapter 5 Use Equation 5 2 or Figure 5 1 to determine the concrete condition index S CL ZS DELAM 7 5 SPALL 8 5 S 40 2 5 5 7 5 1
200. rrosion model above K is defined as the ratio two slopes in the corrosion rate curve the ratio of the slope after the treatment to the slope before the treatment In some instances CORRODE will set the value of K automatically based on your selection of a model e g for K 0 or K 1 Where a range of K values is implied i e K 0 or 0 K 1 input a value that represents your best estimate of the effect of the treatment on the rate of corrosion e Life with no corrosion if corrosion model 5 is selected above you have indicated that the corrosion rate reduces to zero You must also then input the estimated time in years that the deck will experience no corrosion This feature is intended for use with techniques like cathodic protection If you selected an option other than number 3 above CORRODE does not permit you to enter a value in this field Effect on Traffic Treatments not only affect the condition of the bridge deck their performance may also affect the traffic using the bridge particularly if a work zone is established that restricts capacity or if a detour is necessary This TREATMENT input form requests information that CORRODE will use to assess impacts to users and related increases in user costs due to a treatment project e Traffic impact the type of impact that will result from the treatment depending on how you envision the work will be performed Two options 242 are specified congestion or detour If y
201. rrosion rate at treatment C is equal to the greater of the following 1 milli ampere per square foot 10 8 milli amperes per square meter or C S S where S concrete condition index just after previous treatment 9 gt concrete condition index when C is measured Continue the evaluation as for concretes which were not previously treated Rate of Corrosion Measurement The evaluation presented above includes measuring the corrosion rate C For cases in which the bar level chloride exceeds 0 035 percent by weight of concrete the corrosion rate is determined at anodic most negative half cell potential locations Ten measurement locations per member or per 5 000 square feet 465 square meters whichever is greater are recommended The average and standard deviation are determined and the 90th percentile corrosion rate value is defined as the average plus 1 282 times standard deviation Finally the steel density within the member is examined and rated as high medium or low the 90th percentile corrosion rate value is appropriately adjusted to reflect a value per square foot of member surface See Part IL Chapter 4 SHRP research evaluated three different rate of corrosion devices They yield different but related results This project s examples deal with only one of those devices i e KCC Inc device Thus data obtained using the other two devices i e NCS device by Nippon Steel Corporation and Gecor D
202. rs When you use the system you will be able to list only those files that are assigned to you you will not have access to files created by other users You and other users should therefore observe the following protocols Each user of CORRODE should be identified by a unique set of initials For example if both Mary E Jones and Mike E Jacks will be using the system they should agree on unique identifiers for each e g MJ vs MEJ MJ1 vs MJ2 or any other distinction e g ABC vs XYZ e Different users may define files of the same name CORRODE will still regard these files as separate distinct and independent of each other For example users ABC and XYZ could each define a bridge file named BRIDGE CORRODE will treat these files and all derivative files as separate entities ABC will be able to list edit and use only the BRIDGE file that ABC has created likewise XYZ will be able to list edit and use only the BRIDGE file that XYZ has created 219 Organizations may use this feature to their advantage For example the system of initials does not need to be limited in concept to individual users Different initials could be defined to stand for different organizational units e g different districts or geographic or other breakdowns e g EST could encompass all bridges in the eastern part of a district or state WST the western part etc 2 2 Main Menu The CORRODE main menu is displayed in a bar across the top
203. rticular task at hand Although they vary in appearance they have some common features to help you use CORRODE more effectively 214 e The main menu bar appears at the top of the screen after you have entered the system It provides you access to the different parts of the CORRODE system and organizes system options and capabilities that are available to you Chapter 2 describes the main menu bar in more detail A series of information bars appears at the bottom of the screen identifying current system selections and providing useful reminders Different numbers of bars may appear at different times From the bottom up the information displayed in these bars includes the following 1 Current selections e g the current user id the selected bridge relevant treatment file relevant corrosion file etc Not all of these will appear at the same time 2 Useful function keys general keystrokes to help you with the current operation e g F10 to save or complete a task Escape to quit F6 to clear a field etc Entries in this bar will change with the task at hand 3 Brief instructions a message informing you what needs to be done or input based on the current location of the cursor 4 Status message a message informing you of the current status of the system e g the successful completion of a task This bar will appear only when necessary 1 7 Additional Notes Before Starting Required Data and Default Values C
204. s xample data for illustrative purposes only are provi in input form invo y this selection Note data in this menu not required for the example provided 281 Appendix B Descriptions of Tests 283 APPENDIX B Descriptions of Tests B 1 Visual Examination A visual examination of the concrete surface is used to determine the extent of deterioration and forms the basis for the subsequent concrete condition surveys The visual examination described here is not related to the biennial bridge survey adopted by the Federal Highway Administration The visual examination notes both corrosion and non corrosion related deterioration It should note size location and orientation of 1 Spalls 2 Patches temporary and permanent 3 Scaling 4 Pop outs 5 Cracks 6 Wheeltrack wear These items should be shown on a sketch A grid layout is established on the concrete surface to map concrete deficiencies and to determine their magnitude based on a percent of surface area The severity of the deterioration should be determined quantitatively during a visual examination by measuring the depth of spalls scaling and wheeltrack wear Exposed and corroding reinforcing steel should also be noted The visual examination generates a comprehensive condition survey of the concrete surface It determines the extent of corrosion induced spalling as well as the significance of deterioration caused by reasons other than corrosion of the reinforcin
