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Life-365™ Service Life Prediction Model™

1. casse Ss Xw conc Compute life cycle cost Settings Help for this window Set default values Years to build to max surface concentration 7 About Life 365 Tips Add new Edit set Delete 70 80 90 100 110 120 130 140 150 Year Temperature History Monthly Temperatures Month Temperature F F January February Default Settings and Parameters Online Help Figure 4 2 New Life 365 Exposure Tab To create a new ASTM set press the Add new button in the panel After prompting for a set name a new empty data set will display in an ASTM data panel Figure 4 3 GGT ASTM calculations setRepot Name double click to edit Max Conc Error 1 Depth 1 must be greater than zero ASTM C1556 Set 0 605 wt conc Error 2 Depth 2 must be greater than zero lt mewset gt Xwtcon Error 3 Depth 3 must be greater than zero Error 4 Depth 4 must be greater than zero Error 5 Depth 5 must be greater than zero Error 6 Depth 6 must be greater than zero Error 7 Depth 7 must be greater than zero Error 8 Depth 8 must be greater than zero Error 9 Depth 9 must be greater than zero Error 10 Depth 10 must be greater than zero r Selected Set new set Conc wt conc 0 0
2. nnen x f 10 0 12 5 15 0 17 5 20 0 22 5 Addarow Delete selected row s Depth mm W Observed Predicted Concentration wt conc o o m Figure 4 4 ASTM C1556 Data When done the ASTM C1556 panel should look something like Figure 4 5 57 ASTM C1556 Estimation of Max Surface Concentration Life 365 2 2 FOR CONSORTIUM REVIEW Project Sets E Some Guidance mx ASTM Calculations Set Report Name double click to edit My New Set Selected Set My New Set Max Conc 0 605 Parameters Sample Depth mm 1 000 2 000 3 000 4 000 5 000 6 000 7 000 8 000 9 000 10 000 15 000 20 000 25 000 Conc wt conc 0 368 0 450 0 410 0 326 0 266 0 231 0 175 0 183 0 132 0 124 0 117 0 080 0 078 Add row Delete selected row s Project Sets My New Set eo ob Concentration wt conc 5 e a 7 5 10 0 12 5 15 0 17 5 Depth mm Observed Predicted Showing the Data Selected Set My New Set Units Sl metric Days 365 Conc wt conc Initial Conc 0 085 Use first point Parameters Panel Figure 4 5 ASTM Panel with Data Entered 4 2 3 Viewing the Results Once the data has been entered the data can be viewed in a number of ways 1 The Sets panel now lists the
3. 293K 20 C The temperature T of the concrete varies with time according to the geographic location selected by the user If the required location cannot be found in model database the user can input temperature data available for the location The chloride exposure conditions e g rate of chloride build up at the surface and maximum chloride content are set by the model based on one of three alternate approaches 1 Life 365 provides a database of values based on the type of structure e g bridge deck parking structure the type of exposure e g to marine or deicing salts and the geographic location e g New York NY 2 The user can input their own data for these parameters The user can calculate a maximum surface concentration based on measured chloride levels using ASTM C1556 and input their own data on time to buildup The solution for time to initiation of corrosion is carried out using a finite difference implementation of Eq 1 where the value of D is modified at every time step using Eq 2 and Eq 3 2 1 2 Input Parameters for Predicting the Initiation Period The following inputs are required to predict the initiation period Geographic location Type of structure and nature of exposure Depth of clear concrete cover to the reinforcing steel and 10 Details of each protection strategy scenario such as water cement ratio type and quantity of supplementary cementitious materials and co
4. Project Exposure Concrete Mixtures Individual Costs Ufe Cyde Cost Service Life Report LCC Report Constant Costs Cumulative Present Value Compute service life 9 9 Define project costs 5 12 5 5 5 Compute life cycle cost a a 4 4 10 0 a Settings 75 Help for this window Set default values 8 5 0 8 20 About Life 365 4 25 ll 10 i LIEU MEHR w 5 5 U MMMM O M W a M ________ 2025 2050 2075 2100 2125 2150 2025 2050 2075 2100 2125 2150 Year v Year Ill Base case Alternative 1 Base case Alternative 1 Current Costs Cumulative Current Costs g g 250 x amp 30 5 200 150 2 201 p 100 amp 10 8 ME i B o lur 8 2025 2050 2075 2100 2125 2150 2025 2050 2075 2100 2125 2150 Year Year Ill Base case Alternative 1 Base case Alternative 1 Default Settings and Parameters Online Help J Figure 3 14 Life Cycle Cost Timelines Tab The lower two panels show the individual year and cumulative current dollar costs which are the costs adjusted for inflation only This current dollar measure is not a measure of life cycle cost but is a useful estimate of the actual dollars that are estimated to be spent over the study period For these particular alternatives
5. Base case E com Modify Initiation Period Uncertainty Probabilities Probability 50 0 25 50 75 100 Show as CDF Reset Year Current Analysis Default Settings and Parameters Online Help Figure 3 27 Life Cycle Costs Tab with Modify Uncertainty Panel When first created this panel sets the Probability slider to 50 which means that there is a 50 percent probability that each concrete mixture s initiation period will be less than the indicated value and a 50 percent probability that it will be more than the indicated value In Figure 3 27 the initiation periods are displayed as 4 and 16 years Modify Initiation Period Uncertainty Probabilities Probability 50 0 25 50 75 100 Show as CDF Reset Figure 3 28 Modify Uncertainty Panel At the 50 percent values all of the life cycle cost graphs should display results identical to or due to rounding errors very similar to the best guess based values computed when uncertainty is not activated 50 The purpose of the slider panel in Figure 3 28 is to allow the user to modify the uncertainty values for each alternative and see what effect the new values have on life cycle cost Since the 50 percent values represent the best guess of each mixture s alternative based on laboratory experiments most other values would be subjective judgments As a minimal constraining factor Life 365 req
6. Chloride at above times wetting and drying profile Initial data needed to required to calculate chloride profiles Mixture establish variability Absorption causes build proportions subsequent tests for up D changes over time Chloride Modified ASTM G 109 Minimum of 6 Replicate test Too late if staining Threshold Visual evidence amp specimens per test program to confirm cracking and delamination Ct chloride profiles see see text values desirable are visible text Corrosion Linear polarization and Research needed Research needed Research needed rate Continuation of ASTM G propagation 109 until cracking time tp 87
7. and t the time step in the initiation to corrosion period Rearranging terms and putting them in matrix form the chloride levels at each time period 1 are solved from the equation AU BU where 17 N 5 zw o ae us umo wee ean O N e N Ej N The individual are then be solved by rearranging terms p A BU The number r is required to be small for numerical accuracy Two Dimension Calculations Square and Round Columns For two dimensional columns the time to initiation ideally can be estimated using a two dimensional Crank Nicolson equation 1 1 r 1 1 1 1 1 1 1 1 t 1 2r u AUT tU tU 1 2r u Eq 9 r t t t 2 tU tU where each term is defined as in one dimensional case above but where each i j term is a square from the ith row and jth column of a square matrix of terms Since the chloride surface concentrations and interior steel locations are symmetric to the vertical and horizontal centerlines of the column cross section we can solve using just one 18 uadrant of the cross section As shown in Figure 2 7 we use the upper left quadrant q pp q where the surface cells are the external levels of chloride and therefore exogenous parameters in the calculations and the interior cells are those to be calculated surface surface surface surface surface interior a interior a int
8. install it To install Java search for Java Runtime Environment JRE on the Internet e g via Google and go to the Oracle website that offers the download of this JRE for your operating system Then download and follow its installation instructions Once completed return to the Applications gt Utilities gt Terminal program and at the command prompt type java version again Your computer should now display the version of Java installed make sure this version is 1 6 or higher If you still have problems installing Life 365 please contact the Life 365 Consortium III at http life 365 org contact html 3 2 Starting Life 365 Installing Life 365 puts a start menu item labeled Life 365 in your Windows Programs folder accessible from the Start button in the lower left hand corner of your screen and an icon on your desktop on Apple computers there should be a Life 365 icon in your Applications folder Other UNIX platforms may not depending on your Java settings To start Life 365 simply select this menu item or the desktop icon When Life 365 starts for the first time it will ask you to select the base units of measure for your projects either in SI metric US units or Centimeter metric This selection will determine whether all of your inputs need to be expressed in for example meters or yards If you decide later to change these base units go to the Default Settings and Parameters tab at the bottom of the scree
9. temperature coordinates may be input by the user by un checking the Use defaults box in the Exposure tab 5 2 1 Surface Concentration The surface chloride concentration is the main driving force for chloride penetration in Life 365 The model selects the rate of chloride buildup and the maximum surface concentration based on the type of exposure and structure and the geographic location Life 365 includes the following exposure conditions Marine splash zone defined as being in the tidal range or within 1 m of the high tide level Marine spray zone defined as being more than 1 m above the high tide level but occasionally exposed to salt water spray Within 800 m of the ocean Within 1 5 km of the ocean Parking garages Rural highway bridges e Urban highway bridges The first four categories are only available for coastal regions For example if the user chooses Tampa Florida as a location all seven of the above options are offered However if Wichita Kansas 1s selected only the last three exposure conditions are offered For structures in a marine environment the model assumes the values in Table 4 Table 4 Build up Rates and Maximum Surface Concentration Various Zones Build up Rate Maximum 95 Marine splash zone instantaneous 0 8 Marine spray zone 0 10 1 0 Within 800 m of the ocean 0 04 0 6 Within 1 5 km of the ocean 0 02 0 6 The values for airborne deposition of chloride vary wid
10. which offers detailed explanations of the key windows and features in the Life 365 Computer Program To start a new project select Open new project from the left hand side navigation menu a complete project will be created for you with two alternatives each of which has a baseline concrete mixture To open a previously created and saved project select Open existing project When a new or existing project is opened the main panel will show seven tabs at the top To conduct an analysis each tab can and should be accessed from left most tab Project to right most tab LCC Report Additionally the left hand Navigator pane has a list of chronological Steps that divides your Life 365 analysis into logical analytical components 1 Define project e g input the title description structure type units of measure and economic values 2 Define alternatives e g input the titles and descriptions of the alternatives that meet the project requirements 29 3 Define exposure input the location and type of structure so as to set the chloride and temperature exposure conditions 4 Define mix designs input the concrete mixture and corrosion protection strategy for each alternative Compute service life calculate the service life of each alternative 6 Define project costs input the initial construction barrier and repair costs and repair schedule 7 Compute life cycle cost calculate and sum the present value of all costs
11. 0 27 Ui j Mia tM the nine equations are then 1 2 gt upi EIN 1 2 U 5 in f 1e27 u3 eu eu Is 2 ups ugs i 0 i t Eq 13 1 1 1 1 1 2755 05 eis 1 2r u ipe 1 1 1 1 141 1 1 Uy tW F Uzo 15 1 2r u i 1 1 1 1 1 1 1 U U U ws u t S A arji cn uy tus x t A 1 27 v 1 1 tuy tus i a 1 1 To be able to solve for each through matrix mathematics the square matrices of and terms are converted to i x 1 matrices e g 20 1 1 1 1 1 1 1 1 Uo o Ho Ud Ho 1 1 1 1 1 Mii Ut 22 7 No ut fu z LJ 1 1 1 1 1 1 Ur Up 7 4 1 1 1 1 1 1 For the 9x9 example then the 0 vector is pu uj and the equations in Eq 13 can be represented by AU The chloride levels at each time period 1 are solved from the equation AU BU 21 or A BU Eq 14 Inverting matrix A however is computationally expensive computing initiation periods could take from 1 to 15 minutes or longer per alternative To overcome this time expense Life 365 uses a successive relaxation technique SOC Validation of Initiation Period Estimates Significant work has been conducted to compare the estimates of initiation period calculated
12. 15 years with associated service life of 16 and 21 years respectively 47 Initiation Period Probability by Year Probability Base case Alternative 1 Figure 3 24 Initiation Period Probability by Year Several important points can be made with this graph first it is hard if not impossible to interpret anything about the probabilistic service lives of each alternative 16 and 21 years respectively from this graph the highest point on each line is the most probable initiation period or most likely to occur but typically not also the average initiation period the expected value of service life Note that this average value is equal to the deterministic value of initiation period calculated when uncertainty analysis is turned off Second peak of the Base case red line is higher than the peak of the Alternative 1 blue line and peaks earlier in years Neither of these however tell us anything about how these uncertainties determine if one of the concrete mixtures has the longest service life in a probabilistic sense that is across the range of initiation periods each mixture can experience To do this we need the cumulative probability density functions shown in Figure 3 25 which simply add each year s individual probability to create cumulative probabilities Cumulative Initiation Per Prob by Year 1 00 Base case Alternative 1 Figure 3 25 Cumulative Initiation Per
13. Base case uncertainty in concrete mix Cost name Start year End year Interval Amount units sq ft Total design initiation times as Base case computed by the methodology used in Item Qtty Amt 5 Construction cost 0 0 0 10 000 sq ft 13 63 136 280 Repair cost 12 150 10 1 000 sq ft 537 16 37 160 Life 3657 see the Users Concrete Cost 926 cub yd 70 796 Manual for details When Rebar Cost 145 520 Ib 65 484 comparing mixes in the left Inhibitor Cost 0 gal 0 panel mix that has a Construction 115 136 280 Cost Timeline for Alternative Base case taller skinnier curve has Barrier cost 0sq ft 50 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 less uncertaintyabout the Repair cost 1 000 sq ft 37 160 service life while a mix with a shorter wider curve has more uncertainty about Construction cost service life This tab is only enabled Repair cost when the above Compute Uncertainty box is checked Default Settings and Parameters Online Help Figure 3 11 Individual Costs Tab Set Concrete Costs In the upper left corner of the screen the Set Concrete Costs tab allows the user to set specific values for the concrete mixture costs Initially this table displays the default concrete cost that is listed in Concrete amp Steel section of the Default Settings and Parameters tab located at the bottom of the Life 365 screen this default cost should represent
14. Cost Service Life Report LCC Report LLLA ELA CIMA Sepa GS Type slabs and walls 1 D Calculate service life V Compute uncertainty Settings Help Figure 3 21 Concrete Mixtures Tab Initiation Time Uncertainty Tab When selected Life 365 will display a small window Figure 3 22 describing this process and then asking for verification that the user wants to conduct this analysis Selecting Yes in this window and then pressing the Recalculate service lives button will invoke the uncertainty calculations thereby adding some new panels to the Concrete Mixtures and Life Cycle Cost tabs If you do select Yes you can later turn the uncertainty calculations off by un checking the same Compute uncertainty checkbox 46 8 0 0 Service Life Uncertainty In addition to computing the best estimate service life of concrete mixes Life365 can also compute the uncertainty in the service lives of mixes Computing this uncertainty in service life is not required for estimating the life cycle cost of alternative concrete mix designs but rather gives additional insight for practitioners that analyze the risks associated with new technology building materials and technologies As such this uncertainty analysis should be considered only useful to the advanced user of Life 365 See the users manual for more details Computing the uncertainty in service life may noticeably slow the performance of Life 365 To turn off u
15. Journal Vol 91 5 pp 447 452 Glass G K and Buenfeld N R 1995 Chloride threshold levels for corrosion induced deterioration of steel in concrete Chloride Penetration into Concrete Ed L O Nilsson and J Ollivier pp 429 440 Maage M Helland S and Carlsen J E 1995 Practical non steady state chloride transport as a part of a model for predicting the initiation period Chloride Penetration into Concrete Ed L O Nilsson and J Ollivier pp 398 406 MacDonald D Pfeiffer D and Sherman M 1998 Corrosion evaluation of epoxy coated metallic clad and solid metallic reinforcing bars in concrete FHWA RD 98 153 Federal Highways Administration Washington D C Mangat P S and Molloy B T 1994 Prediction of long term chloride concentrations in concrete Materials and Structures Vol 27 1994 pp 338 346 78 Manning D G 1996 Corrosion performance of epoxy coated reinforcing steel North American experience Construction and Building Materials Vol 10 5 pp 349 365 Martin Per z B Pantazopoulou S J and Thomas M D A 1998 Finite element modelling of corrosion in highway structures Second International Conference on Concrete Under Severe Conditions CONSEC 98 Tromso Norway June McGrath P and Hooton R D 1997 Effect of Binder Composition on Chloride Penetration Resistance of Concrete Proceedings of the Fourth International Confere
16. Journal Vol 95 5 pp 546 557 80 Appendix A Test Protocols for Input Parameters Background Life 365 is a concrete service life tool that contains algorithms to determine best guess default values for many input parameters These default values are provided to users simply as a place to start The default value algorithms were developed from experimental data and peer reviewed journal articles However developing default values for all potential products and combinations of materials was not practical Default values were included for protection strategies with sufficient published performance data to model reliably It is envisioned that additional strategies will be included in future versions of the Computer Program The limitations of this default value approach were recognized by the model developers so the Program allows allow users to evaluate alternative strategies by entering their own custom project or product specific data This appendix is intended to guide the individual in selecting these custom values It is recommended to obtain the input parameters for Life 365 through the test protocols outlined herein The input parameters used to calculate the time to initiation of corrosion in Life 365 and their location in the Computer Program are shown in Table A1 1 Table A1 1 User Definable Input Parameters Parameter Where it is Input in the Computer Program Maximum surface chloride content Cmax Exposure
17. Prob by Year Using this graph it can be difficult to determine which if either concrete mixture has the longest service life in a probabilistic sense We will therefore attempt here to give a basic example of how to do this Consider for example the values of the red and blue lines at Year 16 on the horizontal axis Given that the blue line is below the red line at this year the probability graph specifically states The blue line Alternative 1 has a lower probability of being 16 years or less than the red line Base case 48 Said differently Alternative 1 is less likely to have a service life of 16 years or less than the Base case If instead we say the converse of the above italicized statement we get a more understandable statement Alternative 1 has a higher probability than the Base case of having a service life longer than 16 years That is Alternative 1 by being below the Base case has a higher probability of having an initiation period longer than that many years Since it is below the Base case line for all values above 12 years it is a reasonable conclusion that Alternative 1 has a longer service life in a probabilistic sense The usefulness of this dominance can be summarized as follows If one of the cumulative probability lines is below the others for all years in the study period or almost all of the years then the corresponding alternative has the statistically longest initiation period Sou
18. The propagation period 5 is fixed at 6 years In other words the time to repair 5 is simply given by t 6 years The only protection strategy that influences the duration of the propagation period is the use of epoxy coated steel which increases the period to t 20 years The user can change the propagation period to reflect local expertise 23 2 3 Repair Schedule The time to the first repair is predicted by Life 365 from a consideration of the properties of the concrete the corrosion protection strategy and the environmental exposure The user needs to estimate the cost and extent of this first repair 1 the percentage of area to be repaired and the fixed interval over which future repairs are conducted 2 4 Probabilistic Predictions of Initiation Period Life 365 includes probabilistic predictions of the initiation period based on Bentz 2003 These predictions are calculated using the following steps a Estimate time to first corrosion for the best guess or average values of the inputs that is the values input by the user b For each of five specific input variables D Cs m estimate five additional time to first corrosions where each is individually adjusted by 10 percent c Use the results of steps b and step a to estimate the derivative of corrosion initiation time with respect to each of the five variables This determines the sensitivity of initiation period to variations in
