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Winter Maintenance Issues Associated With New Generation Open

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1. Table C 2 British Pendulum Tester Test with PG 76 22 Binder Decor Ar Void Before Aner Change Change IA Matador 213 4 40 3 8 Matador 212 48 40 e 7 Freeze Guard 228 51 43 6 16 Table C 3 Permeability Test with Asphalt Rubber Binder Asphalt Rubber Permeability __ Head Dropin 20 Sec Flow cm sec Flow em sec Flow I1 Decor AirVoid Before After Before Atter Change Change 2 Matador 206 127 119 0635 0595 004 6 Freeze Guard 203 ns 123 058 oss 00 6 Freeze Guard 207 111 121 0555 0605 005 o 61 Table C 5 Average Values of Permeability Test with Asphalt Rubber and PG 76 22 Binders Table C 4 British Pendulum Tester Test with Asphalt Rubber Asphalt Rubber Deter reeze Guard F Meltdown 20 203 42 Meltdown 20 a2 a AV Asphalt Rubber Matador Derer as 7 a Change Change Amer Sl ae a 46 42 9 9 42 42 ERAGE VALUES Permeability Average Values __ Head Drop in 20 sec Flow cm sec Flow cm sec Flow Before Atter Change Change After a os 0o60 oa f e Freeze Guara 205 ma 122 057 os oa 6 Meltdown 20 208 111 123 oss os 0 PG 76 22 Permeability Average Values Head Drop in 20 sec Flow cm sec Flow cm sec Flow After_ Before After Change Change Meltdown 20 13 15 0 675 0 6575
2. Table C 6 British Pendulum Tester Test with Asphalt Rubber and PG 76 22 Binders Asphalt Rubber De Icer sid Meltdown 20 De Icer Meltdown 20 Air Void 20 6 20 5 20 8 PG 76 22 Air Void 21 3 21 5 22 4 BPN Average Values After Before o Change 6e A 2 BPN Average Values 42 39 42 o CEH Change PA Before 48 5 47 5 51 5 After 62 Appendix D Ice Detector Plans and User Manual Hardware There are three main components to the ice detector The first is a series of Thermochron and Hygrochron i Buttons which will be located in the field Up to 98 Thermochrons may be installed just below the surface of the pavement plus at least one Thermochron and one Hygrochron nearby to monitor ambient conditions a total of 100 devices All of the i Buttons may be connected using one pair of 12 gage twisted wire cable because each i Button has a unique internal address and can share communication with the others Figure D 1 shows detail of an embedded Thermochron held in place with epoxy the twisted pair wire would lie in a shallow trench cut in the pavement Figure D 2 shows a set of three test and two control buttons plus an ambient Thermochron and Hygrochron from an existing installation in the Wichita Falls District Thermochron Figure D 1 Thermochron embedded in asphalt pavement Figure D 2 Installation of embedded and ambient sensors on a test section 63
3. stripping raveling e Surface friction e Splash and spray e Noise e Smoothness These indices were ranked on a 5 point scale from 5 excellent to 1 poor A copy of this question and the results are located in the Appendix A as Figure A 4 When analyzing the results indices that were ranked excellent or very good were considered to be the highest performance ratings for NGOGFC Indices ranked as fair or poor were considered to be low performance ratings The number of respondents per index ranked as excellent or very good was calculated Figure 2 5 shows the results from this question NGOGFC splash and spray performance received the overall best rating with fourteen respondents reporting it as excellent or very good Thirteen respondents listed NGOGFC surface friction as excellent or very good thus nearly tying with splash and spray and receiving the next highest performance rating Ten respondents rated both noise level and smoothness as excellent or very good Finally NGOGFC durability performance received the lowest ranking with only seven respondents rating it as excellent or very good and eight respondents rating it as fair or poor 10 Durability m Surface Friction fa Splash amp Spray O Noise m Smoothness Criteria Figure 2 5 NGOGFC performance ratings Tire Stud Rutting Seventeen respondents reported on the frequency of occurrence of tire stud rutting with NGOGEFCs
4. t Want r Maintenance Practicas 2 O 2 13 Field WoTKo AAA A A AA A A dt sa 3 1 4 Recommendations for Winter Maintenance Of PFCs cccncnnccocuccnonocononanonononononccncnnnnanonononoos 3 2 Cold Weather Performance of NGOGFCs National Survey ccsccssssscsssssccsssscsssscccsees 5 Qe A seristens a a a a e eee ev soso as Tee oo 5s Ra eo A Aa 5 2 2 Natonal A O onedaeg apes ON 5 2 I NOC Sr chau a A AAA A A a 6 QF AMET ETI ALOT WSC eaa a aaa aa A a a r SS 6 A E E E E a E a 7 2 3 3 Dis dyanta ges iio 8 DS SUMMA a a a N E R O eo 9 2A Performance and COS dai a e i AAA aa obs Be Ss 9 24 1 Typical Service Lite ia ns 9 2 42 Peron ida idad 10 243 Relative Costra id iia cie 13 LAA SUMMIALY ai ada 13 29 Maite anC oia didcs iba belen 13 2 3 1 Winter Maintenances nn ier ei DEC LA cida Adi 14 E O O 15 20 3 Comparison of D lcing Us it r E A Addis 16 2 3 4 Winter Maintenance Cost aiii 16 DIN Rate Ol ACCES a a e o o e E 16 2 0 0 Permeability NIGMS sans 16 2 6 Other ISSUES viana iaa lisis lan 17 A ML a sen ceceaedss cus aceie coca a E E ASA 17 202 MiX T emperat re sain sce tac aae shan a a tetanus added enema otenaaeuate N a aE 17 2 6 3 Polymer Asphalt Binder ivi ainia dans 17 ANA OS Aside Se a tea each cede ek ie 2s ces oe Ra sae Be Loe Par Ge a 17 2 0 5 Tack Coat Material vi cv ecccz Gsosecn A sai cial AA Baiois ates sede dass ca ii BO 18 2 6 6 Specified Target Air Voids ta 18 20 7 Placement oyver CONCISA Sd 18 A a a E E N 1
5. 10 high gt 10 e Thermal cracking none low lt 5 medium 5 10 high gt 10 SECTION 3 COST What is the relative cost of the material in place compared to the cost of the equivalent depth of a typical ACP surface mix lt typical mix same as the typical mix 15 15 20 20 25 25 30 gt 30 SECTION 4 MAINTENANCE What are the biggest maintenance challenges Rank order 1 8 with being the highest e Pushing shoving and tearing Delamination Stripping difficulties Fuel or oil spills Snowplow damage Stays frozen longer Formation of black ice Other Are special activities used to maintain the surface condition of NGOGFC pavements e No special activities e Fog seal e Others Are special major maintenance activities used on NGOGFC pavements e No special activities e Cleaning to restore permeability e Others What are the current winter maintenance techniques used in your region How effective are they Ineffective 1 Moderately effective 2 Effective 3 Very effective 4 e Sanding 48 Magnesium Chloride and CF 7 Prewetted salts Advisory signs None e Liquid de icer agent e Anti icing agent e Magnesium Chloride e CMA e Larger quantity de icer e Run shoes on plows e Reduce plow speeds e Rubber bits e CMA amp CF7 Oo e Oo e For NGOGEFCs percentage wise how much additional de icing chemical is needed e None e 25 e 50 e
6. Eleven 65 respondents reported no occurrence three 18 respondents cited low occurrence two 12 cited high occurrence and one 6 cited medium level occurrence Icing Frequency Fifteen respondents reported on the frequency of icing with NGOGFCs Five respondents 33 reported over 10 days of icing with NGOGFCs per year Three 20 experienced 5 to 10 days of icing per year and another three 20 experienced less than 5 days of icing Twenty seven percent stated that they never experienced icing with NGOGFCs Raveling in Wheel Paths A total of seventeen respondents reported on the percentage area of raveling in wheel paths with NGOGFCs Ten 59 respondents reported less than 5 area of raveling Five 29 reported over 25 area of raveling and two 12 respondents reported 5 to 25 area of raveling with NGOGFCs Gouging or Scarring Fifteen respondents reported on the percentage level of gouging or scarring from snowplows and other machinery with NGOGFCs Eight 53 reported less than 5 area of gouging or scarring Four 27 reported an area of 5 to 25 and three 20 reported an area of greater than 25 Deformation Rutting A total of sixteen respondents reported on the average depth of deformation rutting with NGOGECs The average depth of deformation rutting was calculated on a scale from none to high An average depth of 0 25 in or less was considered to have an average depth of none 0 25 0 5 in
7. depths The onset depth and duration of black ice formation were recorded for each specimen Permeability of the specimens prepared for this study was measured and their relation to the duration of black ice formation was evaluated Additionally friction properties of the specimens before and after black ice formation were evaluated The surface reflectivity of the specimens was determined at this time according to the procedure that is set in this experiment In addition the effect of the most important factors on winter performance was evaluated in terms of effect on permeability and friction The most common winter maintenance techniques used include the application of salt sand and de icing chemicals to the pavement with black ice The first factor to be evaluated is the effectiveness of the various types of winter maintenance techniques on permeability and friction The second factor was what effect repeated applications of winter maintenance techniques had on the permeability and friction of PFCs 3 2 Equipment e British Pendulum Tester e Permeameter e Thermochrons e Hygrochrons 21 3 2 1 The British Pendulum Tester The British Pendulum Tester 8 is one of the simplest and cheapest instruments used in the measurement of friction characteristics of pavement surface It is extremely versatile in its applications to many test situations and has received acceptance worldwide The test device measures low speed friction about 10 km
8. other issues relating to NGOGFC material properties and a final section for respondents comments The survey included a total of 57 questions and was distributed as both PDF and Excel files 2 3 NGOGFC Use Out of 26 respondents to the survey 11 42 use NGOGFCs 5 19 never used NGOGEFCs and 10 38 have discontinued its use Of those who have used but no longer use NGOGFCs 64 cite performance as the reason for discontinuation 45 cite maintenance problems and 36 cite other reasons Zero percent report cost as the reason for discontinuing use of NGOGFCs Six 26 respondents reported that they use NGOGFCs on roads with speed limits less than or equal to 45 mph Fourteen 61 respondents use NGOGFCs on roads with speed limits over 45 mph Seven 32 respondents reported that they have used NGOGFCs in curb and gutter sections and 15 68 reported that they have not 2 3 1 Criteria for Use The questionnaire listed eight issues that agencies may use to determine whether or not to use NGOGFC mixes in their area with the option of listing other criteria used in their decision making process These eight criteria included the following e Traffic level e Environment freezing or not wet or dry e Skid resistance e Noise e Reduced splash and spray e Smoothness e Cost e Durability Respondents were asked to rank the criteria from 1 to 9 with 1 being the most important criteria A copy of the question and results is
9. three to five per mile of fat spots or bleeding and one 6 respondent reported a high level more than five per mile Noise Level inside Vehicle Out of fifteen respondents twelve 80 reported low noise level inside the vehicle with roads paved with NGOGFCs Two 13 respondents reported a medium noise level and one 7 respondent reported a high noise level Stripping Seventeen respondents reported on the percentage area of stripping with roads paved with NGOGEFCs Nine 53 reported a smaller than 5 area of stripping Two 12 reported a 5 to 25 area and one 6 respondent reported an area of stripping of more than 25 with NGOGFCs Five 29 respondents stated that they did not know the percentage of stripping with NGOGFCs for their respective areas New Construction Roughness IRI Thirteen respondents reported on the new construction roughness IRI with NGOGFCs Four 31 reported a very smooth surface less than 40 IRI Six 46 reported a smooth surface 40 60 IRI and three 23 respondents reported an average surface smoothness 60 80 IRI Zero respondents reported a rough surface over 80 IRI 12 Reflective Cracking Out of fifteen respondents seven 47 reported that NGOGFCs in their areas experienced reflective cracking Eight 53 respondents reported no reflective cracking with NGOGECs in their respective areas Thermal Cracking Out of fifteen respondents four 27 reported that the
10. The second component of the ice detector is the control box which will be mounted on an existing or purpose installed pole near the roadway The control box will contain an HA6 transceiver connected to the i Button network and a sealed lead acid storage battery to power the HA6 A photovoltaic panel will be mounted above the control box to charge the battery during daylight hours The HA6 is a low power device consuming 200 ma when actively transmitting but only 20ma when quiescent which is most of the time since the HA6 will be placed in query mode This allows the device to operate at full power only when instructed by the remote operator to transmit data or receive commands Figure D 3 shows the HA6 The HA6 has an RJ 11 telephone jack on the front panel to connect to the i Button network Figure D 3 TZR and HA6 transceivers Figure D 4 shows the completed assembly minus high gain antenna and details of the solar panel attachment The solar panel and holder clamp to the post using two U bolts as shown The solar panel must be pointed to the south and angled for optimal sun exposure A table is available from the manufacturer showing the optimal sun angle and also the necessary battery amp hour capacity which depends on the installation location the current draw of the radio and the duty cycle Figure D 5 shows a contour map used in this process As can be seen most of western Texas is in a high solar radiation zone that