205. s are obtained The profiles give chloride content at the surface and at the bar level Fifth a half cell corrosion potential survey is conducted to obtain areas of highest potential Sixth rate of corrosion is determined in the areas of highest half cell potential Note that the fifth and sixth activities i e half cell test and rate of corrosion test are generally not required except where concrete was repaired rehabilitated previously however they are performed to support and modify if necessary concepts used in the methodology Also those two activities need not be considered when less than 10 percent of the bar level chloride contents are greater than or equal to the corrosion threshold chloride content Additionally testing concrete for chloride permeability and or resistivity may be required when 1 water cement ratio of the concrete is not known testing the concrete for permeability 2 permeability of a special concrete overlaying the concrete is questionable testing the overlay for permeability and 105 Figure 4 1 Tests Required Visual Examination l Spalling amp Other Defects Delamination Survey 2 Bar Cover Survey amp 3 Bar Continuity Chloride Content 4 Surface amp Bar Level 10 of Bar Level Chlorides Greater Than Corrosion Dss jj Threshold Rate of Corrosion Chloride Permeability Concrete Resistivity When Representative When Corrosion 7 WIC Ratio
206. s of condition data as follows S CL 2 5 DELAM 7 5 SPALL 8 5 Eq 2 1 Appendix C shows in detail how the condition index is calculated As the concrete gradually deteriorates its condition index increases The condition index has a 13 mathematical maximum of 100 and a minimum of 0 although practically speaking it is believed that the condition index should not be allowed to exceed 45 22 Prediction of Future Condition Index Corrosion induced deterioration in concrete is typically represented in the literature as a piecewise linear function as shown in Figure 2a This curve itself is an approximation of how deterioration actually progresses in the field However the three linear segments i e the regime of zero damage prior to corrosion initiation at t the intervening period up to the time to deterioration at t and the growth of damage thereafter cannot conveniently be represented by a single equation The deterioration model Condition Index assumed in this study is therefore shown in Figure 2b This S shaped or logistic curve is a plot of the following equation S 100 1 A exp Bt Eq 2 2 where S concrete condition index predicted for concrete age of t A B parameters controlling the rate of deterioration and the shape of the curve t time since initial construction age of concrete years An example of the condition index versus time curve is shown in Figure 3 The two unknown parameters of
207. s solution specifying the file name that you should use to obtain these results The file name is the same as the results file name you specified earlier in the life cycle analysis menu When you have finished reading this screen press any key to return to the CORRODE life cycle cost submenu If the life cycle cost analysis detects inconsistencies in the bridge corrosion and treatment data that have been specified it will display a message to that effect For example if you have input a preventive treatment but the corrosion analysis shows that corrosion has already started CORRODE will display a message pointing to this contradiction and suggesting that you either check the corrosion data or describe a corrective rather than a preventive treatment 262 6 Viewing Results 6 1 Overview CORRODE provides several ways to view your results of the corrosion and life cycle cost analyses Several types of reports and graphs are provided as described in the following sections These displays and features are available in the REPORTS and the GRAPHS options of the main menu bar respectively as shown in Figure 7 Note reports and graphs are available only for the selected bridge i e the bridge whose file name is displayed in the information bar at the bottom of the screen If you desire reports for a bridge other than the one displayed return to the BRIDGES option to select a new bridge before proceeding with REPORTS or GRAPHS Refer to
208. shold CL A minimum of 10 bar level chlorides per member or per 5 000 square feet 465 square meters of member surface exposed to salt environment whichever is greater is recommended Question 4 Are chloride bearing aggregates involved which have been shown not to contribute chlorides to the corrosion process Answer NO or YES If the answer is YES input the percentage by weight of concrete of benign chloride locked in the aggregate From the answers to Questions 3 and 4 and with corrosion inhibitor information from the Protect Information Module the user calculates the percentage of the bar level chloride values which exceed the total of 0 035 percent by weight of concrete plus the aggregate benign chloride plus the corrosion inhibitor offset Then the present condition index S will be calculated as CL 2 5 DELAM 7 5 SPALL 8 5 corresponding to the age of the concrete at preset t This completes the Present Information Module Then the Time To Module follows Time To Module Flowchart 5 The results of the Present Information Module calculation of S are checked If S is greater than 1 9 it is concluded that t occurred in past and we proceed to the Post Deterioration Submodule If S is less than 1 2 proceed to the Pre Deterioration Submodule If S is between 1 2 and 1 9 t is defined as equal to t and another data point at some time in the future will be defined via the Calculation Two Su
209. sking OK to overwrite existing file If you respond no N CORRODE will return you to the entry field so that you may modify the name you had entered If you respond yes Y CORRODE will display the current contents of the existing file you have specified and the procedure from this point onward will be the same as if you had requested to edit an existing file 3 5 Contents of the Bridge File The contents of a bridge file are the same regardless of whether you are defining a new file or editing an existing one The only difference CORRODE imposes on these two operations is that when defining a file for the first time you specify its name when you are editing an existing file CORRODE displays the assigned name but does not allow you to change it The reason for this feature is that the bridge file name is used as part of the DOS file name for these bridge data as well as for other data files To maintain orderly file management CORRODE retains a bridge file name unchanged once it is assigned The items within the bridge file are as follows e Bridge name the name that you assign to the bridge file when you first define it The name is limited to eight alphanumeric characters and must conform to DOS file naming conventions Typically this name relates to the name of the bridge that is represented e Comment a text field in which you may enter any descriptive information to a maximum length of 64 characters This information is not used
210. sociated with Treatment User Costs Two types of user costs are included in the methodology Those are 1 during treatment costs and 2 prior to treatment costs 10 1 During Treatment Costs Costs during the treatment are related to increases in travel time caused by traffic congestion on the bridge or by a detour around the bridge during bridge closure Use the equation given below or Figure 10 1 to find the user costs resulting from the degree of bridge closure U K t t q Equation 10 1 where U user costs during the treatment period dollars K value of bridge user time while traveling dollars per minute per vehicle t duration of treatment days q average two way daily traffic volume across the bridge vehicles per day increment in travel time across the bridge or in detour around the bridge caused by construction minutes For traveling across the bridge t may be obtained from Equation 10 2 or Figure 10 2 t 0 15 t q CI q OY Equation 10 2 where t free flow travel time across the bridge minutes 155 C1 two way capacity of the bridge during construction vehicles per day C two way capacity of the bridge during normal periods vehicles per day 10 2 Prior to Treatment Costs Decks Only Costs in the period prior to treatment are a function of the condition of the bridge deck and its effect on traffic flow A badly spalled deck would impede traffic flow causing speed