19. a concrete sample following ASTM C1556 Note the ASTM C1556 specifically discards the first or top most layer for the chloride concentration measurement e Life 365 uses three units of measure SI mm SI cm and US and for each chloride concentration wt concrete kg m3 or Ib y3 respectively The concrete sample data will need to be converted to one of these three units of measures For example chloride concentration data expressed in parts per million will need to be converted to say wt concrete by dividing the values by 1 000 000 and then multiplying by 100 so that a number such as 10 000 ppm is expressed as 1 The initial chloride concentration of the concrete expressed in the same units as the depth concentration data e The time duration of the concrete exposure to chlorides in days 4 2 2 Inputting the Data To input chloride concentration data into a Life 365 project access the Exposure tab in the project Figure 4 2 select Set values manually and then select ASTM C1556 55 Current Project Save project Save project as Method for Setting External Concentration and Temperature Profile Close cd dis Use defaults Location NewYork Sub location NEW YORK Exposure Parking garages Steps Set values manually below Define project hloride sure user defin Define alternatives Concentration Surface Concentration Manual 0 800 wt conc Define project costs
20. and Environmental Engineering Iowa State University 64 5 Life 365 Background Information Life 365 has been produced as a first step in the development of a more comprehensive model for predicting the life cycle cost associated with reinforced concrete structures exposed to chlorides The processes of chloride transport loss of passivity on embedded steel corrosion of the steel and subsequent damage of the surrounding concrete are highly complex phenomena and not completely researched and understood Consequently it is necessary to simplify the assumptions where insufficient knowledge is available All models do this to a certain extent This does not necessarily invalidate the model but it does place a responsibility on the authors to ensure that users of the model are made aware of important assumptions and limitations The purpose of this section of this document is to provide an explanation of the assumptions used in the development of Life 365 the sources of supporting information and the limitations of the model Suggestions are also made to indicate how improvements might be made in the modeling approach as more data become available Validation of estimates from the model to the service life of actual structures is also an important activity that can further improve the model s output 51 Service Life Estimate The service life is defined as the period between construction and the time to the first repair t The tim
21. and go to the website that offers the download of this JRE Since Life 365 will run on Java 1 7 install the most recent version of Java which at the time of this manual s release is Java 1 7 Then download and follow its installation instructions Once completed return to the Control Panel Java Settings Panel Your computer should now display the version of Java installed make sure this version is 1 7 or higher 3 1 2 If Problems Installing on Apple or Linux Computers 1 To see if Java is installed on your Apple computer start the Applications gt Utilities gt Terminal program and at the command prompt type java version Figure 3 2 If Java is in fact installed your computer will then return which version of Java is installed make sure this version is 1 7 or higher If it is not installed the computer will return command not found or similar If your computer runs a non Apple Unix operating system see that system s users manual for information for determining if and which version of Java is installed 27 eoo A life365 bash 80x24 localhost life365 java version java version 1 7 0 17 Java TM SE Runtime Environment build 1 7 0 17 b02 Java HotSpot TM 64 Bit Server VM build 23 7 b01 mixed mode localhost life365 Figure 3 2 Determining Current Java Version in Mac OS X Terminal Console 2 If Java is not installed or you do not have at least Java 1 7 7 0 you will need to
22. be incorporated in future versions The user is encouraged to examine the influence of m by comparing different values in user defined scenarios 73 8 7 8 12 3 8 MI 3 amp ise 3 8 Qa p E T EL EE i FH o p 5 Tr 8 amp gt 2 2 S a S 5 6 5 O 855 E 25 aM T n 2 2 T T I I D o o o o o o o o o m 5 308 0809 uoisnyip juareddy S W UOISNYIp jueJedi u6121j809 juejeddy ett uatotyeoo uorsnylp juereddy Age years Figure 5 5 Effects of Age on Diffusivity 74 To reflect the completion of hydration it is reasonable to assume that there is some limiting value of diffusion coefficient of the concrete mixture In Life 365 the diffusion coefficient decays with time according to Eq 2 until the concrete reaches the age of 25 years at which point the diffusion coefficient remains constant for the rest of the analysis period 1 D D25 for t 25 years 5 2 4 Chloride Threshold There is a vast quantity of published data related to the chloride threshold in concrete The concept of having a single value belo
23. build up rates and maximum surface concentrations The Life 365 values are easily overridden by un checking the Use defaults box in the Exposure tab 5 2 2 Diffusion Coefficient PC Concrete Life 365 assumes a time dependent diffusion coefficient as defined by Eq 2 through Eq 5 of this document The value of D is dependent on the water cementitious material ratio w cm of the concrete Eq 4 and a relationship between D s and w cm was developed for the model using unpublished data from tests at the University of Toronto and published data from the same type of test Only data from bulk diffusion tests similar to the procedure outlined in the Scandinavian standard test NT Build 443 were used in the analysis Sandberg and Tang 1994 Frederiksen et al 1997 Tang and Sorensen 1998 Stanish 2000 Steen 1995 Sandberg et al 1996 This test involves exposing a fully saturated concrete specimen to a chloride solution in such a way that unidirectional diffusion is the only mechanism of chloride transport After a specified period of immersion samples are ground from the exposed surface in precise depth increments e g 1 mm increments and these samples are analyzed for chloride content The diffusion coefficient is then found by fitting a standard numerical solution often called the error function solution of Fick s second law of Diffusion to the experimental data Figure 5 3 shows the relationship between D2 and w cm for con
24. by Life 365 v2 2 against those of other models With regard to 1 D slab and wall estimates the Life 365 v2 2 estimates have been compared to both Fick s second law Error Function Solutions as well as Life 365 v1 1 estimates With regard to 2 D square and round columns the Life 365 v2 2 estimates have been compared to Life 365 v1 1 estimates For the 1 D case in particular work has been conducted to compare the Life 365 v2 2 estimates and indirectly the Life 365 v1 1 estimates of initiation period to Fick s second law error function solution x c x t c I er Eq 15 V4Dt where c x t is the concentration at depth x and time 7 c is the surface concentration erf is the error function and D is the diffusion coefficient which for particular settings are theoretically equivalent Tests of estimates by the two methods show a good fit of the two concentration values shown in Figure 2 9 Table 3 Life 365 v2 2 and ERF Comparison Slab Rebar Surface Init L365 ERF Avg Depth Depth Conc Conc D28 Init Init Diff mm mm 9owt wt m m s yrs yrs wt 0 200 0 10 0 1 000 0 050 8 870E 12 0 1 0 1 0 02641412 1 200 0 20 0 1 000 0 050 8 870E 12 0 2 0 2 0 00321595 2 200 0 30 0 1 000 0 050 8 870E 12 0 5 0 5 0 00143871 3 200 0 40 0 1 000 0 050 8 870E 12 0 8 0 8 0 00137160 4 200 0 50 0 1 000 0 050 8 870E 12 1 2 1 2 0 00138123 5 200 0 60 0 1 000 0
25. computer likely does not have Java installed or does not have at least Java 1 7 installed 1 To see if Java is installed on your Windows computer access the Control Panel and then double click on the Java icon if you do not have a Java icon in the Control Panel then you very likely do not have Java installed In the panel that opens select the Java tab and then the Runtime settings or similar tab On this panel there should be a list of Java versions installed check to see that Java 1 7 or higher is installed and enabled Depending on the version of Windows the 26 panel will look something like Figure 3 1 in this particular figure there is only version 1 7 installed make sure other versions are not checked Life 365 will ask this particular computer s Windows for a sufficient version and will get the version it needs 1 7 f 1 5 Java Runtime Environment Settings E User System Platform Product Location Path Runtime Parameters Enabled 1 7 1 7 0 45 ttp fiava s KE ProgramFllesUava _____ Figure 31 Windows Java Settings Panel You can also optionally verify that Java is installed by accessing the page http www java com en download installed jsp If you do not have Java installed or your installed version is less than Java 1 7 6 0 you will need to install it To install Java search for Java Runtime Environment JRE on the Internet e g via Google
26. each of the input variables d Use the results from step c to estimate a single parameter of variability similar to a standard deviation for a log normal assumed variation of time to corrosion initiation shown by Bentz to work well where the average value of this distribution is taken from the deterministic analysis in step a and the variability of this assumed distribution is determined from the results of steps b and c 2 5 Estimating Life Cycle Cost To estimate life cycle cost Life 365 follows the guidance and terminology in ASTM E 917 Standard Practice for Estimating the Life Cycle Cost of Building Systems This includes the process of 1 Defining a base year study period rates of inflation and discount project requirements and alternatives that meet project requirements 2 Calculating the present value of future costs 3 Reporting results in present value constant dollar and current dollar terms and 4 Conducting uncertainty and sensitivity analysis User Input Parameters The user is responsible for providing the following cost information needed for the life cycle cost analysis Cost of concrete mixtures including corrosion inhibitors for the various corrosion protection strategies under consideration Cost coverage percent of surface area and timing of repairs Inflation rate i and e Real discount rate r Life 365 provides the following default costs for the included rebars 24 e
27. few of these have been validated or calibrated with field data In view of the complexity of the corrosion process a common approach has been to assign fixed values of time to the propagation period based on empirical observations This approach has been adopted by Life 365 5 2 Input Parameters for Calculating the Service Life Time to First Repair Life 365 requires the following data to calculate the time to first repair t Surface concentration kg m Ib yd This 1s the chloride concentration at the surface of the concrete This can be input as a fixed value or allowed to increase linearly with time up to a maximum value and thereafter remain constant The rate of build up and maximum value can be default values within Life 365 based on the geographic location and nature of the structure or can be input by the user This version of the model includes user input for ASTM C1556 data that can impact this input value Diffusion coefficient m s in s This is a material property that is either default values set by Life 365 on the basis of concrete mixture proportions provided by the user or inputted directly by the user in the Set own concrete properties section of the Concrete Mixtures tab This version of the model includes user input for ASTM C1556 data that can impact this input value Diffusion decay index dimensionless This property describes the time dependent changes in the diffusion coefficien
28. for each alternative and compare Each of the software tabs that execute these steps is discussed in turn 3 3 Project Tab The Project tab allows you to complete Steps 1 and 2 above specifically to name the project and set the type and dimensions of the structure the economic analysis parameters and the number and names of the alternative projects Figure 3 4 Project Settings Life 365 v2 2 lt new project gt July 12 2013 Current Project Project Exposure Concrete Mixtures Individual Costs Life Cycle Cost Service Life Report LCC Report Save project z Save project as Identify Project Export project data Title New Project Analyst Analyst Close project Description Default settings for a new project Date 07 12 2013 Steps Select Structure Type and Dimensions Define project Define alternatives Type of structure slabs and walls 1 0 Depth modeled 10 00 Define exposure 22 00 Define mix designs Thickness in 30 0 7 Compute service life Define project costs Reinf depth in 2 0 30 00 ih Compute life cycle cost Settings Area square ft 10000 Help for this window Volume of concrete 925 9 cub yd Set default values About Life 365 Chloride concentration units wt conc Tips Life 365 will model service life for depths up to 10 0 see Users Manual for discussion Define E
29. in the treated concrete relative to the untreated concrete after 21 days of soaking in 15 percent NaCl solution For example the data from NCHRP 244 Table B 30 indicates the reference concrete gained 0 235 percent and silane treated concrete had gained 0 050 percent The initial efficiency factor e is therefore 0 787 or 79 percent e 0 235 0 050 0 235 0 787 If the efficiency is expected to degrade over time confirmation of the product s effectiveness should be obtained in a similar manner In such cases the sealer efficiency should be tested as a function of time or depth of abrasion The relative chloride build up from a cyclic ponding exposure history is also an appropriate means to verify the efficiency factor Chloride content data obtained from a controlled comparative study such as the ASTM G109 procedure or from side by side field exposure studies is acceptable The relative rate of chloride build up should be calculated from samples representative of the top 10 mm of concrete that have been corrected for the initial chloride content as described above Side by side exposure panels are particularly suitable in situations where environmental conditions may have affects on sealer installation 83 Concrete temperature history The default values used for the concrete temperature history are 30 year normal mean monthly air temperatures for North America The user can change these values in the Exposure tab by un ch
30. increase or decrease the value Life 365 assumes that fly ash and slag do not affect the value of D2 but that they do significantly influence the time dependent nature of the diffusion coefficient see below Other materials such as metakaolin may be expected to have a beneficial effect on either the initial value of the diffusion coefficient or the degree to which the diffusivity reduces with time However there are insufficient data to develop a general relationship within the model and the user is referred to the published literature and encouraged to input these materials as user defined scenarios Due to the limitations of the default diffusion coefficient values for concrete mixtures with supplementary cementitious materials the module that allows the input of data obtained from C1556 measurements can provide a better input to the model 5 2 3 Diffusion Decay Index m A number of studies have shown that the relationship between diffusivity and time is best described by a power law Bamforth 1998 Thomas and Bamforth 1999 Tang and Nilsson 1992 Mangat and Molloy 1994 Maage et al 1995 where the exponent is potentially a function of both the materials e g mixture proportions and the environment e g temperature and humidity The following equation has frequently been suggested in the literature where D t Dref diffusion coefficient at some reference time tef and diffusion coefficient at time f m cons
31. information to the clipboard or to export the raw data from the figure or table 43 Initiation Cross section Properties Copy Save as Print Zoom In Zoom Out Auto Range Display in own window Copy graph to clipboard Figure 3 18 Pop up Menu for Copying a Graph to Clipboard 3 9 Supporting Features In addition to the main project level windows Life 365 includes a window for setting default settings and parameters to be used in all of your analysis and a window offering context sensitive help 3 9 1 Default Settings and Parameters The Default Settings and Parameters tab shown in Figure 3 19 allows the user to edit the parameters that are common across the different analyses such as the units of measure location of project economic conditions and concrete costs Life 365 v2 2 new project July 12 2013 Project Settings Current Project Save project Save project as Export project data Close project Steps Define project Define alternatives Define exposure Define mix designs Compute service life Define project costs Compute life cycle cost Settings Help for this window Set default values About Life 365 Tips Default Units of Measure Base Units US units Concentration Units wt conc Default Region and Exposure Conditions Location New York Sub location NEW YO
32. manufacturers product literature Specific products are referenced for informational purposes only Users are urged to thoroughly read this Manual so as to fully understand the capabilities and limitations of the Life 365 Service Life Prediction Model and the Computer Program 1 Introduction The corrosion of embedded steel reinforcement in concrete due to the penetration of chlorides from deicing salts groundwater or seawater is the most prevalent form of premature concrete deterioration worldwide and costs billions of dollars a year in infrastructure repair and replacement There are currently numerous strategies available for increasing the service life of reinforced structures exposed to chloride salts including the use of e low permeability high performance concrete chemical corrosion inhibitors protective coatings on steel reinforcement e g epoxy coated or galvanized steel corrosion resistant steel e g stainless steel non ferrous reinforcement e g fiber reinforced plastics e waterproofing membranes or sealants applied to the exposed surface of the concrete e cathodic protection applied at the time of construction and combinations of the above Each of these strategies has different technical merits and costs associated with their use Selecting the optimum strategy requires the means to weigh all associated costs against the potential extension to the life of the structure Life cycle cos
33. new data set the maximum surface concentration and their units of measure The maximum surface concentration value listed in the table is the value that can be used in a Life 365 project analysis As shown in Figure 4 6 the ASTM Calculations tab lists all of the calculations used and specified by ASTM C1556 for fitting the concrete data to Fick s second law 58 eoe ASTM C1556 Estimation of Max Surface Concentration Life 365 2 2 BETA FOR CONSORTIUM REVIEW Ea Some Guidance Project Sets Graph 1 Set Report Name double click to edit Max Conc Units Table 1 Results New Set 0 605 wt conc Cs Ci Da t 0 605 4 86E 13 Selected Set My New Set Table 2 Calculations Set Data x Measured Value Predicted Value Meas Pred Error 2 1 000 0 368 0 530 0 00E0 0 00E0 Units 5 Days 365 2 000 0 450 0 458 8 20E 3 6 72E 5 REM 3 000 0 410 0 391 1 94E 2 3 76E 4 0 085 4 000 0 326 0 329 3 31E 3 1 10E 5 5 000 0 266 0 275 9 49E 3 9 01E 5 C Use first point 6 000 0 231 0 230 1 25E 3 1 55E 6 7 000 0 175 0 192 1 71E 2 2 93E 4 8 000 0 183 0 162 2 08E 2 4 34E 4 9 000 0 132 0 139 7 07E 3 5 00E 5 10 000 0 124 0 122 2 16E 3 4 66E 6 15 000 0 117 0 089 2 85 2 8 12 4 20 000 0 080 0 085 25 16E 3 2 66E 5 25 000 0 078 0 085 7 00E 3 4 90E 5 Conc wt conc Initial Conc Figure 4 6 ASTM Panel ASTM Calculations Tab 4 2
34. of Reinforcement Field and Laboratory Studies for Modelling and Service Life Feb 1 2 1995 Tang L and Nilsson L O 1992 Chloride diffusivity in high strength concrete at different ages Nordic Concrete Research pp 162 171 Tang L and Sorensen H E 1998 Evaluation of the Rapid Test Methods for Measuring the Chloride Diffusion Coefficients of Concrete Nordtest Project No 1388 98 SP Report 1998 42 Thomas M D A and Bamforth P B 1999 Modelling chloride diffusion in concrete effect of fly ash and slag Cement and Concrete Research Vol 29 pp 487 495 Titherington M P 1998 The Influence of Steam Curing on the Chloride Resistance of High Performance Concrete M A Sc Thesis University of Toronto Tuutti K 1982 Corrosion of steel in concrete Swedish Cement and Concrete Research Institute Report No 4 82 Weyers R E Fitch M G Larsen E P Al Quadi I L Chamberlin W P and Hoffman P C 1993 Concrete Bridge Protection and Rehabilitation Chemical Physical Techniques Service Life Estimates SHRP S 668 Strategic Highway Research Program National Research Council Washington D C 357 p Weyers R E 1998 Service life model for concrete structures in chloride laden environments ACI Materials Journal Vol 95 4 pp 445 453 Weyers R E Pyc W and Sprinkel M M 1998 Estimating the Service Life of Epoxy Coated Reinforcing Steel ACI Materials