11. Various Field Conditions Research Report 1700 1 Center for Transportation Research The University of Texas at Austin 2003 43 12 Dossey T C Medina and B F McCullough Analysis and Validation of the Usefulness of the Rigid Pavement Database Final Report 1778 6 Center for Transportation Research The University of Texas at Austin 2004 Appendix A National Survey Questionnaire SECTION 1 NGOGFC USE Do you currently use PFCs or NGOGFCs e Yes e Never have used it e Used before but not now If you ve used it before but not now please indicate the reason e Maintenance Problems e Cost e Performance e Other Where do you use NGOGFCs e Urban gt 45 mph lt 45 mph Other e Rural gt 45 mph lt 45 mph Other Have you used NGOGFC in Curb and Gutter Sections e Urban Yes No e Rural Yes No What criteria are used to select an NGOGFC mixture Check all that apply Rank in order of 1 9 with being the highest Traffic level Environment freezing or not wet or dry Skid resistance Noise Reduced splash and spray Smoothness Cost Durability Other 45 What are the advantages of using NGOGFCs in your region Rank order of 1 7 with 1 being the highest Improved driver visibility on wet pavement reduced spray Improved wet weather skid resistance Improved road marking visibility during wet weather Noise Cost Durability Other What are the disadvantages of using NGOGFC
12. anti icing agent and pre wetted salt When considering black ice respondents reported anti icing agents to be the most effective Sanding followed with an average rating of 3 40 prewetted salts 3 13 and liquid de icing agents 2 86 Advisory signs ranked lowest as an effective technique for mitigating black ice averaging 1 75 A full 54 of respondents stated that NGOGFC mixes increase their maintenance costs by 25 or more According to respondents NGOGFC mixes are rarely measured or monitored This is clearly demonstrated by 81 of respondents claiming to never measure permeability of NGOGFC mixes in their region while the remainder 19 claim that they do not know if their state monitors this factor Twenty one percent of respondents specify air voids less than 15 contrary to the definition of NGOGFC Twenty one percent of respondents add rubber as an additive to NGOGEC and three fourths of this 21 of the respondents say this additive is better than other additives Additionally the most common additives were cellulose 38 and use rubber 25 When considering the composition of NGOGFC mixes 88 of respondents use polymer asphalt binders 5 2 Lab Results for Permeability and Abrasion Testing When considering cold weather maintenance of NGOGFC mixes black ice formation is a high level concern A laboratory study used PFCs mixes under laboratory conditions to examine the conditions under which black ice forms in this case a measuremen
13. events as compared to de icing procedures Anti icing procedures involve a combination of liquid dry solid and pre wetted chemicals applied at the appropriate times taking into consideration temperature the amount of moisture and traffic conditions De icing procedures should be reserved for events in which ice and snow have already bonded These procedures generally require more materials and do not maintain safe road conditions as well as anti icing procedures Sand should be used only in emergency situations where quick friction is needed such as during a surprise ice or snow event Use of sand on PFC pavements may cause clogging which reduces their draining benefits Other materials may be used to generate the needed friction 41 LEGEND co Line zone 1 100 moh wing Zone 2 0 90 mon wine Zone 3 BBB 20 mon wina zone 4 7 70 mon wine Figure 5 1 Texas Ice and Wind Map 42 References 1 Kandhal P V Design Construction and Maintenance of Open Graded Asphalt Friction Courses Information Series 115 National Asphalt Pavement Association Lanham Maryland 2002 2 Geistlinger L Safety First Open Graded Friction Courses Roads and Bridges September 1996 3 Mallick R B P S Kandhal L A Cooley Jr and D E Watson Design Construction and Performance of New Generation Open Graded Friction Courses National Center for Asphalt Technology Auburn University 2000 4 Smith H A Performa
14. events were accompanied by some form of precipitation One such freezing events which took place on November 29 2004 is illustrated in Figure 4 4 with a plot showing the temperatures recorded by the three sensors embedded in the NGOGFC pavement pfcl pfc2 and pfc3 the temperatures from the sensors in the control section and the ambient sensor temperatures The onset and duration of the snowfall event superimposed on the chart was obtained from NCDC precipitation records 31 35 40 45 5 0 Elapsed Time days Figure 4 4 Snowfall event at Amarillo test section November 29 2004 The focus of the chart is narrowed even further in Figure 4 5 to show the individual data points from all the sensors during this first freeze event As expected the three NGOGFC sections show a brief temperature plateau at exactly 32 F latent heat being released as the water freezes whereas the two control sections do not This confirms that the NGOGFC surfaces are more susceptible to the development of black ice than the conventional dense graded pavements 32 Possible Icing on PFC Ambient Sections pfol YO pfe2 hae a pfc3 Ctrl1 ctri2 Y Control Sections 3 8 3 9 4 0 4 1 Elapsed Time days Figure 4 5 Possible evidence of black ice in NGOGFC section in Amarillo November 29 2004 The remaining freeze events with precipitation and those
15. h and is commonly used to assess the microtexture of pavement surface The values measured BPN British Pendulum Tester Number for flat surfaces and polish values for accelerated polishing wheel specimens represent the frictional properties obtained with the apparatus and the procedures stated herein and do not necessarily agree or correlate with other slipperiness measuring equipment Figure 3 1 shows a British Pendulum Tester ene o o Figure 3 1 British Pendulum Tester 3 2 2 Permeameter The Permeameter measures the permeability of porous asphalt road mixes under laboratory conditions This apparatus works on the falling head principle from which the falling head with time through a porous specimen is measured with a precise pressure transducer at very close time intervals 10 readings s Using the falling head data the specific discharge through the specimen can be computed and the permeability of the material obtained from the velocity versus hydraulic gradient relationship 9 Figure 3 2 depicts an image of the Permeameter 22 Figure 3 2 Permeameter 3 2 3 Thermochrons Thermochrons or i Buttons are the size of a thick dime and contain a temperature sensor a battery a network interface and computer memory With a waterproof coating of epoxy or latex they can be reliably embedded in asphalt or concrete pavement and log precise temperature data effectively for a period of up to 10 years taking a reading ev
16. it may still accumulate moisture through rain snow or sleet and during freezing events black ice can be produced 5 1 National Survey of Practice The objective of the survey was to establish regional patterns of NGOGFC use and issues related to performance cost maintenance and material properties For the purpose of the survey only NGOGFC mixes were considered NGOGFC mixes are distinguished from their predecessor by having at least 18 air voids and in many cases containing polymer modifiers and or asphalt rubber Surveys were distributed to TxDOT districts and state DOTs 26 state DOTs responded including Arizona Alaska California Connecticut Florida Georgia Indiana Kansas Kentucky Nebraska Nevada New Hampshire New Jersey New Mexico New York North Carolina Maine Ohio Pennsylvania Montana South Carolina South Dakota Tennessee Texas Vermont and Washington Additionally within California three cities responded namely Eureka Oakland and Sacramento Results of this survey determined that 82 of survey participants either use or have used NGOGFC mixes in their region In all 38 of total survey participants have discontinued use of these mixes for various reasons including performance and maintenance problems these states include the following Connecticut Ohio Indiana Pennsylvania Montana New York South Carolina Vermont and Washington Additionally the three cities within California which are Eur
17. real time control and monitoring of the devices The same equipment will also allow maintenance personnel to monitor the effective depth and duration of anti icing or de icing chemicals applied to the pavement during actual icing conditions The complete plans for the ice detection and monitoring system are given in Appendix D of this document The custom software for device communication and monitoring has been provided on CD ROM along with all drawings schematics parts list estimated costs instructions for installing and using software and supplier information for each component All parts of the system are readily available off the shelf At the time of this writing an implementation project to test the complete system including real time monitoring is in the contract phase and is expected to begin in late February or early March 2007 5 4 PFCs Construction and Maintenance Related to Geographic Location In Texas severe winter weather events are confined to the northern section of the state as shown in Figure 5 1 North of the ice line is where ice and snow are most likely to occur If PFC pavements are constructed the northern part of Texas delimited by the ice line district personnel must be ready to implement winter maintenance strategies for such pavements As indicated in the literature and the current practice of TxDOT districts anti icing procedures may produce the best result to combat black ice freezing rain and light snow
18. taken together with the very low amp draw of the HAG transceiver requires only a fairly small battery in the control box The Thermochrons and Hygrochrons have internal batteries and will continue to operate and store data even if the control box battery is completely discharged Should that happen the HA6 will resume functioning and can transmit all stored data when the battery is recharged requiring no operator intervention The HA6 will operate on any voltage between 6 VDC and 24 VDC 64 Figure D 5 Solar radiation zones in the United States Although any sturdy case for the control box can be machined to fit purpose built boxes for remote solar powered instrumentation exist and are ideal for this assembly because they are galvanized fiberglass and aluminum are also available vented have a locking hasp and pre installed pole mounts and internal battery mounts and even include a weather tight connector for RF antenna connection Figure D 6 shows the layout of one such commercially available enclosure 65 HASP ATTACHED 70 NOOR W SOE VEW OF er Ai A BBA 1M ALUMINUM ENCLOSURE SCALE 2 5 maso atrarcuen ro sopr ML NOTES 1 CABINET DIMENSIONS INSIDE 16 X 16 W x 10 D 2 STAINLESS STEEL PAD LOCKASLE HASP 3 STAINLESS STEEL HINGE 4 SCREENED LOUVERS ON DOOR FOR VENTILATION 5 13 000 X 14 125 BACK PANEL NOTES 4 3 2 1 Figure D 6 Diagram of a p
19. the experimental sections has been retrieved regularly from each site after the winter seasons but in the next phase of this study wireless capabilities for remote real time monitoring will be implemented as presented in the last section of this paper 4 4 Experimental Results The installation of the field devices was successful and their performance has been very satisfactory as shown by the data downloaded in the various collection trips Very few sensors have failed These cases are attributed to internal battery failure and not to damage by traffic loads Those sensors that have failed have been replaced by new ones The development of black ice in the pavement requires both freezing temperatures and the presence of water from rain or melted ice and snow North Texas had fairly dry winter seasons throughout the duration of this project The National Climatic Data Center NDC http www noaa gov climate html records revealed not one day in either the Wichita Falls or the Fort Worth District sections in which both freezing temperatures and precipitation were recorded but many occurrences in Amarillo This observation coincides with the data from the field and the recollection of district maintenance personnel who were contacted shortly after the data was analyzed The Amarillo section for instance experienced more than fifteen freezing events between November 25 2004 and March 4 2005 The NCDC database indicates that five of these freeze
20. was considered to be of low average depth 0 5 0 75 in was considered as medium 11 average and greater than 0 75 in was considered high Twelve 75 the clear majority reported an average depth of none Three 19 respondents reported a low average depth one 6 reported a medium average depth and zero reported a high average depth of deformation rutting Clogging Seventeen respondents reported on the incidence of clogging with NGOGFCs based on splash and spray Only one 6 respondent reported zero clogging with NGOGFCs Six 35 respondents reported low levels of clogging Another six 35 reported medium levels and two 12 respondents reported high levels of clogging with NGOGFCs Two 12 respondents stated that they did not know the level of clogging in their areas Potholes A total of sixteen respondents reported on the number of potholes occurring with NGOGEFCs in their respective areas Five 31 reported no potholes ten 63 respondents reported a low level of potholes fewer than three potholes per mile No respondents reported a medium level of potholes three to five per mile and one 6 respondent reported a high level of potholes more than five per mile Fat Spots or Bleeding Sixteen respondents reported on the incidence of fat spots or bleeding with NGOGFCs Three 19 reported no fat spots or bleeding Twelve reported low levels fewer than three per mile Zero respondents reported a medium level