211. square off the removal areas for saw cutting etc Also some new delaminations are created by the removal process or occur during the delay between the survey and contract execution This increase in delamination affects cost Therefore for cost calculations the quantity square feet or percent of delamination should include an increase factor of 1 2 i e 20 percent increase 30 4 Technical Goal Three Cost and Maximum Service Life of Treatment 4 1 Agency Costs Agency costs are those directly associated with the construction of various treatment procedures Agency costs should be known in order to select the most cost effective alternative and determine its timing Construction cost can vary significantly from one area to another and from time to time depending on many factors The user is the most reliable source of information regarding cost of a certain treatment in a given jurisdiction However the user with no previous experience with construction costs may consult SHRP research by Wyers et al and by Bennett et al Four types of costs are included in the methodology as listed below 1 Lump sum costs e g mobilization 2 Fixed costs dependent on fixed member area e g dollar per square foot 3 Variable costs dependent on variable distressed area a dollars per square foot of spalled areas b dollars per square foot of delaminated areas c dollars per square foot of chloride contaminated areas
212. st stream subsequent to the treatment as illustrated in Figure 6 Equation 6 1 is easily solved using numerical methods 49 6 3 Example Solutions of Optimal Deck Treatments How the Solution Works Interpreting of the figures below will be easier with an understanding of the numerical solution a simple procedure For a given treatment the procedure steps through the analysis period year by year Within each year it performs the analysis described below Itsimulates the application of the treatment in that year For example if the treatment is a concrete overlay the computer simulates the performance of the overlay in Year 1 Next it simulates the performance of the overlay in Year 2 It continues this procedure for each succeeding year in the analysis period e Aseach treatment is simulated the procedure tallies all life cycle costs essentially the different terms in Equation 6 1 including both the agency and the user costs prior to the treatment during the project to install the treatment and after the treatment e The various cost components computed above are stored in a table organized by the year in which the selected treatment was simulated to be performed At the end of the analysis i e when costs have been tallied for all years within the analysis period the optimal solution may be obtained by identifying the year with the lowest life cycle costs associated with treatment performance It is very important
213. structure elements Similar corrosion induced deterioration also occurs on concrete components exposed to marine environments In order to reduce the cost of bridge maintenance at the network level it is essential that rational actions are taken at the project level This report provides a systematic methodology to guide technical personnel of highway agencies to rational decisions regarding treatment of specific concrete bridge components The methodology applies the concept of life cycle cost The output from the methodology answers the user s questions regarding the type and timing of treatment to achieve the lowest life cycle cost The methodology is set forth in the form of both a handbook and a computer program The methodology takes the following factors into account to conduct life cycle cost analysis 1 The condition of the concrete component and its performance 2 The technical compatibility cost and service life of the range of treatment alternatives from which the selection can be made The methodology recommends which site specific condition data to obtain and how to use the data to quantify the concrete condition in terms of an index The methodology also provides the user with the performance curve predicting the condition index of the component in the future based on the available condition data From the performance curve the user will determine the time to maximum tolerable condition index The time of maximum tole
214. t 0 5 ESL C C Thus 0 5 C ty t 0 5 ESL C Cy 1 Where C C t t ta t and 2 C C 1 K ESL t t 3 Substituting 2 and 3 in 1 will give K ESL 2 t t ESL tat 0 4 Solving 4 will give ESL as ESL t t K ta t WK 165 Figure 12 2 Nomogram to Determine Effective Service Life of Concrete After Treatment When Rate of Corrosion Continues at the Same Rate K 1 y c gt A IV 1p d G NN INN NON N NN N LS NAN N M k B e Effective Service Life After Treatment Years e Oo t2 e Years Between Time to First Corrosion and Time to Maximum Tolerable Condition if Concrete Was Not Treated t t 166 ESL t t ta t 2 9 t t Equation 12 1 where ESL effective service life years t age of concrete at time of treatment years L age of concrete at condition index of S if the concrete was not treated Chapter 7 years t age of concrete at time to first sign of corrosion years Find ta time to first sign of deterioration from Chapter 6 Enter Figure 12 3 with t and determine t 2 The rate of corrosion increases gradually after the treatment but at a slower rate This condition is represented by 0 K 1 3 in Figure 12 1 typical of sealers coatings and asphalt concrete membrane systems Estimate the effective service life of the treated concrete fr
215. t 11 8 and the type of treatment in the next cycle patch LSDC Find the approximate concrete condition index for each consecutive year after the treatment from Equation 13 1 Fill out the appropriate boxes of Column 3 with the approximate condition indices determined 14 1 through 32 5 S rk Ea S Index just after Treatment x No of Years after Treatment Effective Service Life after Treatment Index just after Treatment Equation 13 1 Do not repeat treating the concrete if the effective service life of the treated concrete in this example 10 years is more than the remaining years in the consideration period in this example 3 years 3 Treat between t and t Example in Figure 13 4 Find the concrete condition index for each consecutive year starting with the present year t and ending with t t 2 Chapter 6 Fill out the appropriate boxes of Column 3 with the condition indices determined S 15 through Spm 24 Also fill out the box for S with the index just after the treatment 11 8 use Chapter 11 to decompose S and Chapter 5 to determine the index just after treatment Fill out the box in Column 4 that corresponds to Spm with the type of treatment patch LSDC Find the effective service life of the treated concrete 12 years use Chapter 12 to determine the ESL Find the year to the next cycle of treatment by adding the effective service life of the treated concrete to the year of tr