35. requires Java 1 7 or higher also known as Java 7 0 or higher Mac OS X now strongly prefers Java 1 7 which can be installed from the Java website Windows Java 1 6 and higher is produced by Oracle and can be installed by accessing http java sun com and then selecting the appropriate web page for installing the most recent version of the Java Runtime Environment JRE To install Life 365 from either a CD or the Life 365 website http www life 365 org On Windows computers o Uninstall any previous versions of Life 365 v2 0 or higher that are installed on the computer by going to the Windows Control Panel accessing the or Remove Programs application and removing these versions of Life 365 o Once removed access the new version of Life 365 and then double click your mouse on the Windows install file this will run through a quick installation program that among other things puts a program start icon in your Programs folder On Apple OS X computers o Double click your mouse on the Apple install file this will mount a disk drive on your desktop Open the disk drive and drag the Life 365 program into your Applications Folder o Different versions of Life 365 can run simultaneously on Mac OS X although we recommend using only the most recent version 3 1 1 If You Have Problems Installing on Windows Computers If the installation process exits abruptly without apparently installing any files your
36. step and 16 e The diffusion constant is uniform over the depth of the element For concrete slabs one dimension calculations the diffusion process is only active in the top portion of the slab and therefore only modeled in Life 365 in the top 10 inches of a slab that is deeper than that Figure 2 6 Depth modeled 10 00 00 in O Life 365 will model service life for depths up to 10 0 see Users Manual for discussion Figure 2 6 Limited Modeling of Diffusion in Slabs Deeper than 10 Inches One Dimension Calculations Walls and Slabs For the one dimensional slabs and walls the time to initiation is estimated deterministically using a one dimensional Crank Nicolson finite difference approach where the future levels of chlorides in the concrete are a function of current chloride levels Specifically the level of chloride at a given slice of the concrete i and next time period 1 is determined by ru 1 2r u ru rui 1 2r ru ru 1 1 1 1 where dt r m is dimensionless Courant Friedrichs Lewy CFL number d the diffusion coefficient at time t in meters squared per second dt the time step in seconds dx the distance increment total depth divided by number of slices u chloride level Yowt of concrete at time and slice 7 i 1 Iis the particular slice of concrete and i 0 is the top slice that holds the external concentration of chlorides
37. tab Max surface conc Rate of surface chloride build up k Exposure tab Time to build to max yrs Sealer efficiency factor e Concrete Mixtures tab Initial efficiency Concrete temperature monthly history Exposure tab Temperature History Concrete cover Xq Project tab Thickness 1D or Width 2D Apparent chloride diffusion coefficient 028 Concrete Mixtures tab D28 Diffusion decay index m Concrete Mixtures tab m Critical chloride threshold for corrosion initiation C Concrete Mixtures tab Corrosion propagation time tp Concrete Mixtures tab Prop period Recommended Test Protocols Maximum surface chloride concentration Cmax The maximum surface concentration Cmax is a function of the environment and concrete porosity Theoretically Cmax is the amount of chloride at the concrete surface In practice the surface concentration is determined from the chloride content of the outer 5 to 10 mm of concrete The default values used in Life 365 were developed through experience but can be adjusted by entering user values in the Max surface conc field in the Exposure tab of the Computer Program Adjustments to Cmax are justified when concrete is placed in non typical environments such as highly concentrated or dilute brine solutions chloride contaminated soils or when local data indicates that the default values are unreasonable or unjustified 81 Theoretical maximum surface concentrations can be calculated from the solu
38. the upper right Cumulative Present Value gives a good explanation of why Alternative 1 the blue line in the graph has lower life cycle cost while it does have a slightly higher cost at initial construction and identical repair costs it has fewer repairs due to the longer service life specifically its first repair occurs later resulting in a total level in the last year of the study period that is lower than the Base case the red line Sensitivity analysis An important component of life cycle analysis is sensitivity analysis or determining how sensitive your results are to changes in any of the underlying assumptions or inputs for economic concrete constituent material or repair costs After making your first best guess estimates of these parameters in the previous tabs Life 365 gives you at least two ways of conducting sensitivity analysis the first way is to simply change any of the parameters in the previous tabs and see what effects it has on each alternative s life cycle cost For example you can easily change the environmental conditions of the mixtures e g switching location from New York NY to Philadelphia PA or some of the properties of your mixtures A second efficient way to conduct sensitivity analysis on a subset of all parameters is to use the Sensitivity Analysis tab Figure 3 15 In this tab you select one of the predefined parameters listed in the left hand tree Discount rate is selected in the figur
39. units Days the age of the sample when measured and Initial conc the initial chloride concentration of the sample If significantly incorrect any one of these parameters could cause significant deviations in the estimated surface concentration of chlorides used in Life 365 The precision of the ASTM estimate of surface chloride concentration is sensitive to the number of samples While the ASTM C1556 Method does not specify a minimum number of samples of depth and concentration the user should attempt to see how sensitive their estimates are to this number 60 ASTM C1556 Estimation of Max Surface Concentration Life 365 2 2 Sets ASTM Designation C1556 11 Standard Test Method for Determining the Apparent Chloride Diffusion Coefficient of Cementitious Mixtures by Bulk Diffusion Life 365 allows users to input chloride concentration data taken from field samples Life 365 does not require that the data be gathered this way but rather that it simply conforms to the number and depth of samples that can be created using the ASTM process The ASTM Standard Method suggests that data be gathered at the following intervals where thie table expresses values in millimeters mm 1 inch 25 4mm Table of Suggested Measurement Depths by w cm source ASTM Depth 1 Depth 2 Depth 3 Depth 4 Depth 6 Life 365 does follow the ASTM C1556 procedure for estimating the maximum surface chloride concentratio
40. years of exposure Preferably sampling should continue on a regular basis thereafter 8 The best fit slope of the time vs adjusted surface chloride content plot is the build up rate for the structure This base build up rate is entered in the Structure Exposure Conditions dialog box Important considerations Rain or maintenance wash downs will reduce the surface concentration Salt crystallization in cracks will increase the surface concentration e Areas which puddle will have higher surface concentrations The mean build up rate for several structures in a region should be used The build up rate for any particular structure will vary over time It is common for chloride to build up rapidly during the first couple years and then stabilize The sealer efficiency factor e The appropriate test protocols for determining the impact of a surface treatment product on the build up rate should include tests on capillary absorption and the relative chloride build up from a cyclic ponding exposure history Capillary absorption is the primary mechanism by which chloride is drawn into the concrete surface and it is therefore indicative of the relative build up rate Products that impart hydrophobic properties to the concrete surface such as sealers should be tested in accordance with the procedures outlined in NCHRP 244 Series I The initial efficiency factor is calculated as the percent reduction in chloride content
41. 00 0 000 0 000 0 000 0 000 0 000 0 000 0 000 0 000 0 000 3 Q wu o OQ u A Uu N m Delete selected row s Figure 4 3 ASTM New Set Data Entry Panel 56 To enter a C1556 chloride data set select the depth field e g Sample 1 and enter the depth value Do the same for the chloride concentration value and then repeat these two inputs for all of the remaining sample data If you have more than 10 rows of data select the Add a row button at the bottom of the screen to add a row When complete if you have extra empty rows select them and then press the Delete selected row s button on the bottom of the screen to delete them When completed with entering the depth concentration data select the Parameters tab and input the Days and Initial Conc concentration values for your data set ASTM C1556 Estimation of Max Surface Concentration Life 365 2 2 E Some Guidance ASTM Calculations Set Report Name double click to edit Max Conc Units ASTM C1556 Set ASTM C1556 Set 0 605 wt conc o Selected Set ASTM C1556 Set Parameters m a o Sample Depth mm Conc wt conc 1 1 000 0 368 2 2 000 0 450 3 000 0 410 4 000 0 326 5 000 0 266 6 000 0 231 7 000 0 175 8 000 0 183 9 000 0 132 10 10 000 0 124 15 000 0 117 _ O 2
42. 050 8 870E 12 1 8 1 8 0 00139729 6 200 0 70 0 1 000 0 050 8 870E 12 2 3 2 3 0 00140854 7 200 0 80 0 1 000 0 050 8 870E 12 3 1 3 1 0 00148045 8 200 0 90 0 1 000 0 050 8 870E 12 3 8 3 8 0 00146977 9 200 0 100 0 1 000 0 050 8 870E 12 4 8 4 8 0 00150216 10 200 0 110 0 1 000 0 050 8 870E 12 5 8 5 8 0 00152166 11 200 0 120 0 1 000 0 050 8 870E 12 6 8 6 8 0 00154075 12 200 0 130 0 1 000 0 050 8 870E 12 8 0 8 0 0 00161298 The Crank Nicolson finite difference approach used in Life 365 v2 2 1 D slab and wall calculation is an approximation to the Fick s Second Law solution and thus an approximation to the error function direct solution To make the comparison a particular set of Life 365 v2 2 parameters must be held constant including the surface concentration over time the diffusion coefficient over time and the external temperature over time The values shown may not exactly match the current version of Life 365 due to continual refinements being made to the codebase 22 Slab Rebar Surface Init L365 ERF Avg Depth Depth Conc Conc D28 Init Init Diff mm mm wt wt m m s yrs yrs 9owt 13 200 0 140 0 1 000 0 050 8 870E 12 9 3 9 2 0 00198084 14 200 0 150 0 1 000 0 050 8 870E 12 10 8 10 7 0 00325238 15 200 0 160 0 1 000 0 050 8 870E 12 12 7 12 1 0 00693507 16 200 0 170 0 1 000 0 050 8 870E 12 15 5 13 7 0 01761402 17 200 0 180 0 1 000 0 050 8 870E 12 22 2 15 3 0 05659158 18 200 0 190 0 1 000 0 050 8 870
43. 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Year Year Base case Alternative 1 Base case Alternative 1 Figure 3 10 Concrete Characteristics Tab 36 For this particular graph the left panel indicates that both mixtures have the same chloride diffusivity characteristics different mixtures could potentially have very different characteristics and thus lines in this graph the oscillations are caused by the effect of annual temperature variation The right hand graph shows that both mixtures have the same surface concentrations this would not be true if the mixtures had membrane or sealant applications 3 6 Individual Costs Tab The Individual Costs tab Figure 3 11 allows you to edit the different constituent cost and cost parameters and view the effects they have on the constituent costs that make up life cycle cost eoo Life 365 v2 2 new project July 12 2013 Project Settings Current Project Save project Save project as Concrete and Repair Unit Costs Export project data Default Concrete and Repair Costs Close project Project Exposure Concrete Mixtures Individual Costs Life Cycle Cost Service Life Report LCC Report Set Concrete Costs 926 cub yd Required user input Steps Alternative User Define project Base case User To accurately capture the costs of your alternative con
44. 4 Using the Surface Concentration Estimate in the Life 365 Project Once the concrete data has be entered and verified the set can be used in a Life 365 project As shown in Figure 4 7 the new set can be used by first selecting Set values manually then selecting ASTM C1556 and then selecting the new set from the drop down import list 59 Project Exposure Concrete Mixtures individual Costs Life Cycle Cost Service Reports LCC Report Select Method for Setting External Concentration and Temperature Profile Use defaults e Set values manually below Chloride Exposure user defined Max Concentration Surface Concentration Manual ASTM C1556 My New Set Add new Edit set Time to Max wt conc Time to build to max yrs Year Temperature Cycle user defined Temperature History Monthly Temperatures Month Temperature C January February March April May June July August September October November December Figure 4 7 Accessing an ASTM Dataset in a Life 365 Project To edit a set in the ASTM C1556 dropdown list select the set and then press the Edit set button To delete the currently selected set press the Delete button 4 2 5 Guidance Tab The second Some Guidance tab at the top provides information how to correctly use this Life 365 application of ASTM C1556 Important guidance includes e Be sure that a particular data set has the correct setting for Unit base units Conc concentration
45. 5E 6 5 000 0 266 7 000 0 175 0 192 1 71E 2 2 93E 4 6 000 0 231 8 000 0 183 0 162 2 08E 2 4 34E 4 7 7 000 0 175 9 000 0 132 0 139 7 07E 3 5 00E 5 8 8 000 0 183 10 000 0 124 0 122 2 16E 3 4 66E 6 9 000 0 132 15 000 0 117 0 089 2 85E 2 8 12E 4 10 000 0 124 20 000 0 080 0 085 5 16E 3 2 66E 5 15 000 0 117 25 000 0 078 0 085 7 00E 3 4 90E 5 20 000 0 080 25 000 0 078 Adda row Delete selected row s Figure 4 9 Verification of Results for Levenberg Marquardt Algorithm The Levenberg Marquardt algorithm requires initial guesses of c and D In the model the default initial guesses are c 1 0 percent weight concrete and D 1x10 meters squared per second A more detailed grid evaluation of ranges of values for these initial guesses c 0 01 2 0 and D Ix10 1x10 yields the same solution values of c and D Levenberg K A Method for the Solution of Certain Non Linear Problems in Least Squares Quarterly of Applied Mathematics 2 1944 pp 164 168 and Marquardt D An Algorithm for Least Squares Estimation of Nonlinear Parameters SIAM Journal on Applied Mathematics 11 2 1963 pp 431 441 62 4 4 ASTM C1556 References Adams T M Pincheira J A and Huang Y H 2002 Assessment and rehabilitation strategies guidelines to maximize the service life of concrete structures Wisconsin Highway Research Program WHRP 02 003 February American Association of State Highway and Transportation
46. 7 _ Area to repair X Fixed repair interval yrs 10 C ins v Constituent costs This tab shows how each Black steel cost 5 0 45 alternative s life cycle cost are generated over time Hover the mouse over the tabs or graphs of each panel in this tab to see more information about what each graph means Life Cycle Cost per sq ft 125 150 175 2 00 Inflation rate 9 o Variation 100 Base case Alternative 1 Current Analysis Default Settings and Parameters Online Help Figure 3 15 Life Cycle Cost Sensitivity Analysis Tab The graph in Figure 3 15 shows the effects of varying the discount rate between 0 percent and 6 percent as indicated by the graph s horizontal axis The graph shows that Alternative 1 has lower life cycle cost than the Base case regardless of the reasonable real discount rate selected that is the life cycle cost effectiveness of Alternative 1 is insensitive to reasonable changes in the real discount rate Sequentially working through all of the parameters in the tree will allow the user to determine if the results are sensitive to any of these input parameters 41 3 8 Service Life and Life Cycle Cost Reports Tabs Finally Life 365 provides two pre defined reports of your project an SL Report for Service Life Report Figure 3 16 and an LCC Report or Life Cycle Cost Report Figure 3 17 These two reports li
47. 8 No data available Figure 5 2 Chloride Levels by Region of North America The maximum surface concentration for parking structures located in the regions where deicing salt use is the greatest light blue in Figure 5 2 is assumed to reach 1 0 wt of concrete Elsewhere the maximum surface concentration for parking structures is assumed to reach 0 8 percent Life 365 applies the factors listed in Table 5 to the surface concentration and build up rates to account for differences in deicing salt use in heavy traffic areas and the wash off that occurs on bridges exposed to rain 69 Table 5 Build up Rates and Maximum by Structure Type Build up Rate year Maximum Parking Structures See Fig 31 1 0 0 8 Urban Bridges 85 percent of value in Fig 31 0 85 0 68 Rural Bridges 70 percent of value in Fig 31 0 70 0 56 The database used to estimate the chloride build up rate and maximum surface concentration in the model is still under development The database needs to be further refined and calibrated using data from structures in the field The database is included in this version of Life 365 only to provide a first cut approximation for users so users are advised to use chloride data from local sources where available Given the preliminary nature of the surface concentration data users are encouraged to compare the output using the values selected by Life 365 against output generated from user defined chloride
48. Black steel 1 00 kg 0 45 Ib e Epoxy coated rebar 1 33 kg 0 60 1b Stainless steel 6 60 kg 2 99 Ib The user should review and if necessary change the costs of these materials to better reflect actual project costs in his area 2 6 Calculating Life Cycle Cost and Current Costs 2 6 1 Life Cycle Cost Present Worth Calculations Life cycle cost is calculated as the discounted present value of the initial construction costs and the repair costs over the life of the structure Figure 2 10 Life cycle cost 1s expressed in either total dollars or dollars per unit area of the structure e g dollars per square meter Construction cost Repair cost Figure 2 10 Construction and Repair Costs over the Life of the Structure The initial construction costs are calculated as the sum of concrete costs steel or other reinforcement costs and any surface protection membrane or sealer costs The present worth of all costs are specifically calculated as follows First Life 365 costs are inputted in terms of what they cost today specifically what they cost in the first year of the study period To compute a cost s discounted present value then it must first be inflated to the future using an annual rate of inflation These inflated costs are the current costs listed I the Life 365 life cycle cost results Each future inflated cost is then discounted to the present value first year using the nominal discount rate n
49. E 12 500 0 17 1 0 68549250 From left to right the table lists the depth of slab depth of reinforcing constant surface concentration concentration to initiate corrosion the constant diffusion coefficient and then the estimates of initiation period by the two techniques and the average differences in the values in the graphs exemplified by Figure 2 9 This figure specifically plots the 60 Life 365 point estimates of concentration one for each slice in the finite difference mesh against the continuous error function estimates Finally it lists whether the ERF value computed is valid specifically whether the error function computed a zero concentration at the depth of the bottom of the slab If it does not then the error function estimate is not directly comparable to the Life 365 estimate The table illustrates how for many of the comparisons done the Life 365 v2 2 estimates are nearly identical to the error function estimates When the error function is not valid however some of the estimates do not compare well at all This is due to the fact that the error function is not reporting a zero concentration at the bottom of the slab when by assumption and design the Life 365 finite difference approach specifically does wt conc Depth mm Life 365 Estimate ERF Estimate Figure 2 9 Life 365 ERF Comparison Over Depth at Time of Initiation 2 2 Predicting the Propagation Period
50. ERAS 74 List of Tables Table 1 Effects of Slag and Fly Ash on Diffusion 14 Table tects of CNDI on Threshold b it o ru wees 15 Table 3 Life 365 v2 2 and Compa rison cccccssscssccssccesncesesscseccseccesacesnnsceceees 22 Table 4 Build up Rates and Maximum Surface Concentration Various Zones 68 Table 5 Build up Rates and Maximum by Structure 70 Table 6 Values of m Various Concrete Mixtures ccccccccccccecsessessssseseessesssssssesecesens 73 Table 7 Doses and Thresholds Various Inhibitors eee 76 Table 8 Model Inputs and Test Conditions onsite peteret ee on ne Y aeree cont denn 87 Life 365 Disclaimer The Life 365 Manual and accompanying Computer Program are intended for guidance in planning and designing concrete structures exposed to chlorides while in service They are intended for use by individuals who are competent to evaluate the significance and limitations of their content and recommendations and who will accept responsibility for the application of the material it contains The members of the consortium responsible for the development of these materials shall not be liable for any loss or damage arising there from Performance data included in the Manual and Computer Program are derived from publications in the concrete literature and from
51. Life 365 Service Life Prediction Model and Computer Program for Predicting the Service Life and Life Cycle Cost of Reinforced Concrete Exposed to Chlorides Version 2 2 1 January 15 2014 eoo Life 365 v2 2 July 12 2013 Project Settings Navigator Open new project Open existing project Settings Help for this window Set default values About Life 365 TM NRMCA NATIONAL READY MIXED CONCRETE ASSOCIATION e Tips Life 365 Service Life Prediction Model EIGER for reinforced concrete exposed to chlorides EPOXY INTEREST GROUP Version 2 2 EUCLID CHEMICAL c ASSOCIATION Default Settings and Parameters Online Help Produced by the Life 365 Consortium Life 365 v1 0 and v2 2 Credits The Life 365 v1 0 program and manual were written by E C Bentz and M D A Thomas under contract to the Life 365 Consortium I which consisted of W R Grace Construction Products Master Builders and the Silica Fume Association The Life 365 v2 2 program and manual are adaptations of these documents and were written by M A Ehlen under contract to the Life 365 Consortium III which consists of BASF Admixture Systems Cortec Epoxy Interest Group Concrete Reinforcing Steel Institute Euclid Chemical Grace Construction Products National Ready mixed Concrete Association Sika Corporation Silica Fume Association Slag Cement Association Life 365 Service Life Prediction Mo