21. were once again asked to rank the advantages from 1 to 6 with 1 being the biggest disadvantage When analyzing the results criteria that were given the rankings through 3 were considered to be the biggest disadvantages to using NGOGFC The number of respondents per category ranked 1 through 3 was calculated Figure 2 3 shows the results from this question Winter maintenance problems were considered to be the biggest disadvantage with 9 respondents ranking this category in the top three Initial or construction cost followed with 8 respondents ranking it in the top three Durability performance and general maintenance were tied with 6 respondents each No additional disadvantages were identified 10 o 9 8 El O Initial Cost 8 6 m Winter Maintenance 9 5 G Durability pe 4 O Performance g m 10 12 Years 2 2 51 0 Criteria Figure 2 3 Disadvantages of using NGOGFC pavements 2 3 4 Summary Eighty two percent of the 26 respondents stated that they had used NGOGFCs at some point Approximately half of the 38 who had discontinued use cited performance and maintenance issues as the primary reason Cost was not a significant factor in respondents decisions to discontinue use of NGOGFCs Overall respondents cited high wet weather skid and spray performance as the main advantage with using NGOGFCs whereas winter maintenance initial cost and durability were reported as the greatest dis
22. 0 250 F Is polymer modified asphalt binder used in NGOGFC e Yes e No What other additives are used e Rubber e Cellulose fibers e Rock fibers e Other If rubber is used how does the performance compare to NGOGFCs without rubber e Better e No change e Worse If rubber does affect performance on which indices does it have the most impact e Structural Durability i e stripping raveling etc e Surface Friction e Splash and Spray e Noise e Smoothness If fibers are used how does the performance compare to NGOGFCs without fibers e Better e Nochange e Worse If fibers do affect performance on which indices do they have the most impact e Structural Durability i e stripping raveling etc e Surface Friction e Splash and Spray e Noise e Smoothness What type of tack coat material is used e Emulsion e Hard asphalt e None e Other 51 What is the specified application rate of tack coat in gal sq yd e lt 0 05 e 0 05 0 07 e gt 0 07 e Other e N A What are the specified target air void requirements for NGOGFC lt 12 12 15 15 18 18 20 Other Have you placed NGOGFC over newly constructed concrete pavement e Yes e No Have you placed NGOGFC over existing concrete pavement e Yes e No If you placed NGOGFC over existing concrete pavement what pre treatment was used e None Milling Grinding Seal Coat Tack Coat Rubberized 52 1 Traffic Level 2 Envir
23. 75 e 100 How much more do you spend on salt de icers etc for NGOGFC pavements e Same e 25 e 25 50 e 50 75 e 75 100 What maintenance techniques have worked best for your area Anti icing Sanding Use of salts Use of liquids Use of prewetted salts Advance warnings signs Other None Have you observed an increase in the rate of accidents on NGOGFC pavements during non freeze events e Yes e No e Don t know 49 What kinds of maintenance techniques do you use to counter black ice How effective are they Ineffective 1 Moderately effective 2 Effective 3 Very effective 4 e Sanding Liquid de icer agent Anti icing agent Magnesium Chloride CMA Larger quantity de icer Run shoes on plows Reduce plow speeds Rubber bits CMA amp CF7 Magnesium Chloride and CF 7 Prewetted salt Advisory signs None Is permeability of NGOGFC pavements monitored periodically e Yes e No e Don t know How often is permeability measured e When constructed e Every __ months e Annually e Other How is permeability measured e NCAT procedure e Other SECTION 5 OTHER ISSUES Is the range of asphalt content specified e Yes e No If the range of asphalt content is specified what is the percentage rate e N A e 5 6 e 7 8 e 9 10 e 11 12 50 What mix temperature range has been established to prevent asphalt draindown e 190 200 F e 200 215 F e 215 230 F e 23
24. 9 2 7 Comments from Selected States h a a a A a A E ain 19 DAM California eraen iia di 19 A b tas ica N WE brads Unie tlle docs ies tac hans lait es Stas Lased babes 19 DTS UNEP SCALES ho a a E E asses ee oT awe Aas TRESS 20 3 Cold Weather Performance of PFCs Lab Report sccssssccssssscssscccsscccssscsssssssessescesees 21 Se UUMUOGUCIIOM sans aisre O 21 3 2 AGUA IIS iaa 21 3 21 The British Pendulum Tester a ito 22 vii 3 22 PerME AME ter EEEE EE E atada 22 A Se LMCI GC OMS oc ec snd aig uace te yea asad acta sued ech eats iat E e toads EEEE OEE sence Rain 23 3 2 4 Hy LOCO A 24 A E A a a a AS E O S 24 DAE Tasks O 24 341 Permeabilidad E E A R A A A 24 3 4 2 Fiction Properties Na EES 23 XS Res lts andanada 25 3 5 1 Permeability sreci a a R E S EA E ARA iit 25 392 Friction Properties 26 Ae IMS HU Te DETECTO sssini eessen seseo aaee essensa 27 4t Field A a A a e E E TRS 27 4 2 Concept of Latent Heat Of Fusion aa RE E 29 4 3 Selection and Instrumentation of Field Test Sections ooooonocccnnoccconacaconancnonnnncnnnccnonnccnnnnnon 30 4 4 Experimental Result ii aa 31 As o A A a E 33 4 6 Conclusions and Future implementation 5 5 3ssssccseaisecessseseqedseiaqeanciaacc ovatvecedeaisosancaenereeusienve 35 5 Conclusions and Recommendations eesesseseessesessossesossossesossossessossesossossesossossessosoesossossesossse 39 IL National Survey Ol ao tds 39 5 2 Lab Results for Permeability and Abrasion Testing oooo
25. Increase in Energy _ Zp 212 F 32 F ICE MELTING LIQUID BOILING STEAM Figure 4 3 Phase change temperature plateaus illustrating latent heat of fusion in water 4 3 Selection and Instrumentation of Field Test Sections After selection and validation of the instrumentation the next step taken was to choose field test sections There were only two criteria for section selection the first being high probability of freezing weather and precipitation and the second requiring the existence of NGOGEC sections It was also highly desirable to have conventional nonporous asphalt sections nearby for use as control sections to help distinguish between frozen precipitation falling on the section versus freezing of water within the pavement The region of Texas north and west of Dallas Fort Worth routinely experiences freezing precipitation and the only existing NGOGFC pavements in this climate area are located in the Amarillo Wichita Falls and Fort Worth Districts Accordingly three test locations were selected for the experiment in those TxDOT districts Each of these locations had the following instrumentation installed e Three Thermochrons embedded in the NGOGFC section e Two Thermochrons embedded in an adjacent dense graded conventional asphalt section control section for comparison purposes e One or more Thermochrons and one Hygrochron adhered with epoxy to a traffic sign or other permanent object next to the section to mo
26. Technical Report Documentation Page 1 Report No 2 Government Accession No 3 Recipient s Catalog No FHWA TX 08 0 4834 2 February 2007 Winter Maintenance Issues Associated with New Generation Open Graded Friction Courses Author s 8 Performing Organization Report No Yetkin Yildirim Terry Dossey Ken Fults Maghsoud 0 4834 2 Tahmoressi and Manuel Trevino 9 Performing Organization Name and Address Center for Transportation Research 11 Contract or Grant No The University of Texas at Austin 0 4834 3208 Red River Suite 200 Austin TX 78705 2650 12 Sponsoring Agency Name and Address 13 Type of Report and Period Covered Texas Department of Transportation Technical Report Research and Technology Implementation Office Sept 2004 Aug 2005 P O Box 5080 14 Sponsoring Agency Code Austin TX 78763 5080 15 Supplementary Notes Project conducted in cooperation with the Texas Department of Transportation and Federal Highway Administration Project Title Cold Weather Performance of New Generation Open Graded Friction Courses 16 Abstract The improved ride quality and other possible safety benefits associated with New Generation Open Graded Friction Course NGOGFC or Permeable Friction Course PFC pavements better friction lower noise less splash and spray higher visibility reduced hydroplaning and reduced nighttime surface glare in wet weather conditions have made them highly attractive to engineers and contractors in the l
27. advantages of NGOGFC use The respondent states that use NGOGFCs are Arizona California Florida Georgia Kansas Nebraska Nevada New Jersey North Carolina Tennessee and Texas The respondent states that have discontinued use are Connecticut Ohio Indiana Pennsylvania Montana New York South Carolina Vermont and Washington respondent cities that have discontinued use are Eureka Oakland and Sacramento California The respondent states that do not use NGOGEFCs are Alaska Kentucky New Hampshire New Mexico Maine and South Dakota 2 4 Performance and Cost 2 4 1 Typical Service Life Nineteen respondents reported on the estimated average typical service life of NGOGFC in their respective areas Five 26 reported that NGOGFCs lasted less than 6 years Another five 26 reported that NGOGFC lasted between 6 and 8 years Four 21 reported that NGOGECs lasted between 8 and 10 years Three respondents 16 said it lasted 10 to12 years and only two 11 said it lasted more than 12 years Figure 2 4 summarizes the responses to the service life of NGOGFCs 6 0 E5 o 4 a O lt 6 Years 4 cece m6 8 Years 83 E m8 10 Years E E 110 12 Years o2 E m gt 12 Years oO o 2 bs E 1 a 5 o Number of Service Years Figure 2 4 Service life of NGOGFC pavements 2 4 2 Performance Performance Rating Performance was rated in terms of five indices including e Durability e g
28. agencies to establish the patterns of NGOGFC use and issues related to performance and cost maintenance and material properties Results of this survey will be used in coordination with results from a study of NGOGFC in the field The discussion that follows will review the results of the survey 2 2 National Survey An online survey of the use mix design construction and general and winter performance and maintenance was distributed to TxDOT districts state DOTs and international agencies The objective of the survey was to gather information on NGOGFC design maintenance performance issues and current practice by region Information related to the cold weather performance of NGOGFCs and associated practices was also collected Twenty six responded to the survey These responses were compiled and analyzed to obtain specific information about NGOGFC mixes The results are presented according to specific questions asked in the survey The survey was specifically for NGOGFCs only stating that NGOGFCs have at least 18 air voids and many contain polymer modifiers and or asphalt rubber The survey was not intended to address old plant mix seals or old generation OGFCs The survey did note however that in Texas NGOGFC pavements are often referred to as PFC permeable friction course pavements therefore these pavements were also included in the survey The survey was organized according to NGOGFC use performance and cost maintenance
29. ast 3 decades Nevertheless the durability problems and performance and maintenance issues exhibited by NGOGFCs under winter weather conditions especially the fast formation of black ice have prevented their widespread use Recent research has investigated new preventive methods and materials for handling these winter maintenance issues and improving durability in NGOGFCs In 2005 the Center for Transportation Research CTR conducted an online survey of different districts within the Texas Department of Transportation TxDOT to gather information on NGOGFCs and in 2004 2005 CTR conducted lab and field experiments to test the methodology for detecting black ice formation on NGOGFCs This report presents the findings of the CTR survey results and research 17 Key Words 18 Distribution Statement Open Graded Friction Course permeable mixes No restrictions This document is available to the noise skid black ice winter maintenance wet public through the National Technical Information weather accidents Service Springfield Virginia 22161 www ntis gov 19 Security Classif of report 20 Security Classif of this page 21 No of pages 22 Price Unclassified Unclassified 82 Form DOT F 1700 7 8 72 Reproduction of completed page authorized N Winter Maintenance Issues Associated with New Generation Open Graded Friction Courses Yetkin Yildirim Terry Dossey Kenneth W Fults Maghsoud Tahmoressi Manuel Trevino CTR Techn
30. case the devices were retrofitted into the pavements by drilling and sealing with quick set epoxy The purpose of this experiment was to determine the minimum internal temperatures of the concrete during the winter season Data from the 3 years of the field study also indicated that the presence of ice on the pavements could easily be detected Fig 4 2 28 December 02 Top Figure 4 2 Ice on CRCP Amarillo Texas 4 2 Concept of Latent Heat of Fusion The specific latent heat of fusion of a substance is the amount of heat required to convert a unit mass of the solid into the liquid or vice versa without a change in temperature The 335kJ specific latent heat of fusion of ice at 0 C is s This means that to convert 1 kg of ice at 0 C to 1 kg of water at 0 C 334 kJ of heat must be absorbed by the ice Conversely when 1 kg of water at O C freezes to give kg of ice at 0 C 334 kJ of heat will be released to the surrounding area During freezing this energy is released while the measured temperature of a porous pavement remains constant at 0 C until all the water has changed phase from liquid to solid and vice versa for thawing This characteristic temperature plateau Fig 4 3 can be readily detected by the embedded sensors and is positive proof that ice is present if the plateau does not appear in an analogous ambient measurement taken away from the pavement 29