216. ternatives Chapter 8 Use Table 8 1 to screen out the incompatible treatment alternatives The rest of this example will only consider one alternative patching and low slump dense concrete overlay in order to determine its optimum timing for maximum cost effectiveness The same procedure can be used to determine the timing and life cycle costs of each compatible alternative for comparison F Cost Items Associated with Treatment Agency Costs Chapter 9 e Removing patching deteriorated concrete 35 per square foot of deteriorated concrete e Scarifying deck 0 75 per square foot of deck e Placing and curing 1 5 in LSDC overlay 2 85 per square foot of deck e Traffic control 2 00 per square foot of deck area G Cost Items Associated with Treatment User Costs Chapter 10 Prior to Treatment Costs Use Equation 10 2 or Figure 10 3 U K S S 365 qj where U user costs dollars per year Sa 35 q 15 000 vehicles per day K a t K Assume t 0 06 minutes free flow travel time across 300 ft bridge 195 K 0 1666 per minute per vehicle and a 50 50 percent reduction in travel time This will give K 0 50 x 0 06 x 0 1666 0 005 per vehicle then U 0 005 S 35 365 x 15 000 U 27 375 S 35 Use the relation above or Figure 10 3 to find U for a given S when tabulating a strategy in I below During Treatment Costs Use Equation 10 2 or Figure 10 1 U K t t qo w
217. ters How many bar level chloride values are available 10 Please enter chloride values as percent by weight of concrete 1 0 0230 2 9 0 0179 10 0 1229 Are there chlorides locked in the aggregate shown not to contribute to the corrosion process Y N n This is Time To Module This is Post Deterioration Submodule Do you know when i e at what year corrosion induced deterioration was first noticed n Please enter the year the surface chloride values were obtained 1992 How many surface chloride values are available 10 Please enter surface chloride values as percent by weight of concrete 1 2 03423 2 03678 10 04115 The Condition Parameters are Condition Index at Time to First Deterioration S 19 Concrete Age at First Deterioration t 6 7 years Condition Index at Present S 20 73 Present Age of the Concrete t 15 years Deck Area 4000 square feet 372 square meters Constants of the Distress equation are Al 407 2 B1 0 3082 Condition Index by Predictive Model Q 5 g g Q Time years For this example Condition Index S 100 1 407 2 exp 0 3082 x years Note No protective system used Not previously rehabilitated Constructed in 1977 Field evaluated in 1992 Water Cement Ratio 0 5 Spalls 6 Surface Chloride 90th Percentile Value 0 4247 Delaminations 18 Cover over bar 10th Percentile Value 0 774 in Deck Area Contaminated
218. th of the steel are greater than the corrosion threshold chloride content The procedure for administering this test follows 1 Establish a grid on the concrete surface 2 Provide an electrical connection to the steel ground 3 Place a half cell corrosion detection device on the concrete surface at the grid points 286 4 Record the electrical potential readings Note that the test cannot be conducted in the absence of the electrical continuity of the reinforcing steel This procedure obtains the location of highest half cell potentials peak negative potentials for the subsequent rate of corrosion testing The location of highest potentials can be obtained in the field by scanning the concrete surface around the anodic areas with a half cell device The locations of anodic areas are obtained by plotting the grid half cell potentials and drawing equipotential contour lines The corrosion potential survey is not recommended for epoxy coated or galvanized rein forcement This is because epoxy coated bars are electrically insulated from each other and readings on galvanized bars indicate the potential of the zinc coating Also the test cannot be conducted where concrete is overlaid with a dielectric material such as a membrane polymer material or asphalt unless the asphalt is saturated B 7 Rate of Corrosion Measurement The SHRP Standard Test Method for Measuring Instantaneous Corrosion Rate of Reinforcing Steel is documented
219. the EDIT BRIDGE option e CORRODE will display a blank window You cannot enter anything in this window This feature is to remind you that only the selected bridge can be edited Press F10 to continue editing or Escape to quit for example if you need to select a different bridge e If you pressed F10 above CORRODE will display the current contents of the selected bridge file which you may then proceed to edit Explanations of these data are presented later in this chapter e When your editing changes are completed you may save them by pressing F10 Alternatively you may press Escape at any time to exit the file without saving your most recent changes CORRODE will prompt you to be sure this is your intention 3 4 Defining a New Bridge File You may add to the system s library of bridge files by defining new files In this way you can develop a set of files for all reinforced concrete bridge decks in your network that you may wish to analyze To define a new bridge file select the NEW BRIDGE option e CORRODE will respond with a window in which it asks you for a bridge file name In some cases the name of the previously edited file may already appear e Edit this field to provide the name of the new file and press F10 to continue 22 e Normally the name you provide should be different from the names you have defined previously If ycu enter a name that has already been defined CORRODE will respond with a message a
220. the rate of corrosion trends assigned to various treatments in the methodology Therefore agencies are encouraged to collect pre and post treatment rate of corrosion data from selected sites To conduct life cycle cost analysis the user of the methodology will first select a type of treatment from the range of compatible treatment alternatives available The user will then consider treating the concrete component at different points in time for life cycle cost comparison Those different points in time are bounded by 1 the present time 2 the time of maximum tolerable condition The economic analysis of each of the strategies considered is done systematically All costs associated with each strategy including costs of repeated cycles of treatment agency and user costs are then input into the system The output from the system is the life cycle cost of each strategy The lowest life cycle cost represents the optimum strategy i e optimum time of treatment for the type of treatment selected Once the optimum time of treatment and life cycle cost for one treatment is determined the user will employ the same procedure to determine the optimum time of treatment and life cycle cost for other treatments At the end the user will be able to prioritize the various types of treatments based on their life cycle costs The most cost effective treatment will be the one with the lowest life cycle cost and it should be applied at its optimum time C1