52. Officials 1994 Standard Method for Sampling and Testing for Chloride Ion in Concrete and Concrete Raw Materials T260 94 Washington D C ASTM International 201 1a ASTM C1556 11 Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials 100 Barr Harbour Drive PO Box C 700 West Conshohocken Pennsylvania 19428 2959 ASTM International 2011b ASTM C670 10 Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials 100 Barr Harbour Drive PO Box C 700 West Conshohocken Pennsylvania 19428 2959 United States 2011 Broomfield J P 2007 Corrosion of steel in concrete understanding investigation and repair Spon Press Huang Y H Adams T M and Pincheira J A 2004 Analysis of Life Cycle Maintenance Strategies for Concrete Bridge Decks J Bridge Eng Journal of Bridge Engineering 9 3 250 258 Krauss P D Lawler J S and Steiner K A 2008 Guidelines for Selection of Bridge Deck Overlays Sealers and Treatments Wiss Janney Elstner Associates Inc Northbrook Illinois November 15 109 pp Lamond J F and J H Pielert 2006 Significance of tests and properties of concrete and concrete making materials Philadelphia PA ASTM Lane D S 2006 Laboratory comparison of several tests for evaluating the transport properties of concrete Virginia Transportation Research Lobo C Lemay L and K O
53. RK Exposure Parking garages Economic Parameters Base year e g 2013 2012 Analysis period yrs 150 Inflation rate 1 60 Discount rate Concrete amp Steel Barriers amp Inhib Repairs Concrete cub yd 76 46 Memb S sq ft 3 07 Repair sq ft 537 16 Black stl 5 50 45 Sealer 5 54 0 50 65 Area to repair 10 00 Epoxy coated stl 5 Ib 0 60 Fixed repair interval yrs 10 Inhibitor gal 5 68 Stainless stl 16 2 99 Color Palette Concrete and Cost Graphs Base case Alternative 1 Alternative 2 Alternative 3 Alternative 4 Alternative 5 Set Changes Save Reset to Life 365 default values lt Back to Analysis Current Analysis Online Help Figure 3 19 Default Settings and Parameters Tab 44 Before conducting even your first analysis it is recommended that you access this tab and set the default settings to reflect your own conditions particularly your concrete steel and repair costs and then press the Save button Your first project then will use your best estimates of these parameters 3 9 2 Online Help The Online Help tab Figure 3 20 lists a series of pages describing the functionality of and tips on using each window 8 0 9 Life 365 v2 2 new project July 12 2013 Project Settings Current Project Save project Save project as Export project data Clos
54. Technology NIST ACI and the American Society for Testing and Materials ASTM A detailed report of the workshop 1s available from NIST Frohnsdorff 1999 At this workshop a decision was made to attempt to develop a standard model under the jurisdiction of the existing ACI Committee 365 Service Life Prediction Such a model would be developed and maintained following the normal ACI protocol and consensus procedure for producing committee documents Another mechanism that results in corrosion of steel is carbonation of the concrete cover and the reduction of pH at the level of the reinforcing steel Corrosion due to carbonation is a relatively low probability and is generally associated with lower quality concrete and reduced cover The Life 365 Service Life Prediction Model does not cover carbonation In order to expedite the process a consortium was established under ACI s SDC to fund the development of an initial life cycle cost model based on the existing service life model developed at the University of Toronto see Boddy et al 1999 The funding members of this consortium known as the Life 365 Consortium were Master Builders Technologies Grace Construction Products and the Silica Fume Association Life 365 Version 1 0 was released in October 2000 and later revised as Version 1 1 in December 2001 to incorporate minor changes The current version has many limitations in that a number of assumptions or simplifications have b
55. aking 25 years where the effects of hydration on concrete diffusivity are modeled by m if under these default settings the modeled concrete s diffusivity continues to decline past 25 years Life 365 holds the concrete s diffusion coefficient constant after 25 years Inputting a custom hydration value here changes the number of years after which hydration 34 stops if you set the Hydration yrs field to 5 then hydration will stop after 5 years and the diffusion coefficient will no longer decline it may however still change monthly due to the monthly changes in temperature Chloride concentration necessary to initiate corrosion Inputting this value overrides the initiation corrosions based on the type of reinforcing steel used black steel 0 05 wt concrete epoxy coated 0 05 and stainless steel 0 5 Propagation period Inputting this value overrides the propagation periods based on the type of reinforcing steel used black 6 years epoxy coated 20 years and stainless steel 6 years Service Life Graphs The Service Life Graphs section contains a set of graphs that display the performance of the concrete by time and by the dimensions of the concrete structure Service Life The Service Life tab Figure 3 7 shows the service life of each alternative concrete mixture alternative in terms of the component initiation period and propagation period Service Life Graphs Cross section Initiation Con
56. ashed line indicating the year of initiation Service Life Graphs Service Life Cross section Ele Conc Characteristics Init Prob Init Variation Conc Versus Depth Conc Versus Time at Depth 2 in a 0 75 g 0 04 wt conc 0 i 2 3 4 7 8 9 10 5 6 Depth in Base case Alternative 1 Base case Alternative 1 Figure 3 9 Concrete Initiation Graphs The right graph shows that the Base case mixture hits initiation in 5 years at a rebar chloride concentration of about 0 05 96 weight of concrete while the Alternative 1 mixture hits initiation in 17 years with a rebar concentration of 0 05 weight of concrete Concrete Characteristics Finally the Conc Characteristics tab Figure 3 10 displays two additional graphs that help interpret the performance of the concrete mixtures The left hand side graph Diffusivity Versus Time shows how the calculated concrete chloride diffusivity changes over the initiation periods by mixture The right hand side graph Surface Concentration Versus Time shows how the concrete surface conditions change over the same period Service Life Graphs Service Life Cross section _ Initiation Init Prob Init Variation Diffusivity Versus Time Surface Concentration Versus Time 1 25 x Il 8 0 75 1 001 g x 0 75 8 0 50 8 0 50 t E 2 0 25 0 25 s 0 00 0 00 0 1 2 3
57. ation techniques that minimize crevice corrosion under end treatments are critical Crevice corrosion at the end treatment can cause premature failures The presence of mill scale on the reinforcing will produce lower chloride threshold values 4 Corrosion is a random phenomenon so multiple specimens are necessary 5 Reinforcing steel composition is variable so tests on different heats of steel will produce different absolute values 6 Corrosion requires the presence of oxygen and moisture Concrete that is dry totally saturated sealed or has low water and oxygen permeability will have a higher chloride threshold 7 The chloride threshold is influenced by the pH of the surrounding concrete When the pH drops below 11 corrosion of steel will initiate without chloride 8 Visual observation of corrosion must accompany any test method to properly interpret half cell potential and macrocell corrosion measurements 9 Admixed chloride interferes with some corrosion inhibition mechanisms Corrosion propagation time t Presently there are only a few published studies documenting the impact of corrosion rate on the time from corrosion initiation to cracking In addition there is no industry accepted test procedure for the measurement of t Until an acceptable industry standard is developed the corrosion propagation time may be measured by subjecting the specimens to continued cyclic ponding according to ASTM G 109 type spe
58. bla 2005 Performance based specifications for concrete Indian Concrete Journal 79 12 13 17 McDonald J E and W E McDonald 1991 Evaluation and repair of concrete structures annotated bibliography 1978 1988 Vicksburg Miss Springfield Va U S Army Engineer Waterways Experiment Station Obla K and C Lobo 2005 Laboratory demonstration of advantages of performance specifications Indian Concrete Journal 79 12 22 30 Prowell B D Weyers R E and LL Al Qadi 1993 Concrete bridge protection and rehabilitation chemical and physical techniques field validation Washington D C 63 Strategic Highway Research Program Schlorholtz S and R D Hooton 2008 Deicer scaling resistance of concrete pavements bridge decks and other structures containing slag cement phase I site selection and analysis of field cores Ames Iowa Center for Transportation Research and Education Iowa State University Stanish K D Hooton R D and Thomas M D A 2000 Testing the Chloride Penetration Resistance of Concrete A Literature Review FHWA Contract DTFH61 97 R 00022 University of Toronto Toronto Ontario Canada June 31 pp Trejo D Halmen C and K Reinschmidt 2009 Corrosion performance tests for reinforcing steel in concrete technical report Federal Highway Administration Wipf T J 2004 Effective structural concrete repair Ames Iowa Dept of Civil Construction
59. c Characteristics Init Prob Init Variation Base case Alternative 1 Years W Initiation WB Propagation Figure 3 7 Service Life Tab Cross section The cross section tab Figure 3 8 shows a cross section of the chloride concentration of the concrete mixture at the point of initiation of corrosion The alternative shown is selected from the left hand side Select drop down box Service Life Graphs Service Life Initiation Conc Characteristics Init Prob Init Variation Select Alternative 1 gt Concentration wt conc 0 80 0 67 0 53 0 40 0 27 0 13 0 00 2 00 in Select nearest year 0 to init Year 9 8 MEELETEUEIEE I EU LLLI EA I D Figure 3 8 Cross section Tab 35 The chloride concentration scale on the left hand side indicates the meaning of the colors in the right hand graph The top of the white rebar holes should have a color that reflects the level of chloride concentration at initiation which in this graph is 0 05 wt of concrete Initiation This tab Figure 3 9 shows two graphs the concentration of chlorides at the time of initiation by depth of the structure the left graph Conc Versus Depth and the concentration of chlorides at the rebar depth by point in time up to initiation the right graph Cone Versus Time at Depth The left graph includes a vertical dashed line indicating the depth of reinforcing and the right graph a d
60. cimens until cracking or delamination is detected Continued research on this topic is necessary to advance modeling efforts In the absence of an industry accepted mechanistic model that incorporates the volume of reinforcing the concrete strength the depth of cover and corrosion rate Life 365 has allocated a fixed time period value for corrosion propagation Users opting to modify this value should do so based on experience with similar structures in similar environments 86 Table 8 Model Inputs and Test Conditions Model Input Test Requirement No Tests Frequency Comments Concrete Cover depth survey 1 project Initial Calibrate rebar locator for Cover x Mean and std deviation Data needed to resistivity of concrete establish variability mixture baseline Surface AASHTO T260 Acid 1 500 ft2 or Initial at 2 years Drill amp collect 5 grams of Chloride Soluble 5 minimum per then every 5 years powder from 5 to 10 mm Build up element deep hole with drill Rate k diameter 1 5 max Max Conc aggregate size Cs Sealer NCHRP 244 Series II 1 application area Initial verify reduced absorption efficiency e prior to reapplication Diffusion Bulk Diffusion Da Set of 2 at regular Initial at 1 year then Result depends on the Coefficient interval initially then every 5 years method Develop correlation for 2 cores min per later D changes with age Also need alternate methods sampling minimum of 3 tests Environment effects cyclic
61. conomic Parameters Base year 2012 Analysis period yrs 150 Inflation rate 1 60 Real discount rate 6 2 00 Define Alternatives up to 6 o Add new alt Delete currently selected alt Name double click to edit Description double click to edit Base case A project that uses the normal mix of concrete Alternative 1 A project that uses the a new mix of concrete Default Settings and Parameters Online Help Figure 3 4 Project Tab Identify Project In this section you can set the project Title Description Analyst and Date most of which are used to simply document the project but also are part of the report displayed in and printed from the LCC Report tab Figure 3 17 Select Structure Type and Dimensions In this section you set a number of fundamental parameters about the structure itself Use the Type of structure drop down box to select the structure which also sets the means of chloride ingress e g 1 D one dimensional Use the Thickness for 1 D structures or 30 Width for 2 D structures and Area or Total Length fields to set the total volume of concrete which is used to calculate total concrete installation costs and to set the surface area of the concrete structure which is used to calculate repair costs Use the Reinf depth field to set the distance over which chlorides travel from surface to the steel reinforcement Finally use the Chloride concentration
62. construction barrier and repair costs are provided by the user Life 365 has default values that are supposed to represent typical costs However the user is strongly urged to check all these default values and modify them based on the costs in the local marketplace 54 Summary The solutions provided by Life 365 are only intended as approximations to be used as a guideline in designing a reinforced concrete structure exposed to chlorides The calculated service life and life cycle cost information produced by the model should not be taken as absolute values Many assumptions have been made to simplify the model and make it accessible to engineers who may not have specific expertise in the area of chloride transport and reinforcement corrosion This has resulted in a number of limitations in the model The user is encouraged to run various user defined scenarios in tandem with the Life 365 prediction with minor adjustments to the values e g D s m tp selected by Life 365 This will aid in the development of an understanding of the roles of these parameters and the sensitivity of the solution to their values Finally Life 365 is very much a work in progress It will continue to evolve as further information becomes available 77 References Bamforth P B 1998 Spreadsheet model for reinforcement corrosion in structures exposed to chlorides In Concrete Under Severe Conditions 2 Ed O E Gjerv K Sakai an
63. cost against savings from a reduction in repairs B Construction cost li Repair cost Alternative 1 Online Help Default Settings and Parameters Figure 3 13 Life Cycle Cost Tab Life Cycle Cost This first tab displays the life cycle cost of each alternative in tabular form as a total the colored bars and by component cost the black and gray bars Timelines The Timelines tab Figure 3 14 shows the constituent costs over time This tab will initially show just one of the four timeline figures but can show all four together when the user checks the Show all four time series graphs together box The upper two panels show the individual year and cumulative constant dollar costs that is costs that have been adjusted to account for the effects of increases in the prices of materials and labor the inflation rate and time value of money the real discount rate and that are summed to compute life cycle cost 39 eoo Life 365 v2 2 new project July 12 2013 J Project Settings Current Project Save project eee Save project as Display Life Cycle Cost Export project data Close project Show results as totals unit costs Structure Dimension 10 000 sq ft Steps Life Cycle Cost Timelines Sensitivity Analysis Define project Define alternatives M Show all four timeseries graphs together Define exposure Define mix designs
64. crete at 20 C based on data from this test The data shown represent portland cement concretes without supplementary cementitious materials that were exposed to chlorides at early ages generally 28 days or less and profiled after relatively short periods of immersion generally 28 to 56 days This relationship was developed by Stanish 2000 70 1E 10 C Frederiksen et al 1997 5 A Tang and Sorensen 1998 o 5 1E 11 Stanish 2000 S O Steen 1995 E Sandberg et al 1996 a 1 0612 06 240 wem r 0 719 Sandberg and Tang 1994 1E 12 0 2 0 3 0 4 0 5 0 6 0 7 0 8 wem Figure 5 3 Effects of w cm on Diffusion Coefficient Based on this relationship the predicted early age diffusion coefficient for a portland cement concrete with w cm 0 40 is Dos 7 9 x 10 m s at 20 C This value might seem high compared to diffusion coefficients calculated from chloride concentration profiles for structures in service For instance Weyers 1998 presented D values calculated from chloride profiles for bridges in different states and these values were found to range from 1 0 x 10 m s in northern states to 6 7 10 m s in warmer southern states However these values represent lifetime average diffusion coefficients 1 e the time dependent effects have been averaged out over the period of time from the first salt exposure to the time of sampling and relate to structures exposed to lower average
65. crete mix designs you need to input the actual concrete costs of the Define alternatives Al 1 576 46 mixes in your area There are two types of mixes that need costs 1 the basic mix which has the concrete cost listed in the Define exposure 46 User Default Concrete and Repair Costs tab above and 2 an alternative mix that includes SCMs and inhibitors If you have an Define mix designs alternative mix you need to input the ready mix cost of this concrete in the Set Concrete Costs table to the left Mes By default the Set Concrete Costs table lists the cost of each mix design as the basic mix cost To input the ready mix cost of proj a an alternative mix click on the listed value of that cost in the center column of the table If you need to reset this cost to the Compute life cycle cost basic mix cost uncheck the User box to the right of the cost Settings Note Be sure to review the default values for important constituent costs listed in the Default Concrete and Repair Costs tab Help for this window above Furthermore if any of your concrete mixes include a membrane or sealer and you have inputed your own concrete cost values lt i Calculate costs to the left Life 365 will still add to that concrete cost the cost of the membrane or sealer About Life 365 Tips gt In the Initiation Time Alternatives Uncertainty panel the two graphs show the computed Select Alternative Project Costs for
66. d N Banthia E amp FN Spon London pp 64 75 Bamforth P B 1999 The derivation of input data for modelling chloride ingress from eight year U K coastal exposure trials Magazine of Concrete Research Vol 51 No 2 Berke N S and Rosenberg 1989 Technical Review of Calcium Nitrite Corrosion Inhibitor in Concrete Transportation Research Record 1211 Concrete Bridge Design and Maintenance Steel Corrosion in Concrete Transportation Research Board National Research Council Washington D C Boddy A Bentz E Thomas M D A and Hooton R D 1999 An overview and sensitivity study of a multi mechanistic chloride transport model Cement and Concrete Research Vol 29 pp 827 837 Concrete Reinforcing Steel Institute 1998 Life cycle cost reinforce epoxy coated bar use Concrete Products Penton Media Inc p 82 Frederiksen J M Sorensen H E Andersen A and Klinghoffer O 1997 HETEK The Effect of the w c ration on Chloride Transport into Concrete Immersion Migration and Resistivity Tests Report No 54 Frohnsdorff G 1999 Modeling Service Life and Life Cycle Cost of Steel Reinforced Concrete Report from the NIST ACI ASTM Workshop November 9 10 1998 National Institute of Standards and Technology Report NISTIR 6327 43 p Gjorv O E Tan K and Zhang M H 1994 Diffusivity of Chlorides from Seawater into High Strength Lightweight Concrete ACI Materials
67. d in the Life cycle Cost tab Figure 3 13 38 Life 365 v2 2 new project July 12 2013 Project Settings Current Project Save project Save project as Export project data Close project Steps Project Exposure Concrete Mixtures Individual Costs Life Cycle Cost Service Life Report LCC Report Display Life Cycle Cost Show results as O totals unit costs Structure Dimension 10 000 sq ft Sensitivity Analysis 749 Timelines Construction Cost 13 63 13 63 Define project Define alternatives Define exposure Define mix designs Compute service life Define project costs Compute life cycle cost Table Name Barrier Cost Repair Cost Life Cycle Cost Base case Alternative 1 52 55 52 10 Settings Help for this window Set default values About Life 365 Tips This tab shows the summary total life cycle cost for each of 40 the alternatives and also 5 30 shows the breakdown of these w 20 Graphs Life Cycle Cost by Alternative 50 costs by the major cost components Construction 10 Costs Barrier Costs and Repair Costs Wi Base case 52 55 sq ft Alternative 1 52 1 sq ft Use this tab to determine which alternative is the life cycle cost effective mix design and to understand how each mix alternative Component Costs balances initial construction