31. ced problems with lack of durability and winter performance and maintenance issues such as raveling within a short period of time clogging of the open permeable pores and fast ice and frost accumulations all of which led to a discontinuation of the mixes However changes in open graded mixture technology in the past decade have brought increased interest in the use of new generation open graded friction courses NGOGFCs or Permeable Friction Courses PFCs Currently many countries in Europe including Austria Belgium France Germany Italy the Netherlands Spain Switzerland and the U K as well as several states in the U S mostly in the western and southern regions including Arizona Georgia Oregon Texas and Utah are using PFCs 2 PFCs are more open graded have increased air void structures at a minimum of 18 contain more asphalt 20 or more and are enhanced with polymer asphalt rubber asphalt and fiber additives 3 Potential benefits of PFC mixes are lower noise improved visibility in wet weather conditions reduced splash and spray reduced hydroplaning reduced night time surface glare and improved skid resistance The permeability of PFCs allows water to be removed from the surface of the road at a faster rate than that occurring in conventional pavements High speed traffic helps to clean the voids in the PFC by the pumping action produced by the vehicular tires PFCs that are polymer modified and contain fibers with l
32. ck of durability and winter performance and maintenance which caused some areas to discontinue use of the mixes Because of changes in open graded mixture technology in the past decade there has been increased interest in the use of NGOGFCs or permeable friction courses PFCs as they are known in Texas NGOGFC mixes are more open graded have increased air void structures have more asphalt and are enhanced with polymer asphalt rubber asphalt and fiber additives The design of the NGOGFC has reduced some of the durability problems associated with the first generation mixes 7 However it is unclear whether or not advances in NGOGFC technology will solve the problems with performance in winter conditions These open mixes may still allow accumulations of moisture through rain snow or sleet and during rapid freezing events black ice can be produced which can be a serious concern for vehicles traveling at high speeds or with improper tire inflation or tread depth Many regions prone to snow or ice have not considered using NGOGFCs because of their potential winter problems but some countries in Europe have established winter maintenance programs to address these potential safety concerns These programs have also been implemented by some states in the U S In order to answer specific questions surrounding the actual use of NGOGFC mixes a survey was distributed to TxDOT districts state departments of transportation DOTs and international
33. d by solar energy with a small lead acid battery for energy storage Fig 4 10 The researchers have tested the system s range successfully at a distance of 11 miles theoretically a 22 mile range can be achieved with a Yagi directional antenna Fig 4 11 operating line of sight Therefore the sensors can be located within that distance from a district maintenance office from which the formation of black ice can be monitored and proper action taken should such events occur The transceivers are frequency hopping meaning that they use a method of transmitting radio signals by rapidly switching frequencies using a sequence known by both transmitter and receiver as opposed to a fixed frequency transmission This makes the signal very resistant to noise and interference which is especially useful in an urban environment The field sensors can be both read and programmed from the remote location e g maintenance office through the point transceiver The network wireless devices will be installed at various sites to e Implement real time pavement temperature monitoring to better dispatch maintenance crews when icing is imminent e Detect ice not only in NGOGFC sections but also in bridges Ice formation in bridges is a dangerous occurrence for drivers and causes many accidents thus TxDOT will expand the implementation of this technology to this type of structures e Monitor the effectiveness of de icing measures in real time e Verify the
34. eability data from these specimens are included in Table 3 1 Then the specimens were saturated and frozen Later three different maintenance methods were applied to the specimens Afterwards the permeability of the specimens was measured again This data is also presented in Table 3 1 Table 3 1 Permeability Test Comparison Test Results Asphalt Rubber and PG 76 22 Binders Permeability Asphalt PG 76 22 Asphalt PG 76 22 Asphalt PG 76 22 Rubber Rubber Rubber Matador 0 635 o7 0595 os5875 6 e As can be seen from the data all the specimens prepared with PG 76 22 binder showed a decrease in permeability Specimens treated with Matador a liquid anti icing agent and Freeze Guard another liquid anti icing agent showed 15 and 16 decreases in permeability respectively The specimens treated with Meltdown 20 a solid de icing agent showed only a 3 decrease in permeability Specimens prepared with asphalt rubber binder showed varying results The permeability of the specimens treated with Matador decreased by 6 On the other hand specimens treated with Freeze Guard a liquid anti icing agent and Meltdown 20 a solid de icing agent resulted in a 7 and 11 increase in permeability respectively 25 3 5 2 Friction Properties The friction properties of the specimens before and after black ice formation and the application of winter maintenance treatments are included in Table 3 2 In all cases application of winte
35. effectiveness of existing ice control devices installed in some bridges 36 Figure 4 9 Transceivers for the wireless network Figure 4 11 Yagi directional antenna with 22 mile range line of sight 37 5 Conclusions and Recommendations This report presents findings from three important sources 1 a nationwide survey of practice for NGOGFC pavements 2 laboratory results for permeability and abrasion testing on PFC specimens and 3 development of a methodology for remote detection of ice formation and for remote monitoring of the effectiveness of deicing compounds in field pavements Conclusions and recommendations in each area are given below Also a recommendation regarding PFC construction and maintenance as it relates to geographic location in the state of Texas is presented in the final section of this chapter New Generation Open Graded Friction Course NGOGFC mixes have many safety and noise benefits including good friction lower noise reduced hydroplaning high visibility reduced splash and spray and reduced nighttime surface glare in wet weather conditions New Generation mixes are more open graded than their predecessor early Open Graded Friction Course and the design has reduced some durability problems associated with early Open Grade Friction Course mixes These improvements however may or may not address early Open Graded Friction Course mix s problems with winter performance and maintenance because
36. eka Oakland and Sacramento have also discontinued use of NGOGFC mixes Cost was not a significant factor in respondents decisions to discontinue use of NGOGFCs When considering criteria for NGOGFC use survey participants indicated that skid resistance followed by noise and reduced splash and spray are the most important factors for consideration Advantages of NGOGFC were determined to be improved driver visibility on wet pavement improved wet weather skid resistance and improved road marking visibility during wet weather The greatest disadvantages seen by survey participants were winter weather maintenance and initial cost of construction followed by durability performance and general 39 maintenance These survey results will be combined with results of a field study on NGOGFC mixes NGOGFC maintenance challenges presented in the survey include the following pushing shoving and tearing slippage cracks stripping difficulties fuel or oil spills snow plow damage stays frozen longer and the formation of black ice According to survey participants the occurrence of black ice is the most significant issue related to NGOGFC mixes followed by roadways staying frozen longer and snow plow damage Zero respondents ranked pushing shoving and tearing slippage cracks stripping and fuel or oil spills as the most significant problem with NGOGFCs Mitigating techniques that are used most often in icy conditions include liquid de icing
37. en Thermochrons and one Hygrochron will be needed for each location Table D 1 Itemized Cost to Assemble One Remote Monitoring Station Part Cost Supplier Function HA 6 Transceiver 249 Embeddeddatasystems com Field controller TZR Transceiver 349 Embeddeddatasystems com Office controller DS1921 Z 20 ea Embeddeddatasystems com Temp sensor 920 10L1 125 Astronwireless com High gain antenna RPSM20F Antenna BBF1 Enclosure 150 Mrsolar com Field box with pole mount lock battery mount and antenna port HPMS10 22 Mrsolar com Solar panel mount SX 5M PV Panel 88 Mrsolar com Photovoltaic charge panel 8AUI Gel Battery 73 Mrsolar com Sealed lead acid 30 AmpHour battery Software The TZR and HA6 transceivers contain software in firmware that controls their hardware function including the frequency hopping that allows finding clear frequencies on which to 67 communicate even in an urban environment There is also power management software so that the devices draw very low power when not actually transmitting Operator control is conducted through a simplified language the two transceivers understand allowing all instructions to be given to them in simple ASCII text An example of this using the built in Windows application HyperTerminal is given in the instructions below However user friendly prewritten high level software is already written to accomplish all the necessary tasks re
38. eneeeeeaees 53 Figure A 2 Question and Results on Advantages of NGOGFC Use coooccnnccccococoncnonnnnanncnnncnnonannnn 53 Figure A 3 Question and Results on Disadvantages of NGOGFC Use cocooconocccoccconcncnoncconccnnnnnanoss 54 Figure A 4 Question and Results on Performance Rating for NGOGFC 1 0 eee ceeeeeeeeeeeee 54 1x Figure A 5 Question and Results on the Effectiveness of Winter Maintenance Techniques 55 Figure A 6 Question and Results of the Effectiveness of Techniques to Mitigate Black Ice 55 Figure B 1 Comparison of Permeability with Asphalt Rubber Binder ooonoccnnccnnncnnonononcnonnnnnnnos 59 Figure B 2 Comparison of Permeability with PG 76 22 Binder oooonononinccnoncnoncnnncncnoncnonccannnonnnon 59 Figure B 3 British Pendulum Number Comparison with Asphalt Rubber Binder 60 Figure B 4 British Pendulum Number Comparison with PG 76 22 Binder cece eeeeeeeeeeeee 60 Figure D 1 Thermochron embedded in asphalt pavement escceeeceeeeseeeeeeeeeesteeeeseeeenaeeees 63 Figure D 2 Installation of embedded and ambient sensors On a test section 0 0 eee eeeeeeeeeeeeee 63 Figure D 3 TZR and HA6 transceivers usina aca 64 Figure D 4 Control box and solar panel mounted on pole eee eee eeseceseceseeeeseecnaeeesaeeneeneees 65 Figure D 5 Solar radiation zones in the United States ooooonocononcnionnnoccconncconcnnnnnona nono ncnoncnnnnnnnn cons 65 Figure D 6 Diagram of a purp
39. ere questioned on the effectiveness of different methods for the mitigation of black ice on NGOGFC A copy of this question and the results are located in Appendix A as Figure A 6 Participants were asked to rate the effectiveness of the following precautions against black ice e Sanding e Liquid de icing agent e Anti icing agent e Prewetted salt e Advisory signs Respondents could answer if each of these was very effective effective moderately effective or ineffective They were also given the option of answering that they did not use a certain method at all The average rankings that respondents gave each technique are represented in Figure 2 7 Overall anti icing agents ranked as the most effective technique in mitigating black ice with an average rating of 3 43 between very good and excellent Sanding followed with an average rating of 3 40 Prewetted salts received an average rating of 3 13 and liquid de icing agents averaged at 2 86 Advisory signs again ranked lowest as an effective technique for mitigating black ice with an average rating of 1 75 15 4 3 5 aD E 3 E Sanding E 2 5 m Liquid De Icing Agent xn 2 E Anti Icing Agent 2 15 o Prewetted Salt D m Advisory Signs L 4 a 0 5 0 Maintenance Technique Figure 2 7 Average ranking of the effectiveness of techniques to mitigate black ice 2 5 3 Comparison of De Icing Use Thirteen respondents reported on how much addi