221. there is an existing di electric overlay e g asphalt concrete membrane or polymer concrete this treatment is not recommended since removing the existing overlay will result in a rough surface e Placing wire anodes in slots Placing electrically conductive polymer in slots Traffic control when the bridge is partially open to traffic Cost items in this category should be expressed in terms of dollars per square foot of deck area Cathodic Protection Overlaid System Cost items in this category are as follows e Surface preparation When there is not an existing overlay Scarify the concrete surface When there is an existing overlay remove the existing overlay e Attaching of mesh anodes to the surface e Placing and curing concrete overlay e Traffic control when the bridge is partially open to traffic Cost items in this category should be expressed in terms of dollars per square foot of deck area 152 9 2 Cost Items Associated with Applying Structural Treatments Concrete Replacement Cost items in this category are as follows e Removing contaminated and or deteriorated concrete e Formwork formwork is not required for shotcrete and patching e Placing and curing concrete e Traffic control when the bridge is partially open to traffic Cost items in this category should be expressed in terms of dollars per cubic yard of replacement or dollars per square foot of replacement if the depth of the patch is taken in
222. thickness of the overlay and the bar cover depth excluding the overlay Input the weighted average water cement ratio and the total bar cover depth including the overlay in Equation 6 2 or Figure 6 1 and find the modified t Weighted Average W C Ratio Overlay Representative W C Ratio from Concrete Permeability AASHTO 1277 x Overlay Thickness Total Cover Overlay Thickness x Base Concrete W C Ratio Total Cover Equation 6 8 Membranes Sealers Coatings e Membrane with Asphalt Concrete Overlay e Penetrating Sealer e Surface Coating Determine the number of years the protective system will block the chlorides from penetrating the concrete effective service life of the protective system and add it to the number of years found from Equation 6 2 or Figure 6 1 use the result as the modified ta The effectiveness of membrane and sealer protective system may be checked by test methods described in Cady and Gannon Concrete Admixtures e Concrete with Corrosion Inhibitor e Concrete with Silica Fume For corrosion inhibitors determine the number of years the protective system will delay initiation of the corrosion induced deterioration based on the amount of inhibitor added to the concrete mix Add the number of years found to the number of years obtained from Equation 6 2 or Figure 6 1 use the result as the modified ty For concrete with silica fume admixture determine a representative water cement ratio from th
223. tive service life of treated concrete The total discounted life cycle cost to be minimized for a given treatment strategy The ratio of the slope of corrosion rate line after treatment to the slope of corrosion rate line before treatment Chloride concentration of water parts per million Value of bridge user time while traveling dollars per minute per vehicle A calibrating constant for user cost prior to treatment dollars per vehicle The life of each treatment following the initial treatment Periodic maintenance cost only cathodic protection A fixed time as for mobilization Number of each consecutive year in planning horizon An exponent controlling the growth of user cost with deteriorating deck condition RS A constant representing the ratio of delaminated concrete areas to spalled concrete areas in a typical case Concrete water cement ratio Productivity of treatment square feet per day Average two way daily traffic volume across the bridge vehicles per day Discount factor for optimization procedure Age of concrete at time to first sign of corrosion induced deterioration original version of t Remaining effective service life of treated concrete beyond the planning horizon Concrete condition index Depth of steel below concrete surface Maximum tolerable concrete condition index Concrete condition index at present Concrete condition index at time of previous repair rehabilitation a
224. tize the compatible treatments These procedures are discussed below For simplicity for a compatible treatment the user of the handbook will consider treating the concrete at only three different points in time for comparison 1 Present time Concrete Age t Index S 2 Time corresponding to maximum tolerable condition index Concrete Age ta Index Sp 3 Time between t and t Concrete Age t t 2 Index Spm For the purpose of life cycle cost comparison only the user may also assume concrete treated at a point in time in the past and use the same procedure outlined in this chapter to determine the corresponding life cycle cost In this handbook the economic analysis of the three possible strategies described above will be done within a set time frame called the planning horizon The planning horizon begins with the present time and extends for 20 years However if the service life of the component considered for treatment is limited due to the functional features of the bridge the planning horizon will be the remaining service life of the structure see Chapter 3 for details For simplicity this methodology assumes that after the initial treatment the concrete will only be treated when its condition index has reached S maximum tolerable This assumption is justified for two reasons 1 when costs are discounted the timing of the 179 costs that occur far in the future do not significantly affect the
225. tne 225 Description of Treatments eee ee n n 231 ILI OBERE T EE TEE p a SLLISLIIIIL IL 101 Q d 247 Chapter 6 Viewing Results _ 263 Chapter 7 File Management 269 Appendix A Input Data Defaults and Example Values 271 Appendix B Descriptions of Tests _ 283 References 289 Part I Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 List of Figures Page General Approdo 2 5 uox c smash qu phaea ae 10 Bridge Deck Deterioration Model 15 Condition Index by Predictive Model 16 Evaluation of Field Structures y J vz uy l y u Rr REA eR vn 19 Sample Condition Index Curve for a Previously Repaued SUUCHIIG sch eerste seek p PER d Rs 28 Condition Versus Time Before and After Treatment 36 Corrosion Rate Versus IM 24 o2 og aquo abe ce Bacar 39 Impacts of Various Treatments on Corrosion Rate 41 Procedure to Estimate Life of Treated Concrete When Corrosion Rate is Held Constant u yayapa is esp S EE dee RS ges 42 Optimal Timing of Treatment using concrete overlay as example a score ae dde Xa eto dor SO wre es wasu ew Ee ee 53 Comparison of Treatments 2 22229 9p E RR 55 Difference of Traffic using overlay as example
226. to consideration Concrete Covers Cost items in this category are as follows Surface preparation sandblasting e Formwork form work is not required for shotcrete e Placing and curing concrete e Traffic control when the bridge is partially open to traffic Cost items in this category should be expressed in terms of dollars per square feet of concrete area treated Sealers and Coatings Cost items in this category are as follows e Surface preparation sandblasting e Applying sealer or coating e Traffic control when bridge is partially open to traffic 153 Cost items in this category should be expressed in terms of dollars per square foot of concrete area treated Cathodic Protection Cost items in this category are as follows e Surface preparation sandblasting e Attaching mesh anodes to the surface e Placing and curing protective mortar shotcrete e Traffic control when the bridge is partially open to traffic Cost items in this category should be expressed in terms of dollars per square foot of concrete area treated 9 3 Cost Item Associated with Monitoring and Maintaining Treatment Certain treatments may require periodic costs of monitoring and or maintaining the treatment For example cathodic protection installations need to be periodically monitored for the polarized steel potentials regardless of the age of the system to maintain the potentials within the prescribed limits 154 10 Cost Items As