68. del and Life 365 are trademarks of the Silica Fume Association These trademarks are used with permission in this manual and in the computer program Table of Contents 1 Introduction 2 Life 365 Service Life Prediction Model 2 1 Predicting the Initiation Period 2 2 Predicting the Propagation Period 2 3 Repair Schedule 2 4 Probabilistic Predictions of Initiation Period 2 5 Estimating Life Cycle Cost 2 6 Calculating Life Cycle Cost 3 Life 365 Computer Program Users Manual 3 1 Installing Life 365 3 2 Starting Life 365 3 3 Project Tab 3 4 Exposure Tab 3 5 Concrete Mixtures Tab 3 6 Individual Costs Tab 3 7 Life Cycle Cost Tab 3 8 Service Life and Life Cycle Cost Reports Tabs 3 9 Supporting Features 3 10 Advanced Analysis Service Life Uncertainty 3 11 Special Applications Epoxy Coated Rebar Top Reinforcing Only 4 Module for Estimating Maximum Surface Concentration 4 1 C1556 Method 4 2 How Life 365 Uses the ASTM C1556 Method 4 3 Software Algorithm 4 4 ASTM C1556 References 5 Life 365 Background Information 51 Service Life Estimate 5 2 Input Parameters for Calculating the Service Life Time to First Repair 5 3 Input Parameters for Calculating Life cycle cost 54 Summary References Appendix A Test Protocols for Input Parameters 23 24 24 24 25 26 26 28 30 31 33 37 38 42 44 45 51 53 53 55 61 63 65 65 67 T7 78 81 List of Figures F
69. e and then select a range of values for this parameter by selecting from 40 the Variations drop down box in the lower left hand portion of the tab where for example a 100 percent variation of an discount rate of 3 percent will create discount rates of between 0 percent and 6 percent Life 365 will then compute the life cycle cost of each alternative across this range of parameters and compare them in the right hand graph The vertical dashed line is positioned at the value of the parameter you selected as your best guess estimate eoo Life 365 v2 2 new project July 12 2013 Project Settings Current Project T E Ee Project Exposure Concrete Mixtures Individual Costs fe Cyde Cost Service Life Report LCC Report Save project Save project as Display Life Cycle Cost Export project data Close project Steps Life Cycle Cost Timelines Sensitivity Analysis Show results as totals unit costs Structure Dimension 10 000 sq ft Define project Sensitivity Analysis Define alternatives Seir Define fex paste Select parameter N Sensitivity to Inflation rate Define mix designs i Compute service life 5 Parameters Define project costs a Compute life cycle cost 7 Discount rate 2 0 Settings Concrete costs Help for this window 5 Repair Cost 37 16 Set default values L Area ti 26 10 0 About Life 365
70. e t may be determined using a quantitative service life model to predict the time to cracking or unacceptable damage for a particular element in a given environment a number of such models exist Many of these models adopt the two stage service life model first proposed by Tuutti 1982 in which the deterioration is split into two distinct phases as shown in Figure 5 1 End of service life Damage O diffusion resistivity CO penetration Time Initiation period f Propagation period f Figure 5 1 Components of Concrete Service Life 65 5 1 1 Initiation Period The initiation period j defines the time it takes for chlorides to penetrate from the external environment through the concrete cover and accumulate at the embedded steel in sufficient quantity to break down the protective passive layer on the steel and thereby initiate an active state of corrosion The length of this period is a function of the concrete quality the depth of cover the exposure conditions including the level of chloride at the surface and the temperature of the environment and the threshold chloride concentration required to initiate corrosion No damage due to chlorides or corrosion is assumed to occur during this period A simple approach to predicting the initiation period is to assume that ionic diffusion is the sole mechanism of chloride transport and to so
71. e project Steps Define project Define alternatives Define exposure Define mix designs Compute service life Define project costs Compute life cycle cost Settings Help for this window Set default values About Life 3657 Tips Online Help Exposure Conditions The Exposure tab allows you to define the environmental conditions to which the concrete structure is exposed These can either be 1 defined using an included database of U S and Canadian locations or 2 inputed directly by the user When your project inputs are completed and you are computing life cycle costs you can conduct sensitivity analysis on the effects of different chloride exposure levels and temperatures by modifying your structure s location and seeing if it changes which alternative is life cycle cost effective Define Location Use defaults Location Sub location Select this option if you want to use the Life 365 database of environmental conditions When checked the fields in the Define Chloride Exposure and Define Temperature Cycle sections will be disabled from user input when unchecked these fields will be available for user inputed values This is either a U S state or territory or a Canadian Province Select the location closest to your project Based on the selection made in the Location box the Sub location box will list either U S cities U S territory cities or Canadian cities Select
72. ears To use this propagation period in the concrete mixtures check the Set own concrete properties box in the Concrete Mixtures tab and enter 15 for the propagation period 52 4 Module for Estimating Maximum Surface Concentration Life 365 v2 2 includes a module that allows users to estimate the maximum surface chloride concentration and for obtaining a more accurate estimate of the apparent diffusion coefficient of concrete mixtures proposed for use on new projects using the measurements of samples from structures or standard specimens exposed to chlorides respectively in accordance with ASTM C1556 This section describes the ASTM test method and how these measurements are used in the Life 365 model 41 ASTM C1556 Method 4 1 1 Definition ASTM C1556 Standard Test Method for Determining the Apparent Chloride Diffusion Coefficient of Cementitious Mixtures by Bulk Diffusion ASTM 2011a aids practitioners by using the chloride content of concrete samples to estimate the apparent chloride diffusion coefficient D and the maximum surface concentration c of the concrete These estimates of diffusion coefficient and surface concentration are based on Fick s second law of diffusion c x t c cpet Eq 1 where x depth from the top surface time since the exposure to the surface chlorides the constant chloride concentration at the surface of the concrete the constant initial chloride concentra
73. ecking the Use defaults box and then entering data in the Temperature History table Concrete cover x The depth of concrete cover varies within a structure This is a user defined input The user should select an appropriate value Users should verify the concrete cover distribution obtained in a structure using appropriate non destructive survey techniques Apparent chloride diffusion coefficient There are numerous test methods being used to determine the chloride diffusion coefficient for concrete but each method produces a slightly different numerical result At the time of Life 365 s first development there was no ASTM C1556 standard so the model developers adopted the Norwegian standard method NT BUILD 443 This laboratory procedure calculates directly from a chloride content profile Both methods should generate similar if not identical estimates of D2s The procedure for obtaining obtain this D s reference value is as follows 1 After 28 days of standard laboratory curing a specimen is surface dried and coated with epoxy paint on all surfaces except the finished surface 2 The specimen is then immersed in a sealed container of chloride solution for 35 days Concrete powder is obtained by dry grinding six 2 mm thick layers from the specimen 4 The total chloride content of the powder samples and initial background chloride content is obtained 5 The initial background chloride content is subtracted
74. een made to deal with some of the more complex phenomena or areas where there is insufficient knowledge to permit a more rigorous analysis Users are encouraged to run their own user defined scenarios in tandem with minor adjustments to the values e g Dos m Cs tp selected by Life 365 This will aid in the development of an understanding of the roles of these parameters and the sensitivity of the solution to the values This manual is divided into five parts 1 Model Description This section provides a detailed explanation of how the Life 365 model estimates the service life time to cracking and first repair and the life cycle cost associated with different corrosion protection strategies The mathematical equations and empirical relationships incorporated in the model are presented in this section 2 Users Manual This section is an operator s manual that gives instructions on how to use Life 365 the input parameters required and the various options available to the user 3 ASTM C1556 Module This section describes how Life 365 provides and uses the ASTM C1556 process of estimating maximum surface chloride concentration based on calculations from field data 4 Background Information This section presents published and other information to support the relationships and assumptions used in the model to calculate service life and life cycle cost A discussion of the limitations of the current model is also presented 5 App
75. ely depending on the environment The default values listed can be considered maximum values Actual values obtained from structures range from 0 004 percent per year to greater than 0 1 percent per year The data indicate the rate of airborne chloride deposition is a function of the frequency of rain and proximity to ocean breezes Very little information is published on this topic so it is advised that users verify the rate of airborne chloride build up and the maximum surface concentration using local data where available 68 The surface concentrations for bridge decks and parking structures exposed to deicing salts are selected from a database developed for Life 365 This database was developed solely as a guide for users and should be verified with local project data The database combines deicing salt application data from surveys performed by the Salt Institute between 1960 and 1984 and data related to chloride build up rates for U S highways from Weyers et al 1993 The database values were also compared against chloride content data collected from miscellaneous parking structures in the United States and chloride data for bridges presented by Babei and Hawkins 1987 The information in the database was used to construct the map in Figure 5 2 which shows how the chloride build up rates vary across North America Ke Build up wt yr lt lt 0 015 0 015 to 0 03 0 03 to 0 06 0 06 to 0 08 gt 0 0
76. endix A Test Protocols for Input Parameters This section provides recommended protocols for determining some of the input parameters used in Life 365 2 Life 365 Service Life Prediction Model Life 365 analyses can be divided into four sequential steps Predicting the time to the onset of corrosion of reinforcing steel commonly called the initiation period ti Predicting the time for corrosion to reach an unacceptable level commonly called the propagation period tp Note that the time to first repair t is the sum of these two periods i e t t tp Determining the repair schedule after first repair and Estimating life cycle cost based on the initial concrete and other protection costs and future repair costs 2 1 Predicting the Initiation Period The initiation period 5 defines the time it takes for sufficient chlorides to penetrate the concrete cover and accumulate in sufficient quantity at the depth of the embedded steel to initiate corrosion of the steel Specifically it represents the time taken for the critical threshold concentration of chlorides C to reach the depth of cover xg Life 365 uses a simplified approach based on Fickian diffusion that requires only simple inputs from the user 211 Predicting Chloride Ingress due to Diffusion The model predicts the initiation period assuming diffusion to be the dominant mechanism Given the assumption that there are no cracks in the concrete Fick s
77. ent time data when plotted as log time vs log D Since the rate of hydration is more rapid at early ages than at later ages it is imperative that calculation of m includes data for concrete at least 5 years old The minimum testing requirement is NT BUILD 443 tests at 28 days 1 year and 5 years age Preferably the concrete should be stored prior to testing in an environment that is similar to that of the intended structure without exposure to chloride Critical chloride threshold for corrosion initiation C The corrosion threshold concentration of chloride is influenced by numerous variables and is therefore not a singular value The C values selected for defaults in Life 365 are conservative estimates and are consistent with the results presented in numerous publications There currently is no standard test procedure to determine the chloride threshold in concrete However reasonable assessment of the chloride threshold values can be obtained from a properly conducted ASTM G 1009 test with the following modifications 1 Cast a minimum of three additional specimens containing reinforcement and three unreinforced specimens for destructive chloride content measurements Pair each unreinforced specimen with a reinforced specimen because corrosion activity will likely initiate at different times in each specimen 2 Monitor the total corrosion current using linear polarization along with the standard macrocell current and half cell po
78. ercent and the long run general inflation was calculated to be 1 8 percent based on the long run nominal discount rate of 3 8 percent and Eq 16 p 25 Private sector projects however can use their own rates of inflation and real discount Define Alternatives Use this section to set the number names and descriptions of alternatives to be analyzed and compared Use the Add a new alt and Delete currently selected alt buttons to create and delete alternatives respectively and double click the mouse on the alternative s Name or Description fields to change them 3 4 Exposure Tab The Exposure tab Figure 3 5 is used to set the exposure of the concrete to external chlorides and to set the monthly temperatures to which the concrete is exposed See Rushing Amy S and Fuller Sieglinde K Energy Price Indices and Discount Factors for Life Cycle Cost Analysis NISTIR 85 3273 18 Gaithersburg MD National Institute of Standards and Technology November 2012 31 eoo Life 365 v2 2 new project July 12 2013 Project Settings Current Project Save project Save project as Export project data Close project Steps Define project Define alternatives Define exposure Project Exposure Concrete Mixtures Individual Costs Select Method for Setting External Concentration and Temperature Profile Use defaults Sub location NEW YORK Life Cycle Cost Service Life Report LCC Repo
79. ercent for buildings exposed to a temperate European climate and 0 2 percent for structures exposed to a more aggressive environment These values refer to total chloride as a percentage of the mass of cementitious materials The range 0 2 to 0 4 percent by mass of cement is equivalent to a range of 0 03 to 0 07 percent by mass of concrete for typical concretes with cement contents in the range 350 to 400 kg m Consequently a value of C 0 05 percent by mass of concrete was adopted for Life 365 Effect of Corrosion Inhibitors As discussed in Section 2 1 2 Life 365 accounts for two corrosion inhibitors at this time these are calcium nitrite and an organic inhibitor Rheocrete 222 also referred to as amines and esters or A amp E in the software These inhibitors are accounted for by allowing the following increase in the chloride threshold level 75 Table 7 Doses and Thresholds Various Inhibitors Dose Threshold C litres m gal cy wt conc Rheocrete 222 5 1 0 12 Calcium Nitrite Inhibitor 10 2 0 15 15 3 0 24 20 4 0 32 25 5 0 37 30 6 0 40 Include a row for concrete without corrosion inhibitors These increased values are based on the results of corrosion studies published in the literature Nmai and McDonald 1999 Berke and Rosenberg 1989 Other inhibitors will be included as published information on their efficiency becomes available The use of an organic inhibitor Rheocrete 2224 a
80. erior b surface interior a interior a interior b surface interior c interior c interior d Figure 2 7 Single Quadrant in 2D Column Also due to symmetry we can represent the interior cells those that need to be calculated by using reflections of certain values specifically particular values in Eq 9 above are represented by their mirror value 1 Interior a points are solved for using Eq 9 above 2 Interior b points are solved for using the following modified version 1 1 1 1 1 1 1 1 t 1 2r u z u y U 1 2r u Eq 10 r 2 3 Interior points solved for using the following modified version 1 1 1 1 1 1 1 1 t 1 2r u z u y HU Ua 1 2r u Eq 11 v Uia Uia j U y LL 4 Interior d points are solved for using the following modified version 1 1 tl 1 1 1 1 t 1 2r u z u nuj Mi M pt Use 1 2r u Eq 12 A atu As an example to solve the interior points at time 1 for 9 interior cells in Figure 2 7 we have 9 equations and 9 unknowns where the variables are declared according to Figure 2 8 19 9 0 0 2 0 3 ho Vp a 3 E Go ar Sa 738 Figure 2 8 Single Quadrant Variables in 2D Column To help simplify the equations given that at time 1 all t values are known the right hand side of each equation can be represented by a function jx H t
81. from the measured total chloride content 6 The chloride diffusion coefficient is back calculated from the adjusted chloride content depth data If the user desires to obtain from other methods correlation between the alternate method and NT BUILD 443 must be established It is important to note that the NT BUILD 443 test method is a laboratory test performed under saturated conditions In this controlled environment chloride diffusion is the primary chloride transport mechanism Concrete structures that are partially saturated may experience chloride ingress from multiple transport mechanisms Therefore the diffusion coefficient back calculated from sampling structures is generally not an appropriate input for Life 365 A copy of NT BUILD 443 test can be requested from Nordtest via e mail nordtest vtt fi or the web http www vtt fi nordtest 84 Diffusion decay index m The chloride diffusion coefficient for concrete reduces over time when sufficient moisture is available for continued hydration Life 365 captures the effect of continued but diminishing hydration in Eq 2 by using the diffusion decay index m and assuming that hydration completes in 25 years after which point the diffusion coefficient stays constant at its computed 25 year value The diffusion coefficient must be obtained using NT BUILD 443 at several points in time to calculate m The value of m is the negative of the slope of the diffusion coeffici
82. gure 3 27 Life Cycle Costs Tab with Modify Uncertainty 50 Figure 3 28 Modify Uncertainty Panel zuo ws nte bot bs aw NR RIA 50 Figure 3 29 Default and Modified Steel Costs for Hybrid Epoxy Black Steel Slab 51 Figure 4 1 ASTM Estimate of Surface Chloride Concentration sess 54 Figure 2 New Life 305 Exposure Lab as sean ve eso Sud ER sate ueris 56 Figure 4 3 ASTM New Set Data Entry Panel eesseseeeeeeeneeeenen 56 AS M avandia 57 Figure 4 5 ASTM Panel with Data det pes cete eH emt 58 Figure 4 6 ASTM Panel ASTM Calculations Tab sese 59 4 Figure 4 7 Accessing an ASTM Dataset in Life 365 60 Figure 4 8 Life 365 ASTM Guidance Tab ca edi ees ere Fast rat cie tr to ea maces 61 Figure 4 9 Verification of Results for Levenberg Marquardt Algorithm 62 Figure 5 1 Components of Concrete Service Life sse 65 Figure 5 2 Chloride Levels by Region of North America 69 Figure 5 3 Effects of w om on Diffusion Coefficient sessione dept 71 Figure 5 4 Effects of Silica Fume on Diffusion Coefficient esses 72 Figure 5 5 Effects of Age on Diffusivity uii ense bea tea CQ UE ARD A URNA TH
83. he last of which is the observed value of concentration at depth x and time We instead use a Levenberg Marquardt nonlinear least squares 61 algorithm that will find the values of c and D The solver needs a gradient of this function in particular the first derivatives of c x t with respect to c and D These derivatives are c x t x 1 erf I and Eq 4 dc 7 v4Dt 1 2 iux x to eee end p i Eq 5 gp Ju 2 Implementing these in Life 365 our verification test is that this Levenberg Marquardt algorithm produces the same estimate of surface concentration and diffusion as those obtained from ASTM C1556 as illustrated in Figure 4 9 eoo ASTM C1556 Estimation of Max Surface Concentration Life 365 2 2 BETA FOR CONSORTIUM REVIEW Es Some Guidance Project Sets Graph Set Report Name double click to edit Max Conc Units Table 1 Results ASTM C1556 Dataset 0 605 wt conc Cs Ci Da t sum 0 605 0 085 4 86E 13 365 2 22E 3 Selected Set ASTM C1556 Dataset Table 2 Calculations Parameters x Measured Value Predicted Value Meas Pred Error 2 1 000 0 368 0 530 0 00E0 0 00E0 Sample Depth mm Conc wt conc 2 000 0 450 0 458 8 20E 3 6 72E 5 1 1 000 0 368 3 000 0 410 0 391 1 94E 2 3 76E 4 2 000 0 450 4 000 0 326 0 329 3 31E 3 1 10E 5 3 000 0 410 5 000 0 266 0 275 9 49E 3 9 01E 5 4 000 0 326 6 000 0 231 0 230 1 25E 3 1 5
84. ht and see Section 3 10 pg 45 of this manual for details on how to use service life uncertainty in your analysis For now leave the Compute uncertainty unchecked 33 Selected mixture This section lists the properties of the concrete mixture selected in the upper Define Concrete Mixtures panel and allows you to edit these properties To see the properties of any one of your concrete mixtures simply click the row of the mixture in this upper panel Mixture group use this section to set the water cementitious materials ratio w em of your concrete mixture and whether and to what level you are using SCMs Slag Class F fly ash or Silica fume Enter the SCM amounts in percent substitution Rebar and Inhibitors groups use these sections to select the type of reinforcing steel used in your structure Black steel Epoxy coated or 316 Stainless which affects the initiation period and propagation period of the concrete service life The Rebar vol concrete field is used to input the percent of the concrete that is steel this is used to calculate the cost of steel in your concrete structure where the costs of the steels are set in 1 the Individual Costs tab under the Default Concrete and Repair Costs tab and 2 the Default Settings and Parameters tab at the bottom of the Life 365 window Use the Inhibitor drop down to include in your mixture any corrosion inhibitors that will be used The units of measure of these i