40. ery 30 minutes for 6 months at a time The data are then uploaded through a simple twisted wire pair to a palm or laptop computer Figure 3 3 shows the relative size of the Dallas Semiconductor Thermochron Figure 3 3 Dallas Semiconductor Thermochron 23 3 2 4 Hygrochron Hygrochrons are similar to Thermochrons but with an added humidity sensor and moisture permeable membrane They can measure temperature with about a 0 06 F resolution along with relative humidity Hygrochrons are self powered and logging like Thermochrons so no computer or external microcontroller is required for operation 0 Figure 3 4 shows a picture of the Hygrochron Figure 3 4 Hygrochron 3 3 Materials This laboratory experiment consists of two tests British Pendulum Tester BPT and Permeability Tests These two tests methods test two types of binders which are Asphalt Rubber and PG 76 22 with three different types of chemicals namely Matador liquid anti icing agent Freeze Guard liquid anti icing agent and Meltdown 20 solid de icing agent 3 4 Tasks 3 4 1 Permeability Permeable friction courses PFC which include new generation open graded friction courses asphalt rubber friction courses and porous European mixes PEM have gained wide acceptance throughout the southern and western portions of the United States PFC mixtures are rapidly gaining popularity because of their ability to reduce hydroplaning splash and spra
41. f America or any foreign country NOT INTENDED FOR CONSTRUCTION BIDDING OR PERMIT PURPOSES Dr Yetkin Yildirim P E Texas No 92787 Kenneth W Fults P E Texas No 38994 Preface This is the second and final report from the Center for Transportation Research on Project 0 4834 This report presents the results and findings of the information collected from the test sections for the first year of a two year project Acknowledgments This project was initiated and has been sponsored by the Texas Department of Transportation TxDOT The financial support of TxDOT is greatly appreciated The authors would like to thank TxDOT Project Director Dr Andrew Wimsatt P E for his guidance Special thanks are also extended to personnel in the Amarillo Wichita Falls and Fort Worth districts for assistance in placing pavement sensors and for everyone involved in responding to the questionnaire Products This report contains Products P2 questionnaire expanded to the national audience as Appendix A and P3 updated in situ field temperature and humidity results as Appendix C Appendix D includes all items associated with Product 7 Plans for Ice Detection Hardware List of Materials Needed including price and vendors plus a User Manual Product 7 is a standalone product CD ROM vi Table of Contents 1 Summary of Report 0 4834 2 ossiccsecescscsscessccessvvncssv eed covncesvccvstevnacsecavy copeceevcesvceuescevndesvscbytewnastes 1
42. flow control NONE File gt Properties gt Settings gt ASCII Setup Check all boxes except Force Incoming Data Click OK twice You are now connected to the TZM network via an ASCII terminal Try some commands aR 01 lt Enter gt queries network whether Thermochrons are connected responds N or P aS 01 lt Enter gt requests serial numbers of connected devices Once this is working close HyperTerminal and proceed to install Thermochron connectivity software 4 Install Thermochron Hygrochron reader software Double click on Install_1_wire msi file Uncheck box for installing COM object lower box of two 5 Select default adapter START gt PROGRAMS gt 1 WireDrivers gt Default 1 wire Net Make sure your hardware is connected and press AutoDetect If the detection process finds the adapter HA5 6 select YES to make it your default adapter If the detection process fails to find the HA5 6 driver you will need to do the following Copy the provided library file P6HAS dll to the Windows System directory and reboot your machine Repeat Step 5 6 Run Thermochron viewer software START gt PROGRAMS gt 1 WireDrivers gt One Wire Viewer htm At the top of the page click where it says Click Here The OneWireViewer screen will pop up Click on any attached device shown in the Device List to read or control it Instructions and help will be on the program screen Step 6 is all you ever need to do again once the hardware and software a
43. fy air voids less than 15 contrary to the definition of NGOGFC Twenty one percent of respondents add rubber as an additive to NGOGEFC and three fourths of this 21 of the respondents say this additive is better than other additives However 31 of respondents reported that they use cellulose as an additive and all 31 say it is better 2 7 Comments from Selected States 2 7 1 California e Caltrans OGAC Guidelines do not recommend using OGAC over unsound pavements snowy or icy areas areas with severe turning movements curb and gutter dry steering can cause the OGAC to ravel yet some of our 12 districts place it along curb and gutter with mixed results fuel or oil spill areas mill and fill areas and muddy and sandy areas eCaltrans considers OGAC beneficial to reduce wet weather accidents improve skid resistance improve wet and nighttime visibility and reduce road noise e Caltrans uses AR4000 binder PBA 6 and asphalt rubber in OGAC e Field mixing temperatures are less than 275 F for AR4000 and less than 325 F for modified binders e Tack coat rates are residual and vary from 0 01 to 0 07 gal sq yd depending on the type of surface to be tack coated e For OGAC mix design Caltrans follows California Test 368 which is available on the Internet e Conventional OGAC is the least expensive at 48 56 ton Polymer modified OGAC costs 62 77 ton Rubber asphalt OGAC costs 70 83 ton e Headquarters at Caltrans rec
44. g agents lies in their usefulness in removing snow and ice that is already bonded to the road surface However their primary disadvantages are that they cannot maintain the safest road conditions they require an application of more material than do anti icing agents and they are reactive Snowplows and tire studs are useful in northern climates with heavy snow and severe winter conditions but they cause gouging and scarring of pavement Salt may be useful only when it is applied on dry surfaces before precipitation occurs and when temperatures are lower than 14 F 6 In the event of prolonged snowing salt can be supplemented with a calcium chloride solution to remove thick ice and snow pack from spaces on the surface The use of prewetted salts and chemicals may be effective as an anti icing treatment These salts may spread more uniformly adhere better to the road surface and work faster and longer Anti icing treatments including prewetted salts and chemicals require precise timing 2 Cold Weather Performance of NGOGFCs National Survey 2 1 Introduction New generation open graded friction course NGOGFC mixes have many safety and noise benefits that are of interest to transportation engineers such as good friction lower noise reduced hydroplaning high visibility reduced splash and spray and reduced night time surface glare in wet weather conditions 7 However the early open graded friction course mixes had problems with la
45. gate Black Ice 55 Appendix B Comparison Charts 57 58 Comparison of Permeability Asphalt Rubber E Before B After Matador Freeze Guard Meltdown 20 Figure B 1 Comparison of Permeability with Asphalt Rubber Binder Comparison of Permeability PG 76 22 o o x o o o gl a Before m After Flow cm sec o o e Po o gt o o Matador Freeze Guard Meltdown 20 Figure B 2 Comparison of Permeability with PG 76 22 Binder BPN with Asphalt Rubber 45 40 35 30 25 m Before m After 20 Matador Freeze Guard Meltdown 20 Figure B 3 British Pendulum Number Comparison with Asphalt Rubber Binder BPN with PG 76 22 60 m Before m After Matador Freeze Guard Meltdown 20 Figure B 4 British Pendulum Number Comparison with PG 76 22 Binder 60 Appendix C Test Results Table C 1 Permeability Test with PG 76 22 Binder PG 76 22 Permeability __ Head Drop in 20 sec Flow cm sec Flow cm sec Flow i Atter _ Before After Change Change Ca o o70 o57_ 014 19 Matador 212 14 122 070 os 0 09 Freeze Guard 228 15 1 os 070 o 7 Freeze Guard 202 15 114 075 os os 7 3 Meow 20 27 135 135 oss 068 0 00 De icer____ Ar void Before 14 f 14 15 15
46. hermal cracking tire stud rutting gouging or scarring new construction roughness IRD clogging noise level inside vehicle or icing According to the survey respondents ranked the most important advantage of NGOGFCs as improved wet weather skid resistance and improved road marking visibility during wet weather Improved driver visibility on wet pavement reduced spray ranked in the top three On the other hand construction or initial cost of NGOGFCs was considered to be the biggest disadvantage by respondents Responses indicate that NGOGFC mixes are 22 5 more expensive than dense graded mixes Winter maintenance was ranked as the next greatest disadvantage of the PFCs The survey reveals that districts believe the most significant problems of NGOGFCs maintenance are related to NGOGFCs staying frozen longer and NGOGFC tearing shoving and pushing Among TxDOT districts the most common winter maintenance activity was identified as the use of sand during winter weather events in NGOGFC pavement areas overall anti icing agents were ranked as the most effective technique All twelve respondents indicated that they do not use prewetted salts in their winter maintenance activities on NGOGFC pavements In order to combat black ice the most commonly used method is sanding followed by advisory signs anti icing agents and liquid de icers Respondents rated the average service life of the pavements as ranging from less than six years to ten to twe
47. hing a mix temperature range for the prevention of asphalt draindown Ten 67 reported a mix temperature range above 230 F One 7 respondent reported a range of 215 to 230 F and one 7 reported a range of 200 F to 15 F Zero respondents reported using a range between 190 and 200 F and three 20 reported not knowing 2 6 3 Polymer Asphalt Binder Of seventeen respondents a majority of fifteen 88 used polymer asphalt binder in NGOGEC Only two 12 did not use polymer asphalt binder 2 6 4 Additives Respondents were asked to check all the additives used that apply Six 38 respondents reported that they use cellulose as an additive with NGOGFC Four 25 use rubber as an additive two 13 use rock fibers two 31 use other kinds of additives and another two 13 do not use any additives at all Performance with Rubber Twelve respondents reported on the performance of NGOGFC with rubber as compared to NGOGFC without rubber Three 25 reported that NGOGFC with rubber performed better and one 8 respondent reported that the performance between the two was the same Zero respondents reported that NGOGFC with rubber performs worse than with rubber and eight 67 reported that the question was not applicable Respondents then checked the indices in which rubber has the most impact if it affects performance Four 100 respondents reported that rubber impacts durability the most with 17 regard to stripping a
48. ical Report 0 4834 2 Report Date February 2007 Research Project 0 4834 Research Project Title Cold Weather Performance of New Generation Open Graded Friction Courses Sponsoring Agency Texas Department of Transportation Performing Agency Center for Transportation Research at The University of Texas at Austin Project performed in cooperation with the Texas Department of Transportation and the Federal Highway Administration Center for Transportation Research The University of Texas at Austin 3208 Red River Austin TX 78705 www utexas edu research ctr Copyright c 2008 Center for Transportation Research The University of Texas at Austin All rights reserved Printed in the United States of America iv Disclaimers The contents of this report reflect the views of the authors who are responsible for the facts and the accuracy of the data presented herein The contents do not necessarily reflect the official views or policies of the Federal Highway Administration or the Texas Department of Transportation This report does not constitute a standard specification or regulation There was no invention or discovery conceived or first actually reduced to practice in the course of or under this contract including any art method process machine manufacture design or composition of matter or any new and useful improvement thereof or any variety of plant which is or may be patentable under the patent laws of the United States o
49. in the subsequent winter season were examined for similar evidence of black ice Some appear similar to Figure 4 5 above others do not The reason is that there was no freezing or thawing that took place during the precipitation event i e there was no change of phase 4 5 Laboratory Experiment To further study the development of black ice in NGOGFCs and validate the detection methodology in the laboratory two samples were prepared from the most commonly used mix designs from the northern part of Texas These 6 in diameter specimens insulated on all sides with Styrofoam except the top to simulate field pavement and saturated at different levels were placed in a deep freezer and then frozen and thawed repeatedly to reproduce black ice formation as it occurs in the field Thermochrons and Hygrochrons were inserted at the top and the bottom of the specimens to allow for precise logging of temperature and humidity The onset depth and duration of black ice formation were recorded for each specimen De icers and anti icers were applied as well Figure 4 6 shows a picture of black ice that formed in one of the specimens Notice the plastic bag in which the specimen is placed to retain water and the wires to download the sensors data 33 wae AS k Figure 4 6 Black ice formation in one of the NGOGFC laboratory specimens To illustrate the usefulness of the sensors in the detection of black ice temperatures during the freeze thaw cycles