227. to note that the time dimension is correlated with the condition of the bridge deck Treatments that occur at the beginning of the analysis will affect the deck in its current condition Treatments later in the analysis will affect a deck as it has deteriorated from its current condition to its condition at that later point in time Example Data For this example we assumed the following as constant for all the treatments A relatively new lightly distressed bridge deck with an area of 4 000 square feet 372 square meters four lanes wide totaling 48 feet 15 meters with a length of about 83 feet 25 meters e An average daily traffic volume of 25 000 with a value of time of 10 per hour 50 A free flow crossing time of 0 01894 minutes based on the bridge length of 83 feet 25 meters and a speed of 50 miles per hour 80 kilometers per hour A normal two way capacity of 96 000 vehicles per day and a capacity during the treatment of 57 600 vehicles per day assuming one lane of the bridge is closed at a time No annual maintenance either of the bridge deck before the treatment or of any of the treatments after their installation A discount rate of 5 percent The factors that varied in each of the cases were the characteristics of the treatments Four basic types of protective or corrective strategies were considered in these examples Patching i e patching with portland cement concrete after removing deteriorated c
228. ts in the larger number Surface chloride samples must not be taken in patched areas Upon receipt of these data t is calculated as the Year Data Taken minus Year Concrete Built and t is calculated from the formula presented in Appendix D and adjusted per the first item above Pre Deterioration Submodule Flowchart 8 When considered t in the future the same input items are requested or obtained from the other modules as for the Post Deterioration Submodule However if the surface chloride values are extremely low because of lack of exposure age the calculation of t will be incorrect Therefore the surface chlorides are checked after they are entered If 24 the average is greater than or equal to 0 10 percent of chloride by weight of concrete proceed as per the Post Deterioration and Calculation One Submodules If the average is less than 0 10 percent proceed to the Adjust Submodule as follows When the surface chlorides are quite low the user needs an estimate of surface chloride values in 10 years To aid in this estimate input the mean annual snowfall in inches in the vicinity of the structure and then answer the subsequent questions as well Is the concrete exposed to a marine environment YES or NO If the answer to the marine environment question is YES answer another question Is the member within 25 feet 7 6 meters of the seawater Based on the above responses and the following table the surface chloride le
229. ty file The commands contained in SETUP PRN are sent to the printer by CORRODE prior to printing any reports When you quit the system CORRODE sends the commands stored in file RESET PRN to the printer to restore its settings to those that existed prior to the run 1 4 System Requirements You will need a personal computer operating under DOS A 286 version system will suffice although 386 or 486 class systems with math coprocessors will improve performance A minimum of 2 megabytes should be available on the hard disk on which you will install CORRODE The data that you define for each bridge treatment analysis and report will require additional disk space You should be able to develop a set of several examples without any concern about disk space However before you input data for many bridges or build an extensive library of treatments that you will be applying in the future you may want to consider the implications of these for disk storage requirements and plan your system installation accordingly 1 5 Useful Keystrokes and Other Conventions Standard keystrokes help you move about the CORRODE program select options and enter data The list below describes standard keystrokes and typical situations in which you would employ them e Navigating through menus and forms Use the up down and left right arrow keys in the normal way to move through a menu list or option list or across the main menu bar at the top of the screen In a
230. ty of the concrete per a suggested test method in Appendix E Distress Rate Resistivity Years to Condition ohm cm Index of 45 High lt 7 500 t 10 Medium 7 500 to 30 000 t 20 Low gt 30 000 t 435 From the appropriate curve the time t to reach S745 can be defined and output to the cost analysis in lieu of S and t Actual adjustments to the deterioration curve will need to be defined 69 70 Flowchart 10 Repair Information Module Year in which previous repair was performed Years to previous repair year in which previous repair was done year in which member was constructed Input area of spall left after repair in square feet typically zero Input area of delamination left after repair in square feet typically zero Calculate percentage of delamination just after repair area of delam area of the member Calculate percentage of spall just after repair area of spall area of member Enter approximate percentage of member left contaminated with chloride after repair If exact percentage is not known choose one of the ranges to the best of your knowledge a 0 15 b 15 30 c 30 50 d 50 75 e 75 100 if a range was chosen then the maximum of that range will be used for approximate calculations Calculate the condition index just after previous repair CL 2 5 DELAM 7 5 SPALL 8 5 This index is taken as equivalent to the index at time to deterioration Was any
231. u either check the corrosion input data or specify a corrective rather than a preventive treatment e CL DL and SP following treatment three separate inputs describing respectively the percent of deck area that following repair is chloride contaminated delaminated and spalled These inputs collectively represent your best judgment of how the repair affects the condition and future performance of the deck For example if patching will repair spalls but will not remove the existing chloride contamination or address delaminated areas you would input zero for SP following treatment indicating that the treatment corrects the current spalling You would then input a nonzero value for chloride and delamination following repair reflecting the likely amounts of these distresses at the time of repair For purposes of this analysis the percent area of chloride contamination is that portion of the deck in which the rebar level chloride exceeds 0 035 percent by weight of concrete This feature may also be used to reflect the quality of work or the reliability of the treatment For example if delaminated areas are to be patched but experience indicates that only 90 percent of the delaminated areas are reliably detected at the time of repair then DL following treatment would be input as 10 percent rather than zero e Nominal life the estimated life of the treatment in years based on your experience and judgment This nominal life establishes