85. igure 2 1 Examples of Concrete Surface History and Environmental Temperatures 11 Figure 2 2 Relationship Between Dog and W CM ssessssessssssssssseseesesseseesessersesseseesesseseese 12 Figure 2 3 Effect of Silica Fume on 13 Figure 2 4 Effects of Fly Ash and Slag on D sere arreter rris bes 14 Figure 2 5 Effects of Membranes and Scalers Lo oca peti ces 16 Figure 2 6 Limited Modeling of Diffusion in Slabs Deeper than 10 Inches 17 Figure 2 7 Single Quadrant m 2D Column esteso pi 19 Figure 2 8 Single Quadrant Variables in 2D Column eee 20 Figure 2 9 Life 365 ERF Comparison Over Depth at Time of Initiation 23 Figure 3 1 Windows Java settmgs Panel 2e mios ed REPAS NERIS I NNUS INS EIER 27 Figure 3 2 Determining Current Java Version in Mac OS X Terminal Console 28 Fig re 3 3 Start p Screech ne itu See SR eet udis eve 29 Figure 5 4 Project teet utt testas ettet anciana ut en e ng 30 Figure 3 5 Exposure Tab etes tei edens iei a dva 32 Figure 3 6 Concrete Mixtures Passes TOI ERI ae SE ASINI PIS 33 Pisure 3 4 Service lafe Fab eos oc oaa dev these e Ceo acia ua 35 Figure 3 8 Cross section Tab eerte eerte teneret eene rnnt tr een deese ike 35 Figure 3 9 Concrete Initiation Graphs sid s
86. in a simplified manner Life 365 assumes that both membranes and sealers only impact the rate of chloride build up and can only be reapplied up to the time of the first repair Membranes start with an efficiency of 100 percent which deteriorates over the lifetime of the membrane a lifetime of 20 years and no re applications This means that the rate of build up starts at zero and increases linearly to the same rate as that for an unprotected concrete at 20 years As shown in the left panel of Figure 2 5 surface chlorides for unprotected concrete labeled PC increases at a rate of 0 04 percent per annum and reaches a maximum concentration of 0 60 percent at 15 years In the right panel surface chlorides for concrete protected by a default membrane increase at a lower rate but then reach the same rate after 20 years The user can also set his own values for initial efficiency lifetime of the membrane and re applications 15 Effect of Membrane Effect of Sealer 0 8 0 8 g g 3 06 06 E s 5 5 B E 0 4 04 o o c t 8 Membrane 8 Sealer 8 02 9 02 g g E 2 7 0 0 0 5 10 15 20 25 30 0 5 10 15 20 25 30 Age years Age years Figure 2 5 Effects of Membranes and Sealers Sealers are dealt with in the same way except that the default lifetime is only 5 years The example in Figure 2 5 shows the effect of reapplying the sealer every 5 years Each time the sealer is applied the build up rate is rese
87. in the lower panel When the Use defaults button is not checked then the user must manually input these concentration and temperature values In Life 365 v2 2 the user can manually input their own maximum chloride level by also using values measured in accordance with ASTM C1556 see Section 4 for details Define Chloride Exposure The rate of buildup and maximum level of external chloride concentrations affect the rate of chloride ingress and ultimately concrete service life Use the following variables to set these rates and confirm them with the Surface Concentration graph on the right Max surface conc the maximum level of chloride buildup that the concrete structure will experience over its lifetime measured either in wt conc or base unit specific units i e either kg cub m SI metric or Ib cub yd US units Time to build to max yrs the number of years for the buildup to reach its maximum level It is assumed that the buildup is zero at the beginning of the structure s life and that it increases linearly 32 Define Temperature Cycle When the Use defaults box is not checked the user needs to input the annual temperature cycle to which the project is exposed these temperatures are part of the service life calculations that determine the effects of temperature on concrete diffusivity If the user selected either SI metric or Centimeter metric as the Base unit in the Project tab then the temperatures mus
88. ision to adopt a more simplified approach for Life 365 was based on making the model accessible to engineers as a design tool for a wide range of general applications Accounting for multi mechanistic transport in partially saturated concrete requires detailed knowledge of site specific conditions and a wide range of material properties that are not usually available to the engineer at the design stage It is envisaged that future versions of Life 365 will be more rigorous in the treatment of unsaturated flow without compromising the general applicability of the model 5 1 2 Propagation Period The propagation period defines the time necessary for sufficient corrosion to occur to cause an unacceptable level of damage to the structure or structural member under consideration The length of this period depends not only on the rate of the corrosion process but also on the definition of unacceptable damage This level of damage will vary depending on the requirements of the owner and the nature of the structure The corrosion rate will be influenced by a large number of factors including the nature of the embedded metal properties of the surrounding concrete and the composition of the pore solution within the concrete and the environmental conditions particularly temperature 66 and moisture availability Models have been developed to predict the corrosion rate and even the buildup of damage for example Martin Perez et al 1998 but
89. lso causes a reduction of the initial diffusion coefficient to 90 percent of the value predicted for the concrete without the admixture and decreases the rate of chloride build up at the surface by half in other words it takes twice as long for C to reach its maximum value These modifications are made to take account of the pore modifications induced by Rheocrete 222 which tend to reduce capillary effects i e sorptivity and diffusivity Miltenberger et al 1999 Miller and Miltenberger 2001 Effect of Stainless Steel In the current version of Life 365 it is assumed that grade 316 stainless steel has a corrosion threshold of C 0 50 percent i e ten times black steel This value was taken from the FHWA study conducted by MacDonald et al 1998 5 2 5 Propagation Period The propagation period used in Life 365 is t 6 years This value was selected on the basis of the studies of Weyers and others Weyers 1998 Weyers et al 1993 who determined that the length of the period between corrosion initiation and cracking varied in the range from 3 to 7 years for bridge decks in the U S A It is recognized that the rate of corrosion and hence the propagation period is a function of many parameters such as temperature moisture content and the quality of the concrete e g oxygen diffusivity and electrical resistivity It is envisaged that future versions of Life 365 will be able to account for changes in the value of on the ba
90. lve Fick s second law of diffusion using an apparent chloride diffusion coefficient to characterize the concrete under consideration A further assumption made is that the concrete that is completely saturated Although there are relatively simple numerical solutions to Fickean diffusion for saturated concrete many workers have chosen to implement Fick s law in a finite difference model to better facilitate changes in concrete properties and exposure conditions in space and time The chloride transport model used for analysis in Life 365 is an example of such a model and has been described in detail elsewhere Boddy et al 1999 This diffusion coefficient is corrected for time and temperature effects in Life 365 as explained in Section 2 1 under the assumption of uncracked concrete Clearly assuming that the concrete remains saturated and chloride ingress only occurs by ionic diffusion is an oversimplification Other models have been developed that account for unsaturated conditions and the effects of convective transport Saetta et al 1993 Martin P rez et al 1998 Indeed the chloride transport model within Life 365 known as Conflux developed by Evan Bentz of the University of Toronto is capable of dealing with combined diffusion and convection the latter resulting from either pressure or moisture gradients within the concrete Boddy et al 1999 These capabilities were not implemented within the current version of Life 365 The dec
91. n The geographic variation in North America is indicated in Figure 5 2 pg 69 Changes to k affect the time to reach Cmax Users can change k by changing the Time to build to max years field in the Exposure tab of the Computer Program or the sealer Initial efficiency field in the Concrete Mixtures tab Note that this estimation of the build up rate is separate from specification of the maximum surface chloride concentration the latter of which can be done in Life 365 through lookup tables ASTM C1556 or manual input The appropriate test protocol for determining the base build up rate for ordinary hydraulic cement concrete in a particular environment is 1 Obtain concrete powder samples from a representative specimen using a rotary drill and a bit with a diameter 1 5 times the maximum aggregate size 2 Obtain a minimum powder sample of 5 grams This mass can be obtained by carefully collecting the powder from a 5 to 10 mm deep hole 3 A minimum of 5 powder samples should be taken from the surface of a structure at each age 4 The total chloride content of the powder samples should be obtained in accordance with AASHTO T260 5 The initial chloride content should be subtracted from the total chloride measurement to obtain the adjusted surface chloride content 6 Record the mean and standard deviation of the adjusted surface chloride content for the structure 82 7 Repeat steps 1 through 6 at least 3 times during the first 5
92. n change the selection in the Base Units field and then press the Save button all future projects will use this new base unit When Life 365 starts in general your screen should look similar to Figure 3 3 This screen has two components on the left hand side there is a navigation menu under the Navigator section that lets you open new or existing Life 365 project files under the Settings section it lets you change the default settings and get help with particular screens and under the Tips section it displays text that gives you information and tips on using the software 28 eoo Life 365 v2 2 July 12 2013 Project Settings Navigator Open new project Open existing project Settings Help for this window Set default values About Life 365 Tips Lite 365 Life 365 Service Life Prediction Model for reinforced concrete exposed to chlorides EPOXY INTEREST GROUP Version 2 2 EUCLID CHEMICAL SLAG CEMENT ASSOCIATION Default Settings and Parameters Online Help Figure 3 3 Startup Screen There are also three tabs at the bottom of the screen 1 The Current Analysis tab which contains the current project on which you are working on startup this tab shows the opening banner in Figure 3 3 2 The Default Settings and Parameters tab which allows you to set the default values of parameters to be used in all projects see Section 3 9 1 p 34 and 3 The Online Help tab
93. n y 25 Ct wt conc In the Initiation Time Uncertainty panel the two Service Life Graphs graphs show the computed uncertainty in concrete mix design initiation times as computed by the methodology used in 15 0 Life 365 see the Users Manual for details When 12 5 comparing mixes in the left panel a mix that has a taller skinnier curve has less uncertaintyabout the service life while a mix with shorter wider curve has 0 more uncertainty about service life This tab is only enabled when the above Compute Uncertainty box is checked Base case Cross section Initiation Conc Characteristics Init Prob Init Variation Alternative 1 W Initiation Propagation Default Settings and Parameters Online Help Figure 3 6 Concrete Mixtures Tab Define Concrete Mixtures This section allows the user to input the concrete mixtures and corrosion protection strategies of each alternative Because the calculation of concrete service life is computationally intensive you need to press the Calculate service lives button after inputting the mixtures and strategies to make the calculations Check mark the Compute uncertainty box if you want Life 365 to compute the uncertainty of service life for each concrete mixture In general this is a calculation reserved for advanced users of Life 365 to understand Life 365 uncertainty analysis press the Help button to the rig
94. n from this data It then allows the user to use this estimate as the maximum chloride concentration used in the Exposure tab The user however still needs to input their own estimate of the time in years for this concentration to be reached The procedure also estimates a bulk diffusion coefficient for the concrete This estimate is based on Fick s Second Law based model NOT Life 3657 and thus is not used by Life 365 in its service life calculations For more information about the ASTM C1556 technique see the ASTM Publication of this standard test method as well as the Life 365 Users Manual Figure 4 8 Life 365 ASTM Guidance Tab 4 3 Software Algorithm The ASTM C1556 procedure requires an algorithm to fit the laboratory data to a diffusion and surface concentration curve that reflects Fick s second law of diffusion c x 1 2c c eoe t Eq 2 where x depth from the top surface t time since the exposure to the surface chlorides constant chloride concentration at the surface of the concrete c the constant ambient chloride concentration of the concrete and D the constant chloride diffusion coefficient of the concrete The specific requirement stated in ASTM C1556 is to select the values of and D that minimize the function i 2 bic c x t Eq 3 where the variables are and D and the parameters or the information taken as given in this equation are x t and c t
95. nce on Durability of Concrete Ed V M Malhotra ACI SP 171 American Concrete Institute Detroit Miller B D and Miltenberger M A 2001 The effects of corrosion inhibiting admixtures on chloride transport in concrete In Ion and Mass Transport in Cement Based Materials Ed Hooton et al American Ceramic Society Westerville OH pp 367 376 Miltenberger M Luciano J and Miller B 1999 Comparison of Chloride Diffusion Coefficient Tests for Concrete Proceedings of the 8 International Conference on Durability of Building Materials and Components National Research Council Canada Ottawa Nmai C K and McDonald D 1999 Long term Effectiveness of Corrosion Inhibiting Admixtures and Implications on the design of Durable Reinforced Concrete Structures A Laboratory Investigation RILEM International Symposium on The Role of Admixtures in High Performance Concrete Monterrey Mexico NTBuild 1995 NordTest Method for Accelerated Chloride Penetration Into Hardened Concrete NTBuild 443 Pun P 1997 Influence of Silica Fume on Chloride Resistance of Concrete M A Sc Thesis University of Toronto Pyc W A Weyers R E Sprinkel M M Weyers R M Mokarem D W and Dillard J G 2000 Performance of Epoxy Coated Reinforcing Steel Concrete International Vol 22 2 pp 57 64 Rushing Amy S and Fuller Sieglinde K Energy Price Indices and Discount Factors for Life Cycle Cost Analysi
96. ncertainty analysis uncheck the Compute uncertainty box in the Concrete Mixes tab Do you want to compute uncertainty Yes Figure 3 22 Service Life Uncertainty Prompt Initiation Period Probabilities When the Yes button is pressed and then the Recalculate service lives button the uncertainty in service life is computed for each concrete mixture listed in the Concrete Mixtures tab and the Initiation Time Uncertainty panel in this tab is activated These graphs are both important but relatively difficult to interpret to give the necessary tools to interpret these graphs let s examine in detail the two figures more closely Service Life Graphs Service Life Cross section Initiation Conc Characteristics Init Variation Initiation Period Probability by Year Cumulative Initiation Per Prob by Year 75 75 Year Year Base case Alternative 1 Base case Alternative 1 Figure 3 23 Initiation Probability Graphs Consider the two alternatives shown in Figure 3 24 The Base case the red line is from a basic mixture with no additives or corrosion protection strategies such as silica fume fly ash inhibitors membranes or sealants Alternative 1 the blue line has added inhibitors Based on the best guess values in the project windows the Base case has a calculated initiation period of 10 years and Alternative 1 an initiation period of
97. nhibitors are either I cub m liters per cubic meter or gal cub yd gallons per cubic yard depending on the Base unit selected in the Project tab Barriers group use this section to include a membrane or sealant application on the concrete If the Use defaults box is checked then you simply select membrane or sealant if not checked then you must input the values of Initial efficiency 7o Age at failure yrs and times reapplied for the particular one selected Custom Mixture Properties In addition to inputting the constituent physical concrete mixture and other corrosion protection strategies Life 365 allows the user to input directly the model properties used to calculate service life Doing so will potentially generate results that override one or more of the basic Life 365 modeling assumptions so check marking the Custom button the first time will cause a pop up window to appear asking that the user confirm he is aware of this The set of Custom input fields together override the model in the following ways Initial diffusion coefficient D28 Inputting the initial diffusion coefficient directly overrides the calculation of D28 based on w cm ratio and the level of silica fume Diffusion decay index m Inputting this index directly overrides the calculation of m based on the levels of slag and fly ash The value of m however must still be between 0 2 and 0 6 Hydration years By default Life 365 models hydration t
98. nship Between D2 and w cm It should be noted that these relationships pertain to concrete produced with aggregates of normal density and may not be appropriate for lightweight concrete Effect of Silica Fume The addition of silica fume is known to produce significant reductions in the permeability and diffusivity of concrete Life 365 applies a reduction factor to the value calculated for portland cement Dpc based on the level of silica fume 6SF in the concrete The following relationship which is again based on bulk diffusion data is used Dy Daen Eq 7 The relationship is only valid up to replacement levels of 15 percent silica fume The model will not compute diffusion values or make service life predictions for higher levels of silica fume 12 Effect of Silica Fume 1 0 8 Q E 06 o Qa Q 04 0 2 0 0 5 10 15 Silica Fume Figure 2 3 Effect of Silica Fume on Dsr Life 365 assumes that silica fume has no effect on either C or m Effect of Fly Ash and Slag Neither fly ash nor slag are assumed to effect the early age diffusion coefficient D s or the chloride threshold However both materials impact the rate of reduction in diffusivity and hence the value of m The following equation is used to modify m based on the level of fly ash F A or slag SG in the mixture m 0 2 0 4 50 SG 70 Eq 8 The relationship is only valid up to replacement levels of 50 pe
99. ons database and are expressed in either Celsius or Farenheit depending on the Base units selected in the Project tab If the box is not checked be sure to input monthly temperatures that reflect condtions at your project location Last channad Sentemher 7 2009 Exposure Conditions Default Settings and Parameters Online Help Back to Analysis Current Analysis Figure 3 20 Online Help Individual pages can be accessed by selecting from the drop down box at the bottom of the panel in Figure 3 20 this box displays Concrete Mixtures If instead you are working on a particular window say the Project tab and you want to access the help page for that window simply go to the left hand navigation panel and select Help for this window from the Settings section where available a help window will display with information for the help you need 3 10 The analysis described in Section 3 2 through Section 3 8 is in and of itself generally sufficient it calculates service life and life cycle cost given the best guess estimates of economic conditions environmental conditions concrete mixture values and economic costs inputted by the user Advanced Analysis Service Life Uncertainty There may be however uncertainty about some of these conditions for example what the interest rates will be over the study period what temperature fluctuations will be what the effects of concrete admixtures are on the st
100. ons it is exposed to in service To improve the reliability of the estimate core samples should be taken from Section 7 of ASTM C1556 11 2011 Method calls for An aqueous NaCl solution prepared with a concentration of 165 1 g NaCl per L of solution 54 similar types of structures in the same type of exposure anticipated for new construction for example parking garage structures marine exposure etc 4 2 How Life 365 Uses the ASTM C1556 Method Life 365 uses two types of exposure conditions surface chloride concentration that build up over time and monthly average temperatures to capture how the environment affects the corrosion initiation period The surface chloride concentration over time is modeled as a constant initial maximum concentration with a linear increase to that maximum from time zero The defaults estimates of maximum chloride concentration are based on data from the Salt Institute and the time to buildup to maximum are based on data in Weyers 1993 Life 365 now also includes a module that uses measurements obtained using ASTM C1556 for generating an estimate of the maximum surface chloride concentration and the time to build t up to that maximum 4 2 1 Data Required for Maximum Surface Concentration Calculations When creating a new ASTM C1556 concrete sample data set the analyst needs to have the following inputs or required data The concrete chloride concentration by depth of