50. inter Maintenance of PFCs In terms of materials sand is most commonly used and is moderately effective but its small particles get lodged easily in the pavement s pores and cause clogging The use of dry solid chemicals can be effective only when there is sufficient moisture or accumulation on the pavement to prevent loss of material off a dry pavement and to trigger the solution of the salt Liquid chemicals are useful in their ability to be placed uniformly over the pavement at relatively fast spreading speeds and onto dry pavement as a prestorm treatment Liquid chemicals can be used to prevent the formation of frost or black ice However the chemical should be applied before the expected time of ice formation so that the water component of the chemical will evaporate or be removed by traffic action Traffic condition is a dominant factor only between 28 F and 35 F However liquid chemicals are not recommended for combating freezing rain or a sleet storm Liquid chemicals are more useful as anti icing agents than as de icing agents Liquid chemicals must be applied before snow has accumulated because snow keeps the chemical from reaching the pavement and may dilute the chemical For optimal efficiency liquid chemicals should be used at temperatures above 23 F However liquids can be used at pavement temperatures lower than recommended by increasing the application rate over the levels that are recommended 5 The advantage of using de icin
51. ld work were the Thermochron and Hygrochron i Buttons Fig 4 1 manufactured by Dallas Semiconductor a subsidiary of Maxim Corporation The Thermochrons measure and log temperature the Hygrochrons measure and log relative humidity 27 Thermochron j p Figure 4 1 Dallas Semiconductor Thermochron i Button The Thermochron i Button is a self contained dime sized computer and temperature sensor that is capable of logging 2 048 8 192 with the expanded model temperature readings and storing them for as long as 10 years The devices can be programmed to begin logging at a preset date and to stop at a specified second date Because of these features and because they require no external device to capture the data they can be reliably embedded in asphalt or concrete pavement at any depth The data is then uploaded through a simple twisted wire pair to a palm or laptop computer These devices have been used with great success and reliability in concrete pavements under TxDOT projects 0 1700 5 1700 1 and 5 1700 3 11 In those studies the sensors were installed before paving and used to log the relatively high temperatures found in curing concrete during summer conditions requiring an insulating coating to function in the highly alkaline and galvanic environment of fresh concrete Concurrent research Project 0 1778 12 was conducted in North Texas to measure winter temperatures at several depths in existing concrete pavement In this
52. lve years with most respondents indicating a service life of ten to twelve years In terms of design the binder grade most often used is PG 76 22 Finally permeability is not measured regularly but many respondents indicated that it is measured at the time of construction generally using the NCAT procedure the TEX 246 F method or by applying water from a water truck to check drainage 1 3 Field Work In the winter of 2004 05 the Center for Transportation Research conducted a project to test the methodology for detecting ice formation in NGOGFC pavements at three locations in North Texas The project was very beneficial for learning about the reliability of the methodology and in collecting data on black ice formation I Buttons were installed in the field and they proved to be reliable under field conditions and traffic exposure yielding an unprecedented set of highly detailed data The selection of field test sections was conducted according to the following two criteria 1 the high probability of freezing weather and precipitation and 2 the existence of permeable friction course sections Only the region of Texas north of Dallas Fort Worth routinely experiences freezing precipitation and the only existing NGOGFC pavements in this area are located in the Amarillo Wichita Falls and Fort Worth districts The Lubbock district had some NGOGEC sections in the planning stage but none were built prior to winter 2004 1 4 Recommendations for W
53. mediate spike downward in the temperature because of the phase change as the ice melts on the surface of the specimen while the bottom sensor did not evidence such phase change A similar effect can be seen when the magnesium chloride was added but it is not as prominent because of the extremely low temperature at which the de icer was added in this case Spec A placed in freezer topped with water 80 Spec B placed in freezer bottom half in water Specimen A Top 70 lA Specimen A Bottom Specimen B Bottom 60 Specimen B Top Spec A removed from freezer Spec B MgCl added Temperature F 8 Spec A MeltDown 20 added Spec B topped with water 20 120 130 140 150 160 Elapsed Time hr Figure 4 8 Temperature changes in both specimens with the application of de icing or anti icing chemicals The experiment demonstrated that the Thermochrons are able to detect ice formation and melting at various depths in the NGOGFC pavements and this validates the procedure developed for black ice detection in the experimental field sections in North Texas Furthermore this methodology can be used to detect incipient icing conditions formation of ice and effectiveness of de icing and anti icing compounds in real time as presented in the following implementation 4 6 Conclusions and Future implementation A great deal was learned both about the problem under stud
54. ment 2 5 Maintenance Respondents ranked the seven biggest maintenance challenges experienced with NGOGFC pavements with the option of indicating other maintenance issues not listed The seven possible challenges presented in the survey are the following e Pushing shoving and tearing e Slippage cracks e Stripping difficulties e Fuel or oil spills e Snowplow damage gouging and scarring e Length of frozen state e Formation of black ice 13 Among the seven possible problems three 20 respondents listed the formation of black ice as the number one most significant problem Two 13 respondents reported the most significant problem to be NGOGFCs staying frozen longer One 6 respondent reported snowplow damage gouging and scarring as the most significant problem with NGOGFCs and two 20 respondents listed other problems Zero respondents ranked pushing shoving and tearing slippage cracks stripping and fuel or oil spills as the most significant problem with NGOGFCs Fifteen 88 of seventeen respondents indicated that special activities were used on NGOGFC pavements with one 6 respondent reporting that his area conducted cleaning to restore permeability One 6 respondent reported other activities Fourteen 82 of the seventeen respondents reported that special activities were used to maintain the surface condition of NGOGFC and two 12 respondents reported that they use fog seal to maintain the surface conditio
55. n One 6 respondent reported other special activities 2 5 1 Winter Maintenance Winter maintenance techniques were evaluated by respondents they were asked to rank five techniques that they currently use from 1 ineffective to 4 very effective A copy of this question and the results are located in Appendix A as Figure A 5 The techniques presented in the survey were e Sanding e Liquid de icing agent e Anti icing agent e Prewetted salts e Advisory signs Respondents could answer if each of these was very effective effective moderately effective or ineffective They were also given the option to answer that they did not use a certain method at all The average rankings that respondents gave each technique are represented in Figure 2 6 Overall liquid de icing agents were ranked as the most effective technique with an average rating of 3 27 between very good and excellent Following were anti icing agents with an average rating of 3 13 and prewetted salts which ranked a close third with an average rating of 3 10 Sanding as a winter maintenance technique averaged at 3 00 and advisory signs ranked lowest with an average rating of 2 33 14 O Sanding m Liquid De Icing Agent fa Anti Icing Agent O Prewetted Salts m Advisory Signs Average Ranking o on Winter Maintenance Technique Figure 2 6 Average ranking of the effectiveness of winter maintenance techniques 2 5 2 Black Ice Participants w
56. nce Characteristics of Open Graded Friction Courses NCHRP Synthesis 180 Transportation Research Board 1992 5 Federal Highway Administration FHWA Manual of Practice for Effective Anti Icing Program A Guide for Highway Winter Maintenance Personnel US Army Cold Regions Research and Engineering Laboratory Corps of Engineers Hanover New Hampshire 1996 6 Huber G Performance Survey on Open Graded Friction Course Mixes Synthesis of Highway Practice 284 National Cooperative Highway Research Program Washington D C 2000 7 Yildirim Y T Dossey K W Fults and M Trevi o Winter Maintenance Issues Associated with New Generation Open Graded Friction Courses Research Report 0 4834 1 Center for Transportation Research The University of Texas at Austin 2005 8 Giles C G B E Sabey and K H F Cardew Development and Performance of the Portable Skid Resistance Tester Road Research Laboratory Department of Scientific and Industrial Research Road Research Technical Paper 66 HMSO London 1964 9 O Connor D J B Morris G W H Silcock A Methodology for the Fire Resistance Testing of Structural Components at Reduced Scale Journal of Testing and Evaluation Vol 25 No 3 1997 10 Harrigan E T Performance and Maintenance of Permeable Friction Courses Project 9 41 Burns Dennis Cooley Inc 2005 11 Dossey T S Ramaiah and B F McCullough Estimating In situ Strength of Concrete Pavements under
57. ncorrosive liquid acetate solution the use of de icing agents that are more viscous and can be retained on the surface for a longer period of time and the investigation electrostatic charge technology as a way of bonding de icing agents to the surface Three methods of cleaning clogged pavement are being used and researched in Europe and Asia a fire hose a high pressure cleaner or a specially manufactured cleaning vehicle 1 2 Survey In 2005 the Center for Transportation Research conducted an online survey on NGOGFC design maintenance performance regional practices performance ratings and in particular cold weather maintenance practices The survey was distributed online to all TxDOT districts Twenty three personnel from TxDOT districts responded to the survey of which eleven currently use NGOGFCs Nine of the twenty three respondents never used NGOGFCs and three used them in the past but have since discontinued their use Respondents were asked to rank the most important benefits of NGOGFCs According to the survey reduced splash and spray was ranked highest skid resistance and smoothness were ranked second most important followed by noise and smoothness Each benefit however received an average ranking between excellent and very good Respondents did not indicate any serious problems with NGOGFC pavements in terms of raveling in wheel paths deformation rutting potholes fat spots or bleeding stripping reflective cracking t
58. nd an increase in de icing chemicals both in Europe and the U S in general although approaches vary greatly from place to place 4 Although numerous surveys have addressed and discussed the issue of PFC winter maintenance no comprehensive or conclusive study or survey on the performance construction and design of PFCs in winter conditions has been conducted 1 1 Winter Maintenance Practices First PFCs need to have their own winter maintenance regimen with correct information on their behavior at different temperatures near or below freezing Then procedures before and after winter storms must be established including the provision of frequent specialized training to drivers of snowplows and the utilization of preventive salting or de icing chemicals Sanding PFCs to remove ice must be eliminated to keep PFCs from clogging it is not effective because small sand particles get into pavement s pores which cause clogging New technologies can also help maintain PFCs in winter conditions and help reverse damage incurred during winter conditions One avenue of research includes investigating new materials or salt alternatives for de icing roads These include prewetted salt that may stick better to the pavement surface new ways of spreading salt solutions to reduce the chance of it being washed away the use of alternatives to sodium chloride to reduce corrosion such as the two de icing agents calcium magnesium acetate CMA and Clearway a no
59. nd raveling One 25 respondent cited noise as the index to which rubber has the most impact one 25 cited smoothness and one 25 cited other indices Zero respondents cited surface friction or splash and spray Performance with Fiber Ten respondents reported on the performance of NGOGFC with fiber as compared to NGOGFC without fiber Four 40 reported that NGOGFC with fiber performed better Zero respondents reported that NGOGFCs with fiber performed the same as those without fiber and zero reported that NGOGFC with fiber was worse Four 40 respondents reported that the question was not applicable and two 20 respondents cited other answers Respondents then checked the indices in which fiber has the most impact if it affects performance Six 75 respondents reported that rubber impacts durability the most with regard to stripping and raveling One 25 respondent cited other indices Two 25 reported that they don t know and zero respondents cited surface friction splash and spray noise or smoothness 2 6 5 Tack Coat Material Fifteen respondents 88 reported using emulsion as a tack coat material with NGOGFCs and seven 41 reported using asphalt cement as a material Zero respondents reported not using any tack coat material at all Out of 15 respondents two 13 respondents reported a specified application rate of tack coat of less than 0 05 gallon per square yard Twelve 80 reported using a specified applica