232. u may view the data input forms for each of the sets of technical and cost data by moving the cursor to the respective line on the TREATMENT input submenu and pressing any key when the cursor is on the respective button for that form The button is displayed as a field with a Y in it When you complete data input press F10 to close a data input form save any changes you have made and move to the next button on the submenu Pressing Escape instead will also close the data input form but will not save your changes CORRODE will return you to the same button on the TREATMENT submenu When you press any key thereafter the same data input form will again be displayed e Navigating the data input forms you may move through the fields of the data input forms by using the up down cursor keys or the tab and shift tab keys The following sections describe the information contained in each of the TREATMENT data input forms Cost and Productivity Data You will use the first TREATMENT data input form to describe the cost and time or productivity to perform the treatment Cost and productivity data are organized in parallel lists of cost components and time or productivity components CORRODE will compute the total cost and total time required for a treatment as the sum of the contributions from each of these components Costs will be tallied as part of the agency costs to be accounted for in the life cycle cost analysis The time required for
233. ucture to locate defects Delamination Survey Use 5 foot grid on deck 2 5 foot grid on sub and superstructure to locate all areas of delamination Distinguish between delaminations and spalls Cover Depth The greater of 1 40 locations per member or 2 N 40 A 5000 locations per member where A area in square feet of member Chloride Profiles The greater of 1 10 locations per member or 2 N 10 A 5000 locations per member where A area in square feet of member Corrosion Potential Use 5 foot grid on deck 2 5 foot grid on sub and superstructure Additional measurements required to locate sites of anodic highest potential Corrosion Rate Measurements at sites of anodic corrosion potentials limited to the greater of 1 10 locations per member or 2 N 10 A 5000 locations per member where area in square feet of member Concrete Permeability Resistivity The greater of 1 2 locations per member or 2 N 2 A 5000 locations per member where A area in square feet of member e One foot is 0 305 meter e One square foot is 0 093 square meter 252 Previous Repair When this input form is displayed enter the following data e Year of repair the calendar year in which the previous repair was performed Spalled delaminated chloride areas remaining three separate inputs identifying the estimated areas of spalling delamination and chloride contaminated areas respectively that are estimated to
234. unt factor and fill out the boxes of Column 10 with the products Step 8 Total Present Worth All Strategies Add up all the costs in Column 10 to find the total present worth of each strategy Step 9 Salvage Value Find discounted salvage value of the last treatment and fill out the corresponding box in the bottom of Figure 13 1 Equation 13 3 Strategy Treat at t SLVG COST RS ESL DF SLVG 77 000 40 000 28 20 28 0 474 SLVG 15 845 206 Strategy Treat at t SLVG 241 500 160 000 10 1 10 0 474 SLVG 171 059 Strategy Treat between t and t SLVG 241 500 160 000 14 1 14 0 474 SLVG 176 716 Step 10 Life Cycle Cost Subtract the discounted salvage value Step 9 from the total present worth Step 8 to find the life cycle cost for each strategy Fill out the Life Cycle Cost box in the bottom of Figure 13 1 Strategy Treat at t Life Cycle Cost 136 074 15 845 120 229 Strategy Treat at t Life Cycle Cost 526 961 171 066 355 895 Strategy Treat between t and t Life Cycle Cost 399 431 176 716 222 715 Step 11 Life Cycle Cost Comparison If the deck is treated at the present year 1992 the life cycle cost will be 54 percent of the life cycle cost if it were treated in 1997 and it will be 34 percent of the life cycle cost if it were treated in 2001 Treatment Time Life Cost dollars 1992 120 229 1997 222 715 2001
235. ure when Z is measured years 127 Step 12 Determine the set of data corresponding to the condition index equal to 45 as shown below t age of the concrete at condition index of 45 years determined from Table 6 1 based on the average wet resistivity of the concrete surrounding the reinforcing steel S condition index of 45 Step 13 Use Equations 6 6 and 6 7 or Figures 6 3 and 6 4 to find parameters B and A respectively see Step 6 6 3 Case 3 Concrete not Repaired Rehabilitated and or Protected Previously and with a Special Protection Built at the Time of Initial Construction This category applies to all concretes which were not repaired rehabilitated and or protected against corrosion induced deterioration during their service period and were built with a special corrosion protection system at the time of their initial construction Follow all the steps described in Case 2 Concrete without a Special Protection to find the performance equation However t time to first sign of deterioration should be modified where Equation 6 2 or Figure 6 1 is used based on the type of protective system The following sections present the types of protective systems and procedures to modify t for those systems Concrete Overlays e Conventional Concrete e Low Slump Dense Concrete e Silica Fume Concrete e Latex Modified Concrete 128 Determine a weighted average water cement ratio as shown below based on the
236. urred Based on your response CORRODE will prompt you for information in certain other fields on the form but suppress the others e If so in what year if your response above was yes Y enter the year in which this distress was first noticed This year will define the estimated time to deterioration ta of the bridge deck e Year of surface chloride survey if your response above was no N data on the surface chloride level are required to estimate the time to deterioration of this deck Enter the year this survey was made e Number of surface chloride values enter the number of surface chloride values obtained in the survey At least eight surface chloride levels 0 25 to 0 75 inch depth should be determined per deck or per 5 000 square feet whichever results in the larger number These samples should not be taken in patched areas After you enter this number CORRODE displays an input sheet in which you enter each surface chloride value as a percent CORRODE will use this information to compute the mean and standard deviation of the surface chloride distribution and the estimated thickness at the 90 percent confidence limit When you have finished entering the surface chloride data press F10 Corrosion Analysis Results When all corrosion data have been entered CORRODE will perform the corrosion analysis automatically Note If you think all corrosion data have been entered but the analysis has not started try pressing F10 Eit
237. ve for U Strategy Treat at t Year in Plan Horizon U 1 7 44 4 7 lt 1 000 2 5 8 lt 1 000 3 6 9 lt 1 000 4 7 9 lt 1 000 5 9 0 lt 1 000 6 10 1 lt 1 000 7 11 2 lt 1 000 8 12 3 lt 1 000 9 13 3 lt 1 000 10 14 4 lt 1 000 11 15 5 1 052 12 16 6 1 385 13 17 7 1 790 14 18 7 2 230 15 19 8 2 803 16 20 9 3 480 17 22 0 4 273 18 23 1 5 194 19 24 1 6 153 20 25 2 7 356 203 Fill out the boxes of Column 7 with the user costs Strategy Treat at t Year in Plan Horizon NO 00 10 UA RU tO S 7 1 8 6 10 4 12 6 15 0 17 9 21 2 24 9 29 0 33 5 11 8 14 1 16 4 18 7 21 0 23 3 25 6 27 9 30 2 32 5 35 0 11 8 Fill out the boxes of Column 7 with the user costs Strategy Treat between t and t 204 Year in Plan Horizon l NO Oo ON tA PW VY 7 1 10 4 12 6 15 0 17 9 10 3 12 1 13 9 15 7 U lt 1 000 lt 1 000 lt 1 000 lt 1 000 lt 1 000 1 872 3 684 7 012 12 902 lt 1 000 lt 1 000 1 319 2 230 3 547 5 376 7 835 11 053 15 174 20 352 lt 1 000 U lt 1 000 lt 1 000 lt 1 000 lt 1 000 lt 1 000 1 000 1 000 1 000 1 108 Year in Plan Horizon U 10 17 5 1 710 11 19 3 2 531 12 21 1 3 615 13 22 9 5 016 14 24 7 6 789 15 26 5 8 996 16 28 3 11 701 17 30 1 14 974 18 31 9 18 890 19 33 7 23 528 20 35 0 11 8 1 000 Fill out the boxes of Column 7 with the