101. ow Let s say that the cost of epoxy coated steel is 2 93 and the cost of black steel is 2 20 these costs are shown in the left panel of Figure 3 29 If approximately 1 2 of the steel in the hybrid epoxy black steel slab is epoxy then the average cost of steel is 2 93 2 20 2 2 57 Ib We can input then this average price in the Epoxy coated stl box as shown in the right panel of Figure 3 29 and Life 365 will use this average price for all slabs that use Epoxy coated steel on top and black steel on the bottom Concrete amp Steel Concrete amp Steel Concrete cub yd 76 46 Concrete cub yd 76 46 Black stl S Ib 2 20 Black stl S Ib 2 20 Epoxy coated stl Ib 2 93 Epoxy coated stl Ib 2 57 Stainless stl 5 6 14 55 Stainless stl Ib 14 55 Default Costs Hybrid Costs Figure 3 29 Default and Modified Steel Costs for Hybrid Epoxy Black Steel Slab Note for this averaging to work you must use this hybrid epoxy black set of steels for all alternative mixtures you specify that have epoxy coated steel as the top layer At this time Life 365 has no information on the extension of service life obtained with the 51 hybrid epoxy black set of steel reinforcing It is obviously less than the 20 years built into the program for all epoxy coated steel Finally according to one report Concrete Reinforcing Steel Institute 1998 this hybrid steel set has an effective propagation period of 15 y
102. pply barriers Loc New York NEW YORK Type Parking garages Max surface 0 800 wt conc Years to buildup 7 4 slabs and walls 1 D should they be in the mix and Outer dim 30in clear cover 2in 3 the cost to repair the concrete The Construction Cost is the sum of the basic concrete mix plus the costs of reinforcing SCMs and inhibitors The Barrier Cost is Concrete Mixes Alt name User Reinf the cost of applying a Base case 0 42 Black Steel membrane or sealer to the surface area of the structure Alternative 1 3 Black Steel The Repair Cost is the cost of repairing the structure starting when the service life of the concrete is reached it first occurs after the estimated service life and then repeats at fixed intervals 101 Eee Settings and Parameters Online Help Figure 3 16 Service Life SL Report Tab 42 eoo Life 365 v2 2 new project July 12 2013 Project Settings Current Project Save project Save project as fO 1 QQ 164 05 Export project data Close project Project Exposure Concrete Mixtures Individual Costs Life Cycle Cost Service Life Report Report Steps Berne Life 365 v2 2 Life Cycle Costs Define alternatives Define exposure Define mix designs Project New Project Description Default settings for a new project Compute ser
103. r can input temperature profile relevant to the location in terms of monthly average temperatures in either degrees Celsius if the project is using SI units or degrees Fahrenheit if the project is using US units Base Case Concrete Mixture The base case concrete mixture assumed by the model is plain portland cement concrete with no special corrosion protection strategy For the base case the following values are assumed Dog 1 1001206 240 weters squared per second m s Eq 4 11 0 20 Eq 5 0 05 percent wt of concrete Eq 6 The relationship between D s and the water cementitious materials ratio w cm is based on a large database of bulk diffusion tests The nature of the relationship is shown in Figure 2 2 corrected to 20 C The value of m is based on data from the University of Toronto and other published data and decreases the diffusion coefficient over the course of 25 years after which point Life 365 holds it constant at the 25 year value to reflect the assumption that hydration is complete The value of C is commonly used for service life prediction purposes and is close to a value of 0 40 percent chloride based on the mass of cementitious materials for a typical concrete mixture used in reinforced concrete structures Relationship Between D 2 and W CM 1E 10 1E 11 Diffusion Coefficient D 28 m s 1E 12 0 3 0 4 0 5 0 6 W CM Figure 2 2 Relatio
104. rcent fly ash or 70 percent slag and m itself cannot exceed 0 60 which would occur if fly ash and slag were used at these maximum levels that is m must satisfy m lt 0 60 Life 365 will not compute diffusion values or make service life predictions for higher levels of these materials and after 25 years holds the diffusion constant at the 25 year value to reflect that hydration is complete Figure 2 4 shows the effect of m for three mixtures with w cm 0 40 and with plain portland cement PC 30 percent slag and 40 percent fly ash Table 1 lists these mixture proportions and their computed the diffusion coefficients for 28 days 10 years and 25 years For years greater than 25 Life 365 uses the computed 25 year diffusion coefficient 13 Effect of Fly Ash and Slag T a E amp c o 5 a 40 FA Figure 2 4 Effects of Fly Ash and Slag on D Table 1 Effects of Slag and Fly Ash on Diffusion Coefficients m Dos Doasy lt 0 60 x 10 m s x 1073 m s x 10 m s PC 0 20 79 30 25 30 percent SG 0 37 79 13 9 3 40 percent FA 0 52 79 6 3 3 9 Effect of Corrosion Inhibitors The model accounts for two chemical corrosion inhibitors with documented performance calcium nitrite inhibitor CNI and Rheocrete 222 a proprietary product from Master Builders in the Life 365 software it is referred to as A amp E for amines and esters It is intended that other type
105. rces of Initiation Period Uncertainty To understand how the concrete mixture factors influence the uncertainty in initiation period the Service Life Results section also includes an Init Variation graph shown in Figure 3 26 This graph shows by alternative the level of uncertainty in each initiation period and the components of this uncertainty For example in the figure Alternative 1 has much higher uncertainty than the Base case and this uncertainty is primarily due to m which represents the effects of hydration on decreases in concrete diffusivity followed by uncertainties in cover depth and D28 Service Life Graphs Service Life Cross section Initiation Conc Characteristics Init Prob Init Variation Initiation Variation Base case Alternative 1 m D28 8 Max Cs Ct Cover depth Figure 3 26 Initiation Variation Graph While the red line is below the blue line over the 5 to 8 year range the probabilities of these values occurring are small Technically we need to use the calculation of second order statistical dominance to determine if in fact Alternative 1 has the longest initiation period in a probabilistic sense but in this example case we can draw this conclusion from examination of the graph 49 Impacts on Life Cycle Costs In cases where there is not clear statistical dominance of one service life over the other s for example when there are many alternatives and the CDF line
106. result estimates the average diffusion coefficient over say the 15 year life of a concrete field sample as opposed to the instantaneous diffusion coefficient in the 15 year 4 1 2 Maximum Surface Concentration In addition to estimating average diffusion coefficients ASTM C1566 can be used to estimate the maximum surface concentration of chlorides to which the concrete has been exposed to over its lifetime Figure 4 1 illustrates how the ASTM method directly estimates the average surface chloride concentration as the intersection of the Fick s second law based grey line and the horizontal access that is the estimated chloride concentration at depth 0 the blue dot in the figure 6 e Concentration 9 owt conc m 2 5 5 0 7 5 10 0 12 5 15 0 17 5 20 0 22 5 25 0 Depth mm Figure 4 1 ASTM Estimate of Surface Chloride Concentration When ASTM C1556 is performed on standard molded samples prepared and conditioned in a controlled laboratory environment this surface concentration is known exactly For in situ core sampling and other chloride concentration tests however the value of this surface concentration is unknown and this input is needed by Life 365 This provides better input information than the default values of Life 365 This update to Life 365 ASTM C1556 module allows for the input of a better estimate a maximum surface chloride concentration of a structure for the typical exposure conditi
107. rrosion inhibitors type of steel and coatings and type and properties of membranes or sealers From these input parameters the model selects the necessary coefficients for calculating the time to corrosion as detailed above Surface Chloride Build Up The model determines a maximum surface chloride concentration and the time taken to reach that maximum fax based on the type of structure its geographic location and exposure as input by the user For example if the user selects a bridge deck in an urban area of Moline Illinois the model will use the surface concentration profile shown in the left panel of Figure 2 1 Alternatively the user can input his own profile in terms of maximum surface concentration and the time in years to reach that maximum Life 365 v2 2 includes the additional ability to input a maximum surface concentration based on ASTM C1556 data calculations Surface History Total Annual Temp History 05 a4 a3 a2 0 1 Surface Conc conc Temperature deg C yews Marth Number Figure 2 1 Examples of Concrete Surface History and Environmental Temperatures Temperature Profile The model determines yearly temperature profiles based on the user s input for geographical location using a database compiled from meteorological data For example if the user selects Moline Illinois the model will use the temperature profile in the right panel in Figure 2 1 Alternatively the use
108. rt Location New York Exposure Parking garages _ Set values manually below Chloride Exposure automatically set Max Concentration Surface Concentration Define mix designs 0 96 wt conc 0 8 Compute service life 0 7 Define project costs wt conc Compute life cycle cost t 805 Settings 204 Help for this window t Mi Set default values to build to max surface concentratior 2 About Life 365 0 2 Tips 0 1 0 0 This window is used to make basic documentation 0 10 20 30 40 50 60 70 80 such as analysis name and Year date to set economic parameters such as inflation rate and discount rate see the Help section for 90 100 110 120 130 140 150 Temperature Cycle automatically set Temperature History Monthly Temperatures T 80 definitions of these terms and to select the number Li 701 and descriptions of February Ti 60 alternatives to be analyzed 50 a E 40 5 30 20 101 0 0 1 2 4 5 6 7 8 9 10 11 12 Month Default Settings and Parameters Online Help Figure 3 5 Exposure Tab Select Location When the Use defaults box is checked you can select a Location Sub location and Exposure that closely matches the conditions of your project and Life 365 will use its database of locations to estimate the Max surface conc of chlorides and Time to build to max in the upper panel and the Temperature History
109. ructure s service life and what repair costs will be over the study period Many of these uncertainties can be addressed 45 through sensitivity analysis of which the Sensitivity Analysis tab Figure 3 15 is an example Formal uncertainty analysis would include many of the above parameters and procedures Model of Initiation Period Uncertainty To help understand the impact of uncertainty about a number of the input parameters on the initiation period and thus concrete service life Life 365 comes included with a formal method for estimating the uncertainty of a concrete mixture s service life Based on Bentz 2003 and the formulas in Chapter 2 it varies the following parameters in these formulas to estimate the probability density function of initiation period of the concrete mixture design e the diffusion rate at 28 days D28 the diffusion decay index m the maximum surface chloride level C the chloride threshold to initiate corrosion of steel C and the clear cover to reinforcement The resulting probability and cumulative probability density functions are used in Life 365 to calculate the effects of initiation period uncertainty only on life cycle cost As shown in Figure 3 21 the user activates Life 365 to compute initiation period uncertainty by checking the Compute uncertainty box in the upper part of the Concrete Mixtures tab Project Exposure Concrete Mixtures Individual Costs Life Cycle
110. s NISTIR 85 3273 18 Gaithersburg MD National Institute of Standards and Technology November 2012 Saetta A Scotta R and Vitaliani R 1993 Analysis of chloride diffusion into partially saturated concrete ACI Materials Journal Vol 90 5 pp 441 451 Sandberg P Recent Studies of Chloride Ingress in Uncracked Marine Concrete at various Exposure times and Elevations Report TVBM 3080 Lund University Lund Institute of Technology Division of Building Materials 79 Sandberg P and Tang L 1994 A Field Study of the Penetration of Chlorides and Other Ions into a High Quality Concrete Marine Bridge Column Concrete Durability Ed V M Malhotra ACI SP 145 American Concrete Institute Detroit pp 557 571 Sandberg P Pettersson K and Jorgensen O 1996 Field Studies of Chloride Transport into High Performance Concrete Performance of Concrete in a Marine Environment ACI SP 163 American Concrete Institute Detroit pp 233 254 Sherman M R McDonald D B and Pfeifer D W 1996 Durability Aspects of Precast Prestressed Concrete Part 2 Chloride Permeability Study PCI Journal Vol 41 4 Stanish K 2000 Predicting the Diffusion Coefficient of Concrete from Mix Parameters University of Toronto Report Steen P E 1995 Chloride Penetration in Marine Environment Part 2 Results from Field Test on Coastal Bridges in Norway Proceedings of the Nordic Seminar in Lund Corrosion
111. s cross each other over different years we can still calculate the effects of different outcomes of initiation periods and thus service lives on life cycle cost using the following technique when conducting service life probabilistic analysis a new Modify Uncertainty panel appears in the lower portion of the Life Cycle Cost Life Cycle Cost tab Figure 27 and Figure 3 28 eoo Life 365 v2 2 new project July 12 2013 Project Settings Current Project Serene Project Exposure Concrete Mixtures Individual Costs Service Life Report LCC Report Save project Save project as Display Life Cycle Cost Export project data ae a Show results as _ totals unit costs Structure Dimension 10 000 sq ft Steps Timelines Sensitivity Analysis Define project Table Define alternatives Define exposure Name Construction Cost Barrier Cost Repair Cost Life Cycle Cost Define mix designs Base case 13 63 0 00 38 93 52 55 Compute service life Alternative 1 13 63 0 00 38 47 52 10 Define project costs Compute life cycle cost Settings Help for this window Set default values Graphs About Life 365 Life Cycle Cost by Alternative Tips This window displays the i computed life cycle cost of w each alternative 52 55 sq ft WI Alt Component Costs 3 10
112. s of inhibitors can be included in the model when appropriate documentation of their performance becomes available Ten dosage levels of 30 percent solution calcium nitrite are permitted in Life 365 The inclusion of is assumed to have no effect on the diffusion coefficient D s or the diffusion decay coefficient m The effect of on the chloride threshold C varies with dose as shown in the following table 14 Table 2 Effects of CNI on Threshold CNI Dose Threshold C wt conc litresim gal cy 0 0 0 05 10 2 0 15 15 3 0 24 20 4 0 32 25 5 0 37 30 6 0 40 In addition a single dose of Rheocrete 222 or amines and esters as it is referred to in the software is permitted in the model the dose is 5 litres m concrete This dose of the admixture is assumed to modify the corrosion threshold to C 0 12 percent by mass of concrete Furthermore it is also assumed that the initial diffusion coefficient is reduced to 90 percent of the value predicted for the concrete without the admixture and that the rate of chloride build up at the surface is decreased by half in other words it takes twice as long for to reach its maximum value These modifications are made to take account of the pore modifications induced by Rheocrete 222 or amines and esters which tend to reduce capillary effects 1 e sorptivity and diffusivity Effect of Membranes and Sealers Membranes and sealers are dealt with
113. second law is the governing differential equation 2 acy PC dt dx where the chloride content D the apparent diffusion coefficient x the depth from the exposed surface and t time The chloride diffusion coefficient is a function of both time and temperature and Life 365 uses the following relationship to account for time dependent changes in diffusion t m D t D Eq 2 where D t diffusion coefficient at time t Dref diffusion coefficient at time tef 28 days in Life 365 and m diffusion decay index a constant Life 365 selects values of and m based on the details of the composition of the concrete mixture 1 water cementitious material ratio w cm and the type and proportion of cementitious materials input by the user In order to prevent the diffusion coefficient from continually decreasing with time the relationship shown in Eq 2 is assumed to be only valid up to 25 years beyond which D t stays constant at the D 25 years value Life 365 uses the following relationship to account for temperature dependent changes in diffusion Uu 1 DP D exp gt Eq 3 ref p R gt q where D T diffusion coefficient at time t and temperature T Dref diffusion coefficient at time t e and temperature 7 U activation energy of the diffusion process 35000 J mol R gas constant and T absolute temperature In the model 28 days and
114. sis of environmental and material properties 7 n the software Rheocrete 222 is referred to as A amp E for amines and esters 76 Effect of Epoxy Coated Steel The use of epoxy coated steel is a commonly used corrosion protection strategy in North America The performance of epoxy coatings in protecting steel from corrosion is varied Manning 1996 Weyers et al 1998 Pyc et al 2000 and depends on a wide range of parameters MacDonald et al 1998 Based on extrapolations from accelerated laboratory data MacDonald et al 1998 predicted that epoxy coated top bars might be expected to extend the estimated time to corrosion from between 12 to 19 years A full treatment of the published data on the efficacy of epoxy coated bars is beyond the scope of this manual In Life 365 the propagation period is extended to t 20 years when epoxy coated reinforcement is selected However this is just a somewhat arbitrarily selected default value and the user is strongly encouraged to change this value based on local experience Also the user may consider modifying the repair frequency when epoxy coated bars are used 5 2 6 Temperature The temperature profiles for different geographic regions were compiled using data collected from the World Meteorological Organization 1961 1990 Global Climatic Normals Database 5 3 Input Parameters for Calculating Life cycle cost All the input parameters related to calculating the initial
115. st most but not all of the parameters used in your analysis your life file contains all of the parameters used Each report can be printed by pressing the printer icon in the upper left corner of the window If you want to save the report as a PDF file click on the disk drive icon in the upper left corner select pdf as the filetype enter a file name and save eoo Life 365 v2 2 new project July 12 2013 Project Settings Project Exposure Concrete Mixtures Individual Costs Life Cycle Cost LCC Report Save project Save project as Export project data Close project MBO DOD AA 60 62 Steps Define project Define alternatives Define exposure Define mix designs Compute service life Life 365 v2 2 Concrete Mixes and Service Lives Define project costs Compute life cycle cost Settings Help for this window Set default values About Life 365 Tips Project New Project Analyst Analyst Depth modeled 10 00 2 00 Description Default settings for a new project Date 07 12 2013 Surface Concentration Monthly Temperatures This tab shows the consituent Costs used to estimate life cycle cost in MEE EE o o y 075 30 00 8 050 0251 o o 0 00 The costs of each alternative 0 25 50 75 100 125 150 50 75 100 are 1 the base cost of Year Month installing the concrete itself 2 the cost to a
116. stl Ib 0 45 Sealer sq ft 0 65 Area to repair X 10 0056 Epoxy coated stl Ib 0 60 Inhibitor 5 gal 5 68 Fixed repair interval yrs 10 Stainless stl S Ib 2 99 Set as defaults Figure 3 12 Default Concrete and Repair Costs Costs for Each Alternative Mix Design Based on these costs the Project Costs section lists up to three costs 1 the Construction cost or cost of mixing placing the concrete 2 the Barrier cost or the cost of applying a membrane or sealer and 3 the Repair cost or the cost of repairing the concrete over the study period Use the Select Alternative drop down box to select which alternative you want to view in this panel as well as in the Cost Time line for Alternative graph below Cost Timeline This section shows a time line of the project costs The graph in Figure 3 11 shows in particular the initial construction cost occurring between year 0 and year 1 and then the repair costs starting after construction as indicated by the red arrow and continuing every 10 years as indicated by the vertical gray lines within the white box until year 75 Use the Select Alternative drop down box above to see the different cost timelines of your different alternative mixtures 3 7 Life Cycle Cost Tab Once the project exposure concrete mixtures and individual costs data have been entered the resulting life cycle cost of the alternative mixtures are computed and can be viewed and compare
117. t analysis LCCA is being used more and more frequently for this purpose Life 365 LCCA uses estimated initial construction costs protection costs and future repair costs to compute the costs over the design life of the structure Many concrete protection strategies may reduce future repair costs by reducing the extent of future repairs or by extending the time between repairs Thus even though the implementation of a protection strategy may increase initial construction costs it may still reduce life cycle cost by lowering future repair costs A number of models for predicting the service life of concrete structures exposed to chloride environments or for estimating life cycle cost of different corrosion protection strategies have been developed and some of these are available on a commercial basis The approaches adopted by the different models vary considerably and consequently there can be significant variances between the solutions produced by individual models This caused some concern among the engineering community in the 1990s and in response in May 1998 the Strategic Development Council SDC of the American Concrete Institute ACI identified the need to develop a standard model and recommended that a workshop be held to investigate potential solutions In November 1998 such a workshop entitled Models for Predicting Service Life and Life Cycle Cost of Steel Reinforced Concrete was sponsored by the National Institute of Standards and