60. nitor ambient conditions The ambient Thermochron is used to compare the slope of the temperature drop in the air with that in the pavement The ambient Hygrochron indicates the presence of moisture that might lead to icing The sensors working together make it possible to distinguish between rain frozen precipitation and dew The Amarillo District sections are located on SH 136 about 5 miles northeast of Amarillo The NGOGFC section is a 1 25 in thick PFC constructed in 2001 with PG 76 28 asphalt and Class B aggregate and a minimum of 18 of air voids The Wichita Falls District 30 test sections are located on US 287 near Henrietta The NGOGFC is a 1 5 in thick PFC placed in 2002 with PG 76 22 TR asphalt and 20 of air voids The Fort Worth District sections are located in Decatur north of Fort Worth in Wise County on the US 287 southbound exit ramp to FM 730 The porous pavement section was constructed in 1993 It is a 1 in thick asphalt similar to a PFC with a 20 estimated void content The embedded i Buttons were placed in each of the sections by drilling a small shallow hole in the asphalt surface along with a 2 in groove to place the twisted wires from which the data is downloaded Once the sensors were in place the hole was covered with epoxy the groove was sealed with caulk to prevent moisture intrusion from damaging the wires and to allow access to the wires for data retrieval Up to this stage of the project the data from
61. nonnnnnccnononooancononanononnncnnncnnccnnncnnnnos 40 5 3 Methodology for Remote Detection of ICiN8 ononcnnccnnnonnocononononononncnnncnoncnnnnnnnn nono n nro ncnnnnos 41 5 4 PFCs Construction and Maintenance Related to Geographic Location ooooocoocccnoncccnonnnnnns 41 A EC 43 Appendix A National Survey Questiomnaire oocom 45 Appendix B Comparison Charts sc svccesesvecssocecessesexovesesseenesosvsessesesssvenesesvenessscevecnsevsnsesstennavesaters 57 Appendix C Test Results iia ii 61 Appendix D Ice Detector Plans and User Mannual cccsscssssscssssccesssccssssccssscccssssscossssoes 63 Vili List of Figures Figure 2 1 Criteria for using NGOGFC pavements oia enon et 7 Figure 2 2 Advantages of using NGOGFC payements s esseeeseseeeeesressesresresrrsrresresseseresresseseres 8 Figure 2 3 Disadvantages of using NGOGFC pavements ocooccoccnonnconnnonnncnoncnoncnnnncnnn nono ncnnenconcnnnos 9 Figure 2 4 Service life of NGOGFC pare ment it 10 Figure 2 5 NGOGFC performance ratings disidencia dls beceeucetessucduscacesenspoens 11 Figure 2 6 Average ranking of the effectiveness of winter maintenance techniques 15 Figure 2 7 Average ranking of the effectiveness of techniques to mitigate black ice 16 Figure 3 1 British Pendulum Tester incida dit 22 Fig re 3 2 Pene ame atan aA 23 Figure 3 3 Dallas Semiconductor Thermochron essssseeseesreesessessresreesersresresseeseesre
62. ommends removing old OGAC before overlaying it with more OGAC or DGAC However some of the twelve districts are overlaying OGAC without any problem 2 7 2 Florida e Florida NGOGFC is basically a one sieve size larger aggregate paralleling Georgia work e Fibers are used to prevent draindown e Either an asphalt rubber binder or polymer modified binder is used to increase the total binder and reduce the potential for raveling and cracking e Florida is also looking at porous European FCs with thicker lift for improved reduction in hydroplaning potential which is our main reason for using OGFCs in the first place 19 2 7 3 Other States e Georgia uses OGFC primarily over SMA on interstates and for drainage where speeds exceed 45 mph e Kansas is just beginning to use PFC based on the Oklahoma and Texas experience e Kentucky has only one section of OGFC on a trial basis e Montana passed a moratorium in the 1990s against using OGFC because of stripping problems e Nevada uses OGFC with a lower void content on almost all pavements e Rhode Island uses dense 8 void content FC e Vermont has only three projects less than 2 years old 20 3 Cold Weather Performance of PFCs Lab Report 3 1 Introduction Although the more open air void range may allow water to drain more quickly it is unclear whether or not advances in PFCs will solve the problems with performance in winter conditions These open mixes may still allow accum
63. onment 3 Skid Resistance 4 Noise 5 Reduced Splash 8 Spray 1 Improved driver visibility on wet pavement reduced spray 2 Improved wet weather skid resistance 2 Improved road marking visibility during wet weather 4 Noise reduction 5 Cost 6 Durability 7 Other Figure A 2 Question and Results on Advantages of NGOGFC Use 53 11 6 2 1 5 10 1 2 15 0 3 D 0 10 at criteria are used to select an NGOGFC mixture Check all that apply Rank order 1 9 ith 1 being the most important criteria use each rank number only once at are the disadvantages of using NGOGFCs in your region Please rank 1 6 with 1 0 0 15 3 i i 5 5 General Maintenance 1 2 3 2 3 1 9 0 0 0 0 0 33 57 Feather o 0 0 0 0 4 s Figure A 3 Question and Results on Disadvantages of NGOGFC Use ow do you rate the performance of NGOGFC in your area Figure A 4 Question and Results on Performance Rating for NGOGFC 54 hat are the current winter maintenance techniques used in your region How effective are Please rate them below 2 Liquid de icer agent 3 Anti icing agent 4 Prewetted salts 5 Advisory signs 6 Other please explain below 12 24 13 27 7 14 3 Anti icing agent 4 Prewetted salt 5 Advisory signs 6 None Figure A 6 Question and Results of the Effectiveness of Techniques to Miti
64. ose built remote solar powered instrumentation DOX 66 Figure D 7 High gain YAGI antenna showing U bolt for pole mounting oocccooccnocaconacnonanannnnnnns 67 Figure D 8 Network topology for ice detection systems coooooccnonocononoccnonanonnnnncnnnnncnnncncnnnnconnaninns 70 List of Tables Table 3 1 Permeability Test Comparison Test Results Asphalt Rubber and PG 76 22 Binders a a Golapareniabereats 25 Table 3 2 British Pendulum Tester Results for Asphalt Rubber and PG 76 22 Binders 26 Table C 1 Permeability Test with PG 76 22 BIMdO Lis IA 61 Table C 2 British Pendulum Tester Test with PG 76 22 Binder 0 eee eeeeeeseeeseeeeeeeeeeeeneees 61 Table C 3 Permeability Test with Asphalt Rubber Binder eee eeeceeeeeeeeeeeeecnaeenneeseeeeeaees 61 Table C 4 British Pendulum Tester Test with Asphalt Rubber ooooococnnocccnoccccnoccccnoncccnnnccononaconns 62 Table C 5 Average Values of Permeability Test with Asphalt Rubber and PG 76 22 Binders ash ih acct A O A Suits SeSi 62 Table C 6 British Pendulum Tester Test with Asphalt Rubber and PG 76 22 Binders 62 Table D 1 Itemized Cost to Assemble One Remote Monitoring StatiON cooooonnncccnnncccnoncncnnnnnnnnns 67 Xi xii 1 Summary of Report 0 4834 2 The open graded structure of open graded friction courses OGFC draws water off the surface of the pavement which may lead to increased safety in wet weather conditions Early OGFC mixes experien
65. ower moisture susceptibility can have a lower tendency to ravel in cold climates and freeze thaw cycles The problem with PFCs is the uncertainty regarding their performance under winter weather conditions especially in rapid freezing conditions where some moisture may be trapped in the open mixes conditions that might cause black ice an extremely hazardous situation for vehicles driving at high speeds or with improper tires Some of the North Texas areas Dallas Fort Worth have reported that these mixes are the first to freeze and the last to thaw and are therefore problematic during rapidly advancing freeze conditions and especially during rapid freeze thaw cycles i e a nightly freeze with daily thaw Owing to its open graded characteristics the surface temperature of PFCs naturally tends to be several degrees lower than dense graded pavements because the high air void range makes the pavement less heat conductive at about 40 to 70 less than that of a dense graded mixture Ice and snow accumulate faster on PFC pavements because of its more open graded structure and thaw more slowly and refreeze more quickly The most serious pavement performance problems caused by winter issues are tire stud rutting gouging and scarring from snowplows and clogging According to a study done by H A Smith in 1992 European countries have much more experience with winter maintenance of PFCs Winter maintenance activities require special procedures a
66. presented in Appendix A as Figure A 1 When analyzing the results criteria that were given the rankings 1 through 4 were considered to be the most important factors in making decisions about NGOGFC use The number of respondents per criteria ranked 1 through 4 was calculated Figure 2 1 shows the results from this question Skid resistance was ranked the highest in importance by the most respondents a total of 11 Noise and reduced splash and spray were the next most important with 10 respondents each citing them as the most important criteria Finally in order of importance were traffic level 6 durability 5 smoothness 4 environment 3 cost 3 and other criteria 1 a Traffic Level Environment O Skid Resistance E Noise E Splash amp Spray m Smoothness Number of Respondents a Cost Durability Figure 2 1 Criteria for using NGOGFC pavements Criteria 2 3 2 Advantages The questionnaire asked respondents to identify the main advantages and disadvantages with the use of NGOGFC Six possible advantages were offered to respondents with the option of identifying other advantages and disadvantages not listed A copy of the question and results 1s located in Appendix A as Figure A 2 The possible advantages included the following e Improved driver visibility on wet pavement reduced spray e Improved wet weather skid resistance e Improved road marking visibility during wet weather e Noise e Co
67. problems but some countries in Europe have established winter maintenance programs to address these potential safety concerns These programs have also been implemented by some states in the U S Transportation agencies in areas subject to freezing temperatures and black ice formation have to implement winter maintenance techniques such as de icing and anti icing agents sanding and advisory signs to prevent the formation of black ice in the pavement to reduce its duration and in general to minimize the incidence of accidents under adverse weather conditions Resources for these measures have to be allocated properly meaning that those areas and pavements with a greater probability of formation of black ice such as NGOGFCs have to receive the highest priority for winter maintenance operations Researchers on this project have developed a methodology using small sensors embedded in the pavement to detect the formation of black ice The procedure has been tested in the laboratory and implemented in various NGOGFC sections in the northern part of Texas This chapter presents both the laboratory and field experiments and recommendations for a future implementation which is very promising for transportation agencies having to deal with this phenomenon 4 1 Field Work The objective of this phase of the research was to develop a methodology for studying in situ formation of black ice in permeable pavements The two types of sensors chosen for the fie
68. quired to access read and control the ice detection station A single PC with an available COM port running Windows 98 or better will control all the devices after the necessary software provided on a CD ROM is installed Step by Step Instructions In Step 1 a user will connect and test the TZR transceiver which is the base station In Step 2 you will program the TZR and one or more HA6 field transmitters to work together identifying their serial numbers to each other and setting the frequency hopping tables to run in the same order In Step 3 which is optional you will use built in Windows software to test the connectivity between all the devices At the end of Step 3 all the hardware is now talking and you will follow Steps 4 5 and 6 to install and run the i Button reading and controlling software and tell it to use the TZR and HA6 as its connection hardware This procedure is needed only to initially set up the system To use it afterwards you need only follow Step 6 If additional HA6 transceivers are added to an existing TZR base unit simply follow Step 2 again to identify the new HA6 to the TZR Up to 26 HA6 units can all communicate with a single TZR simultaneously IDs a z Up to 100 1 Buttons of mixed types can be connected to a single HA6 using a single pair of twisted wire such as is sold for burglar alarm wiring at Radio Shack However consideration should be given to this configuration if all of the devices a
69. r maintenance treatments was not enough to bring the friction properties to their initial level and a decrease in friction was observed in all cases Table 3 2 British Pendulum Tester Results for Asphalt Rubber and PG 76 22 Binders Asphalt PG 76 22 Asphalt PG 76 22 Asphalt PG 76 22 Rubber Rubber Rubber The smallest friction reduction observed was 2 with those specimens prepared with asphalt rubber and treated with Meltdown 20 a solid de icing agent Specimens prepared with asphalt rubber and treated with Freeze Guard a liquid anti icing agent showed the highest reduction in friction properties For those specimens prepared with the PG 76 22 binder the highest reduction in friction properties was observed for specimens treated by Meltdown 20 the solid de icing agent The specimens treated with the liquid anti icing agents Matador and Freeze Guard showed 18 and 14 decreases in friction properties respectively 26 4 In Situ Ice Detection Currently it is unclear whether advances in NGOGFC technology will solve the problems with performance under winter conditions These open mixes might still allow accumulations of moisture through rain snow or sleet and during rapid freezing events black ice can be produced which can be a serious concern for vehicles traveling at high speeds or with improper tire inflation or tread depth Many regions prone to snow or ice have not considered using NGOGFCs because of their potential winter