238. vel 10 years into the future is estimated Known data include the question answers the present surface chloride Z and the exposure age to date t Snow Range Seawater Surface Clorides inches Exposure in 10 years Greater of 0 to 3 No Z t 10 t or 0 04 3 to 12 No Z t 10 t or 0 10 0 to 12 Yes gt 25 ft Z t 10 t or 0 10 0 to 12 Yes 25 ft Z t 10 t or 0 25 12 No Z t 10 t or 0 25 12 Yes 25 ft Z t 10 t or 0 35 gt 12 Yes lt 25 ft Z t 10 t or 0 45 One inch is 2 54 centimeters one foot is 0 305 meters Then t is calculated based on the appropriate Z from the table above while t in the equation for Z is equal to present t concrete age at the time of measuring surface chlorides plus 10 years Calculation Two Submodule Flowchart 9 The user then must continue the Pre Deterioration Submodule to estimate the concrete condition at some time in the future after ta This is done using the Calculation Two Submodule This estimate is required to determine the slope of the deterioration versus time curve after corrosion is active By this time chloride is present at the reinforcing steel level in excess and the corrosion and deterioration rates will be dictated by many factors including the steel concentration oxygen availability and the resistivity of the concrete in the field All these factors are not known However an estimate of whether the deterior
239. y be taken The first 1s to appropriately increase the area under the corrosion rate line after the treatment The other is to decrease the slope of the after treatment condition index versus time curve such that additional time is realized until S is reached S4 Spo 0 44 SPALL Effective Service Life of Previously Treated Concrete The same total corrosion since initiation philosophy is not literally applicable is the case of previously treated members A special procedure for these concretes is described below The present corrosion rate C can be measured and it is known But the corrosion rate at the past treatment C is not known and neither is t or t for which we have assumed corrosion rates in other analyses Therefore C needs to be estimated To do so we must rely on trends for the type of treatment done We know that 1 ifa sealer membrane or overlay was installed the corrosion rate has remained relatively constant 2 if none of the above items were used the corrosion rate has increased since treatment and 3 since a treatment was previously performed the corrosion rate at that time had to be greater than 1 milli ampere per square foot 10 8 milli amperes per square meter 43 Thus the corrosion rate at treatment needs to be defined as follows e Ifltem 1 above applies the corrosion rate at treatment C is equal to the corrosion rate at present C e IfItem 1 above does not apply the co
240. y be the one that has the best cost results i e its optimal life cycle costs are the lowest among those of all activities considered In some cases however other factors may influence a decision such as the local availability of a repair technology or budget constraints that dictate both the level and the timing of anticipated expenditures Two methods of life cycle cost analysis have been used The first method based on a capitalized cost approach has been devised for the computer program version of the methodology Since this method is not suitable for a handbook solution the second method based on a salvage value approach has been devised for the handbook version of the methodology In both methods life cycle cost is determined in terms of present worth In the computer method an indefinite planning horizon is considered so that the salvage value of the last cycle of treatment will be negligible and therefore need not to be determined However in the handbook method a 20 year planning horizon is considered and a method to obtain the salvage value of the last cycle of treatment is provided Obviously because of the difference in the duration of the planning horizon 47 the life cycle cost of a given treatment will not be the same using these two methods However the critica factor in the methodology is the difference in life cycle cost not the actual value of the life cycle cost The two methods give the same relative life cyc
241. years This optimum is based on considering both agency costs and user costs If user costs were not considered in this problem that is if the decision on overlay timing were predicated solely on agency costs the optimal timing would have been determined to be later in Year 27 More important the region of optimal timing is more clearly defined when user costs are considered Considering only agency costs the least cost value occurs in a very flat part of the curve where the costs of deferral may not be significant enough to justify expenditures against competing bridge needs In other words considering agency costs alone does not introduce the full scope of the benefits of bridge treatments or the full scope of penalties if such treatments are deferred or foregone Comparison of Treatments Analyses such as those described above for overlays were performed for all four treatments listed in Table 2 The results are summarized in Figure 11 showing only the total cost curves for each treatment Bear in mind that these results are for the relatively new and therefore only slightly distressed bridge deck that was considered in the example In this light the results are interpreted as follows 54 Discounted Costs Thousands 100 90 80 70 60 50 40 30 20 10 Eme l 3 Patching 5 7 9 Figure 11 Comparison of Treatments Sealer ll 13 15 17 19 2 23 25 27 29 Time at Which Treatment Is Perform
242. zation procedure will provide the following information on each activity considered The recommended timing of the activity based on the minimization of life cycle costs and e The total discounted agency and user costs for that activity if it is performed at the recommended time 48 The optimization procedure is formulated in terms of the following objective function Min J U exp rt dt C S t exp rt U exp rt exp rt 1 d f U m exp rt dt C S 1 exp rl U exp rl Eq 6 1 where J the total discounted life cycle costs to be minimized for a given protective or corrective strategy r discount rate d the present worth factor 1 1 r 1 the life computed for each subsequent deterioration and repair cycle following the initial one Figure 6 m periodic cost of maintaining the repair treatment in this model only cathodic protection Other variables are as defined for Equations 2 1 through 4 3 The total cost J is the sum of the costs in three periods of the analysis The first integral expression which applies from time t 0 to t represents the discounted user costs prior to any treatment Routine maintenance costs for the deck could also be easily included here if desired The expressions for C S t and U represent the agency cost and the incremental user costs respectively during the construction period for the treatment The expression in the braces represents the co

life-cycle cost analysis for protection and rehabilitation

Contents

Download Pdf Manuals

Related Search

Related Contents