118. t be input in degrees Celsius if the user selected US units as the base unit then temperatures must be input in degrees Fahrenheit 3 5 Concrete Mixtures Tab The Concrete Mixtures tab Figure 3 6 is used to define the concrete mixtures for each project alternative defined in the Project tab eoo Life 365 v2 2 new project July 12 2013 Project Settings It Pi t ERE Project Exposure Individual Costs Life Cycle Cost Service Life Report LCC Report Save project Save project as Export project data Type slabs and walls 1 D Calculate service life Compute uncertainty Close project e Steps Define Concrete Mixtures select a mix to edit its properties Det Name User Defined D28 in in sec m Ct wt conc Init yrs Prop yrs Service Life yrs Init P project Base case no 1 3751E 8 0 20 0 050 6 1 6 0 12 Define ee Alternative 1 no 7 0849E 9 0 20 0 050 9 8 6 0 15 8 Define mix designs lected mixture Alternative 1 A project that uses the a new mix of concrete Compute service life Mixture Rebar Barriers Define project costs x Compute life cycle cost wicm 0 30 Rebar steel type Black Steel lt none gt Rebar vol concrete 1 20 Settings Class F fly ash 0 0056 Help for this window Slag 9 0 00 inhibitor Set default values About Life 365 Silica fume 9 0 00 none Tips Custom 028 in in sec 7 T 0 2 Hydratio
119. t due to the continued hydration of the concrete see Eq 2 and Eq 8 It is either default value set by Life 365 on the basis of concrete mixture proportions provided by the user or inputted directly by the user in the Set own concrete properties section of the Concrete Mixtures tab In all cases Life 365 assumes that hydration of cementitious materials is complete after 25 years at which point the time varying effects of m no longer apply and Life 365 holds the diffusion coefficient constant Chloride threshold kg m Ib yd is the same units as C This is the concentration of chloride required to initiate corrosion of the embedded steel reinforcement The value is either a default value set by Life 365 The value changes based the basis of the type and quantity of corrosion inhibitor and the nature of the reinforcement Alternatively the user can input a different value in the Set own concrete properties section of the Concrete Mixtures tab Propagation period years This is the time taken for the corrosion process to cause sufficient damage to warrant repair The value is either a default value set by Life 365 on the basis of the type of reinforcement or inputted directly by the user in the Set own concrete 67 properties section of the Concrete Mixtures tab T Temperature C F The annual temperature profile is selected by Life 365 on the basis of the geographical location chosen by the user or a profile with month
120. t to zero and then allowed to build up back to the unprotected rate 0 04 percent per annum in the example at the selected lifetime of the sealer 5 years in the example Effect of Epoxy Coated Steel The presence of epoxy coated steel does not affect the rate of chloride ingress in concrete nor would it be expected to impact the chloride threshold of the steel at areas where the steel is unprotected Consequently the use of epoxy coated steel does not influence the initiation period However it is assumed in the model that the rate of damage build up is lower when epoxy coated steel is present and these effects are dealt with by increasing the propagation period from 6 years to 20 years Effect of Stainless Steel In the current version of Life 365 it is assumed that grade 316 stainless steel has a corrosion threshold of C 0 50 percent 1 e ten times the black steel C of 0 05 percent 2 1 3 Initiation Period Fickian Solution Procedures The Life 365 Computer Program uses a finite difference implementation of Fick s second law the general advection dispersion equation Implicit in the model are the following assumptions The material under consideration is homogeneous e g no surface effects The surface concentration of chlorides around the concrete member is constant for any given point in time The properties of the elements are constant during each time step calculated at the start of each time
121. tant depending on mixture proportions Bamforth 1999 recently proposed the values in Table 6 for m based on a review of published diffusion coefficients from more than 30 sources Table 6 Values of m Various Concrete Mixtures Concrete Mixture 0 264 Fly Ash Concrete 0 700 Slag cement Concrete 0 620 These values are based on published information mainly from marine studies It is felt that the rate of decay in marine conditions where there is a constant supply of moisture in most cases may be somewhat higher than in bridges and parking structures where the continued hydration reactions may be decreased by the reduced moisture availability Furthermore Bamforth gives no indication as to how the value of m will change with the level of fly ash and slag Many of the studies referred to by Bamforth were based on relatively high levels of fly ash e g 30 to 50 percent and slag cement e g 50 to 70 percent Thus it was decided to adopt a more conservative approach in Life 365 and allow the value of m to vary in the range 0 20 to 0 60 based on the level of fly ash FA or slag cement SG in the mixture The relationship used is m 0 2 0 4 FA 50 SG 70 Other researchers have proposed relationships between m and other parameters such as the w cm ratio and silica fume content of the mixture Mangat and Molloy 1994 Maage et al 1995 These are not considered in the current version of Life 365 but may
122. temperatures Life 365 accounts for time and temperature effects using the relationships in Eq 2 and Eq 3 For example the calculated diffusion coefficient at 10 years for a portland cement concrete with w cm 0 40 is 2 5 x 10 m s at 10 C This is not inconsistent with the range of values presented by Weyers 1998 Effects of Supplementary Cementitious Materials Besides the w cm the composition of cementitious materials also makes a significant impact to the diffusion coefficient of concrete Effect of Silica Fume The effect of silica fume on the early age diffusion coefficient of concrete was also determined using bulk diffusion data from the University of Toronto and various published sources Figure 5 4 shows the relationship between silica fume content and the diffusion coefficient The graph shows the ratio of the diffusion coefficient with silica fume Dsr to the control mixture without silica fume Dpc 71 _ 0 16465 D s D pce 2 Sherman et al 1996 r 0 6987 A McGrath and Hooton 1997 Stanish 2000 o Pun 1997 DsF D Pc Titherington 1998 o Sandberg 1998 Sandberg et al 1996 O Gjorv et al 1994 SF 96 Figure 5 4 Effects of Silica Fume on Diffusion Coefficient Effect of Slag Cement and Fly Ash Results showing the effect of slag cement and fly ash on the early age diffusion coefficient of concrete are inconclusive various data show that these materials can either
123. tential measurements 3 At the first sign of corrosion activity obtain the chloride content at the reinforcing steel level in the companion unreinforced specimen Corrosion activity is indicated by 1 a sharp reduction in half cell potential 2 the presence of a macrocell current and or 3 a sharp reduction in the polarization resistance 4 Verify corrosion visually and determine the chloride content at the reinforcement level in the reinforced specimen when an integrated macrocell current of 75 coulombs is obtained Stable corrosion activity is typically present at this point 5 If corrosion exists only under the end treatment the chloride content measurements from the pair of specimens is discarded 6 If more than 95 percent of the visual corrosion exists in the exposed section the chloride threshold value can be calculated as the average of the adjusted chloride contents determined from the pair of specimens In the absence of crevice corrosion under the end treatment the chloride threshold value is determined by the average of the six chloride content measurements 85 The important factors to consider when evaluating chloride threshold test results 1 Electrically accelerated tests change the environment adjacent to the reinforcing steel and can provide erroneous results 2 Galvanic corrosion can contribute to premature failures 3 Bar preparation prior to casting specimens can influence the test results Bar prepar
124. ternit 36 Figure 3 10 Concrete Characteristics Dp iS RUD ede et 36 Figure 3 11 Individual Costs iusso aen eum ba atn Itam Nau ias euh 37 Figure 3 12 Default Concrete and Repair Costs queis dun 38 Figure 5 13 Life Cycle Cost deer restent ren redet eo rdi arate 39 Figure 3 14 Life Cycle Cost Timelines Tab uoces de oi acts tris rr t es eS a 40 Figure 3 15 Life Cycle Cost Sensitivity Analysis Tab eee 4 Figure 3 16 Service Life SD Report iita er eie i eterne e soi ein 42 Figures A7 ECC Report abs qusc eeu 43 Figure 3 18 Pop up Menu for Copying a Graph to 44 Figure 3 19 Default Settings and Parameters Tab sse 44 Figure 3 20 Online Help Jaco i aig NR SPORE Ue 45 Figure 3 21 Concrete Mixtures Tab Initiation Time Uncertainty 46 Figure 3 22 Service Life Uncertainty Prompt dose eoe ette e Dua eet e ede Hagan 47 Figure 3 23 Initiation Probability QYaplisc seio repe obo e es 47 Figure 3 24 Initiation Period Probability by Year sse 48 Figure 3 25 Cumulative Initiation Per Prob by Year sss 48 Figure 3 26 Initiation Variation Graph tans ces poer ie a ue 49 Fi
125. the cost of concrete only without inhibitors barriers or steel these costs are all used later when calculating the initial construction cost If however a particular mixture uses for example SCMs or other materials that cause concrete costs to be different than the default cost enter that cost in this table by double clicking on the cost itself doing so will cause the User box to be check marked If you enter a cost and need to return that cost to the default cost simply uncheck the User box 37 Default Concrete and Repair Costs This section Figure 3 12 lists the costs associated with three categories of project costs Concrete amp Steel Barriers amp Inhib and Repairs When you first start your project Life 365 uses the default values of these costs listed in the Default Settings and Parameters tab located at the bottom of the Life 365 screen These are converted when necessary from the units of measure listed in this tab to the units used in your project If you save your project and access it later it will list again your project values of cost If you would like to make the values currently shown in this project to be the default values for all future projects press the Set as defaults button Concrete and Repair Unit Costs Set Concrete Costs Concrete amp Steel Barriers amp Inhib Repairs Concrete cub yd 76 46 Memb sq ft 3 07 Repair sq ft 37 16 Black
126. the sub location closest to your project Based on the selections made in the Location and Sub location boxes this will list the types of exposure Select the type of exposure appropriate for your structure Your selection here will determine the maximum chloride exposure to which your structure will be exposed and the rate to that exposure If you want to print this Exposure window press the Print button at the bottom of the page This is the maximum level of chloride to which your structure will be exposed When using the default locations this value is retrieved from the database of exposure conditions otherwise the user must specify them Maximum surface concentration can be specified in either wt of conc or units specific measures either Ib cub yd or kg cub m Max surface conc Define Chlorine Exposure This is the number of years before the build up of chorides on the concrete surface reaches the maximum concentration level 15 assumed that once the maximum is reached it stays at this level forever Time to build to max yrs Define Temperature Cycle Since temperature affects the diffusivity of concrete that is its ability to transport chlorides from the surface to the interior of the concrete Life 365 allows the user to specify annual temperature fluctuations to which the concrete is exposed If the Use defaults box is checked these temperatures are retrieved from the enviornmental conditi
127. tion concentration the solution density the concrete porosity and the concrete density For example seawater has a chloride concentration of approximately 2 percent chloride by mass and has a density of approximately 1 01 kg L If the concrete porosity is 15 percent by volume and has a density of 2 30 kg L the theoretical maximum is Cmax 0 02 x 1 01 x 0 15 2 30 x 100 0 13 This theoretical example calculation would apply to a marine structure below the water line but the critical location is the tidal zone where the concrete is exposed to cyclic wetting and drying During the drying cycle salt crystallization occurs in the concrete pores so the chloride concentration is much higher typically around 0 8 percent Therefore appropriate adjustments to the design values should be based on surface chloride content determinations from structures in similar environments Typically Cmax values are less than 1 0 percent by mass of concrete in uncracked structures Surface chloride build up rate k The rate of chloride build up applies to structures in environments such as bridges and parking structures exposed to periodic deicing salt application or to structures exposed to air borne chloride such as beachfront high rise balconies This parameter is influenced by wash off from rainfall or maintenance and by treatments containing hydrophobic compounds such as sealers The default values in Life 365 are based on deicing salt applicatio
128. tion of the concrete and D the constant chloride diffusion coefficient of the concrete ASTM C1556 is very similar to methods described in earlier publications such as AASHTO T260 1994 Weyers 1983 1992 and NT Build 443 Method NORDTEST 1995 In fact Life 365 uses the NT Build Method to estimate the relationship between the water cementitious material ratio w cm and the 28 day diffusion coefficient see pg 81 in this Users Manual Since then many publications describe how to use ASTM C1556 to estimate the diffusion coefficient and or maximum surface concentration Diffusion Coefficient There are at least three general cases where ASTM C1566 is used to estimate the diffusion coefficient 1 For estimating the initial diffusion coefficient of a concrete mixture most commonly the twenty eight day apparent diffusion coefficient D s 2 For estimating the average diffusion coefficient of concrete in an existing structure such as a 15 year old bridge deck 53 3 For estimating how the diffusivity of a particular concrete standard specimens or sampled from a structure changes over time a sample can be measured and curve fitted at say Day 28 Year 1 and Year 5 values of average diffusion coefficient Concrete field samples do not directly meet the sample requirements in ASTM C1556 but can still be used to estimate diffusion and surface concentration by fitting the data to Fick s second law of diffusion The
129. uires these changes to be the same for all of the alternatives i e if the user changes the probability slider to 75 percent then the probability of all concrete mixtures will be changed to 75 percent Given that the concrete mixtures have different probability functions a change to 75 percent for example will create different service lives To summarize the probability slider shown in Figure 3 28 is ultimately most useful if the analyst can show that one alternative is the life cycle cost effective alternative regardless of the service life uncertainty selected This task should be part of a broader analysis of the sensitivity of the life cycle cost to uncertainty in the economic environmental concrete and cost parameters 3 11 Special Applications Epoxy Coated Rebar Top Reinforcing Only One common practice in concrete slab design is to use epoxy coated rebar for the top layer of steel which is directly exposed to chlorides and a less expensive black steel for the bottom layer using this mixed set of steels gives the structure the benefit of longer service life while keeping steel costs down Life 365 does not have a way to calculate the steel costs of this mixed set it accepts either epoxy coated or black steel as the reinforcing but not both You can however modify the costs of the reinforcing in the Individual Costs tab so that these costs are more accurately captured Here is a simple example using the two figures bel
130. units drop down box to select the units of measure of the chloride exposure and concrete materials if you select SI metric or Centimeter metric as your Base unit then your Concentration units options are wt conc and kg cub m if you select US units then your options are wt conc and Ib cub yd Define Economic Parameters Four parameters are used to set the period and interest rates over which life cycle cost is computed Set the Base year to be the current year or other initial year that is relevant to your analysis Set the Analysis period to be the period of time over which life cycle cost should be calculated 75 years is a common period and Life 365 allows the user to select up to 200 years The Inflation rate is the annual rate at which the prices of goods and services will increase over the future the Real discount rate is the annual rate at which future costs are discounted to base year dollars net of the rate of inflation that 1s it is the real discount rate which does not include the effects of changes in the prices of goods and services Federal infrastructure projects use a discount rate published in OMB Circular No A 94 Life 365 comes with the most recent figures of inflation and discount rate as suggested by the OMB Circular and as published in Energy Price Indices and Discount Factors for Life Cycle Cost Analysis 2006 At the time of this publication the suggested long run real discount rate was 2 0 p
131. vice life Define project costs Compute life cycle cost Analyst Analyst Date 07 12 2013 Settings Help for this window Set default values P About Life 365 Life Cycle Costs Tips This window displays the computed life cycle cost of Base case 13 63 per sq ft 0 00 per sq ft 38 93 per sq ft 52 55 per sq ft each alternative Name Construction Cost Barrier Cost Repair Cost Life Cycle Cost Alternative 1 13 63 per sq ft 0 00 per sq ft 38 47 per sq ft 52 10 per sq ft Graphs Life Cycle Cost by Alternative Constant Costs it Dollars per sq ft Default Settings and Parameters Online Help E z Figure 3 17 LCC Report Tab Finally you can copy and paste results from Life 365 to your own Word and PowerPoint based reports one of two ways First you can take screenshots of the current window that are by default put in your clipboard for pasting In Microsoft Windows a screenshot is taken by pressing the Shift and then PrtSc keys on Apple Computers press Shift Apple and 3 simultaneously to take the screenshot To paste what is now in your clipboard to the Word or PowerPoint document press Ctrl v in Windows or Command v on Apple computers The second way to copy information from Life 365 is to hover the mouse over graphs or tables and right click the mouse a pop up menu will appear e g Figure 3 18 with options to copy the
132. w which no corrosion occurs and above which corrosion is initiated is almost certainly not valid However the risk and rate of corrosion undoubtedly increase as the chloride concentration in the pore solution in contact with the steel surface increases The actual relationship between corrosion and chloride content is likely to be influenced by a whole range of parameters including the type composition and quantity of portland cement and other supplementary cementing materials the moisture content and temperature inside the concrete the porosity and pore structure of the concrete the nature composition of the steel surface and the presence of other species in the pore solution e g alkalis At this time there are no clearly defined relationships that can easily be incorporated into a simple service life model Consequently Life 365 does assume a single chloride threshold value C despite the obvious limitations of such an approach In selecting an appropriate value for C reference was made to the work of Glass and Buenfeld 1995 who presented a comprehensive review of the literature on this topic They found that threshold values published in the literature ranged anywhere from 0 17 to 2 5 percent chloride expressed as total chloride by mass of cementitious material Based on their analysis of the available information they concluded that Without further work no improvement can be made to the suggested chloride threshold levels of 0 4 p
133. which represents the combined effects of inflation and the real discount rate d the latter of which represents the time value of money The nominal discount is defined as the product of the annual inflation rate reflecting changes in the prices and annual real discount rate reflecting the time value of money 1 2 0 104 d Eq 16 Mathematically given a cost which occurs at time but is expressed in terms of prices at time 0 and inflation rate i the current cost of that cost when it occurs is computed as current cost c c 1 i Eq 17 and the present value or constant cost of cost c in year 1 is calculated as 1 A present value constant cost c zu n 1 d 18 25 3 Life 365 M Computer Program Users Manual The concrete service life and life cycle costing methodologies described in Chapter 2 are implemented in the Life 365 Computer Program in a way that allows for easy input of the project structure environmental concrete and economic parameters and for rapid sensitivity analysis of the parameters that most influence concrete service life and life cycle cost This chapter describes how to install start and use the Life 365 Computer Program and then describes additional optional features designed for experienced practitioners 3 1 Installing Life 365 Life 365 runs on personal computers that can run Java including those running Microsoft Windows or Apple OS X It

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