70. re on the same wiring a break or short in the cable at one location will cause some or all of the devices to be unable to communicate until the problem is repaired They will however continue to operate and record data according to how they were last programmed This data will be available for download when the wiring is repaired To set up wireless Thermochron Hygrochron system 1 Run TZR 900 Setup utility Connect the TZR to your COM port using the supplied cable Set COM port usually 1 Set Hop Table 0 Set baud rate 38 400 First scan to verify the TZR is connected properly then run Setup following the program s on screen instructions 2 Setup HA6 receivers Use HA6 900 utility provided Make up Network name set network ID 1 set COM port as in step 1 set baud rate 38 400 Add each HA6 to the table at right serial numbers are on the outside of the units First HA6 is a next is b etc up to twenty six HA6 units on one TZR transceiver Use the ADD button to add as many as you need keeping in mind there must be at least one and its address must be a Run SETUP and follow on screen instructions 3 OPTIONAL Verify hardware configuration before proceeding to Thermochron software installation and use Start gt Programs gt Accessories gt Communications gt HyperTerminal 68 Create a new connection called Thermochron select Connect using COM1 Set bits per second 38 400 data bits 8 Parity none stop bits 1
71. re set up unless you change or add HA6 units Network Connectivity Figure D 8 shows the connectivity concept for up to 2 600 i Buttons tied to twenty six field boxes 69 Figure D 8 Network topology for ice detection systems 70
72. reased by 6 On the other hand specimens treated with Freeze Guard a liquid anti icing agent and Meltdown 20 a solid de icing agent resulted in a respective 7 and 11 increase in permeability Winter maintenance treatments were unable to keep friction properties at their initial level and saw a decrease both before and after black ice formation and the application of maintenance treatments Though PFC mixtures are gaining rapid popularity concern remains as to whether the mixtures will experience performance problems that plagued the first generation While the ability of PFC mixtures to reduce hydroplaning splash and spray pavement noise improve ride quality and the visibility of pavement markings in wet weather the benefits have been outweighed by its associated inconveniences in freeze thaw environments and the increased cost of winter maintenance 5 3 Methodology for Remote Detection of Icing The methodology and equipment for detecting ice in permeable pavement have been proven in two years of lab and fieldwork and are ready for pilot implementation District maintenance offices will be able to monitor temperature and moisture conditions in instrumented pavements from a distance of up to 22 miles provided the elevation of the antennas and the topography of the area allow a satisfactory line of sight Greater distances or locations where the antennas cannot be sufficiently elevated may require a phone line or cellular connection to permit
73. s in your region Rank in order of 1 5 with 1 being the highest e Initial or Construction Cost e Winter Maintenance Problems e Durability e Performance e General Maintenance e Other SECTION 2 PERFORMANCE What is the estimated average typical service life of NGOGFC in years e lt 6 e 6 8 e 8 10 e 10 12 e gt 12 How do you rate the performance of NGOGFCs in your area in terms of the following Poor 5 Fair 4 Good 3 Very Good 2 Excellent 1 e Structural Durability i e stripping raveling etc e Surface Friction e Splash and Spray e Noise e Smoothness What is the frequency of occurrence of the following types of distresses e Tire stud rutting none low medium high e Icing none lt 5 days yr 46 gt 5 days yr Raveling lt 5 5 25 gt 25 Gouging scarring snow plow etc lt 5 5 25 gt 25 Deformation rutting none lt 0 25 low 0 25 0 50 medium 0 50 0 75 high gt 0 75 Clogging none low medium high Potholes none low lt 3 per mile medium 3 5 per mile high gt 5 per mile Fat spots bleeding none low lt 3 per mile medium 3 5 per mile high gt 5 per mile Noisy ride none low medium high Stripping lt 5 5 25 gt 25 New Construction Roughness IRI none lt 40 low 40 60 medium 60 80 high gt 80 Reflective cracking none low lt 5 47 medium 5
74. sreseeseresresss 23 Figure 3 4 LOCO a a aged a A TE 24 Figure 4 1 Dallas Semiconductor Thermochron i Button ooonoccnnncnnonononononnnonnnononcnononannnonnncnnnoo 28 Figure 4 2 Ice on CRCP Amarillo Texas ois c sssssccssdccesusdaavenasdacts coveaciaaeseceatstecatauanaeeslecdcaeasncoans 29 Figure 4 3 Phase change temperature plateaus illustrating latent heat of fusion in water 30 Figure 4 4 Snowfall event at Amarillo test section November 29 2004 c ceessceceereeeeeeeeees 32 Figure 4 5 Possible evidence of black ice in NGOGFC section in Amarillo November 2 HOA O TN 33 Figure 4 6 Black ice formation in one of the NGOGFC laboratory SpeciMenS oooococcnncccnnonncn ns 34 Figure 4 7 Example of freeze thaw cycles with black ice formation in the presence of water in one of the laboratory Simples it 34 Figure 4 8 Temperature changes in both specimens with the application of de icing or anticine chemical Siesia a E E E E ATE ange T E ORA ENTES 35 Figure 4 9 Transceivers for the wireless network eseseseseesessessresreesersesressreseeseresreseeseresreses 37 Figure 4 10 Solar panel meter and battery ss cccacecdsccccisesecavenevadi dessaeaissavadsvasgecatsseeaesedneccees secci 37 Figure 4 11 Yagi directional antenna with 22 mile range line of sight 0 00 ee eee eeeeeeeeeereees 37 Pitre 1 Texas Ae And AO a iaa 42 Figure A 1 Question and Results on NGOGFC Use ee eecceeeseeeeeneecnseceeeeseeeeaeecsaecnae
75. st e Durability Respondents were asked to rank the advantages from 1 to 7 with 1 being the greatest advantage When analyzing the results criteria that were given the rankings 1 through 3 were considered to be the most important advantages to using NGOGFCs The number of respondents per category ranked 1 through 3 was calculated Figure 2 2 shows the results from this question Improved driver visibility on wet pavement reduced spray and improved wet weather skid resistance were deemed the most advantageous by respondents with 11 respondents in each category ranking them in the top 3 Improved road marking visibility during wet weather followed with 6 respondents ranking it in the top 3 Noise reduction 5 durability 3 and cost 0 were ranked low as advantages No additional advantages were identified by the respondents Reduced Spray m Skid Resistance a Road Visibility O Noise Durability E Cost N A Number of Respondents Criteria Figure 2 2 Advantages of using NGOGFC pavements 2 3 3 Disadvantages Five possible disadvantages were offered to respondents with the option of identifying other advantages and disadvantages not listed A copy of the question and results is presented in Appendix A as Figure A 3 Possible disadvantages included the following e Initial or Construction Cost e Winter Maintenance Problems e Durability e Performance e General Maintenance Respondents
76. t of temperature and humidity at various depths The first factor evaluated the effectiveness of winter maintenance techniques on permeability and friction while the second factor evaluated the effects of repeated applications of winter maintenance techniques on the permeability and friction of PFCs Three types of instruments were used in the experiment The British Pendulum Tester BPT which measures low speed friction to access the microtexture of pavement surface the Permeameter which uses discharge through the specimen to compute the permeability of material through the velocity versus hydraulic gradient relationship and finally the Hygrochron which measures the temperature with a 0 06 degrees resolution with relative humidity BPT the British Pendulum Tester showed the highest reduction in friction properties on asphalt rubber treated with Freeze Guard a liquid anti icing agent with a 2 reduction was observed using Meltdown 20 on the asphalt rubber specimen Tests with the PG 76 22 binders showed a decrease in permeability Specimens treated with Matador a liquid anti icing agent and Freeze Guard another liquid anti icing agent showed a 15 and 16 decrease in permeability respectively Whereas the specimens treated with Meltdown 20 a solid de icing agent showed only a 3 decrease in permeability Specimens prepared with Asphalt Rubber binder showed varying results The permeability of the 40 specimens treated with Matador dec
77. tion rate between 0 05 and 0 07 gallon per square yard One 7 respondent uses an application rate of over 0 07 gallon per square yard 2 6 6 Specified Target Air Voids Out of fourteen respondents three 21 specify less than 15 air voids with NGOGFC Four 29 specify between 15 and 18 air voids another four 29 specify 18 to 20 air voids and one 7 specifies more than 20 air voids Fourteen percent specify other percentage levels of air voids with NGOGFC 2 6 7 Placement over Concrete Out of seventeen respondents fifteen 88 respondents reported that they did not place NGOGFCs over newly constructed concrete pavement Two 12 reported that they did place NGOGFC over newly constructed concrete pavement However out of twenty one respondents sixteen 76 reported not placing NGOGFC over existing concrete pavement while five 24 respondents reported that they did Respondents were asked to specify what pretreatment was used when placing NGOGFC over existing concrete pavement Four 67 reported using tack coat two 33 reported grinding one 17 reported milling and zero respondents reported using a seal coat or a rubberized seal coat Four 67 respondents reported using other forms of pretreatment zero respondents reported not using any pretreatment 18 2 6 8 Summary According to responses permeability in NGOGFC is essentially never measured let alone monitored Twenty one percent of respondents speci
78. tional de icing chemical was used in their respective areas for NGOGFCs as compared with other pavements Seven 54 reported that the usage was the same Four 31 reported that they use 25 more de icing chemical agent with NGOGFCs than with other pavements One 8 respondent stated that his area uses 50 more Zero respondents reported using 75 more de icing chemical agent with NGOGFCs 2 5 4 Winter Maintenance Cost Out of eleven respondents four 36 reported that they spend the same amount of money on winter maintenance techniques such as prewetted salts de icing agents and other items with NGOGFCs that they would with other pavements Three 27 respondents reported that they spend 25 more One 9 reported spending 25 to 50 more One respondent 9 reported spending 50 to 75 more and one 9 reported spending 75 to 100 more with NGOGFCs Only one 9 respondent reported spending less money on winter maintenance techniques with NGOGFCs than with other pavements 2 5 5 Rate of Accidents Participants were asked if they observed an increase in the rate of accidents on NGOGFC pavements Of seventeen respondents to the question zero responded yes and nine or 53 responded no Six or 35 responded that they did not know if NGOGFC pavement caused an increase in the rate of accidents or not and two respondents or 12 reported other causes for an observable increased rate in accidents on NGOGFC pavements 2 5 6 Permeabilit
79. ulations of moisture through rain snow or sleet during rapid freezing events black ice can be produced which can be a very dangerous condition for vehicles traveling at imprudent speeds or with improper tire inflation or tread depth The field portion of this study have showed that these mixes are the first to freeze and the last to thaw and are therefore problematic during rapidly advancing freeze conditions and especially during rapid freeze and thaw cycles In both Europe and the U S it has been documented that the accumulation of snow formation of ice and action of salt and de icing chemicals are different on PFC surfaces from on dense graded surfaces Because of its open graded characteristics the surface temperature of PFCs tends to be naturally several degrees lower than dense graded pavements because the high air void range makes the pavement less heat conductive at about 40 to 70 than that of a dense graded mixture Ice and snow accumulate faster on PFC pavements and thaw more slowly To evaluate the cold weather performance of PFCs samples were prepared from the most commonly used PFC mix designs from the northern part of Texas These specimens were saturated at different levels and these saturated specimens were frozen in a deep freezer to simulate black ice formation as it occurs in the field Thermochrons and Hygrochrons were inserted into the specimens to allow for precise logging of temperature and humidity at various
80. urpose built remote solar powered instrumentation box The last item to consider is the antenna for the device The standard omni directional whip antennas that come with the transceivers are unity gain and limited by their 200 ma current draw and FCC regulations to a range of approximately 6 miles This is useful for testing in the office and during assembly but probably not adequate in most situations to communicate between a distant roadway section and the TxDOT office that will monitor the equipment Fortunately a 900 MHz directional YAGI antenna is readily available for this purpose Figure D 6 The connector is the same and the antenna comes ready built with pole mounts attached This antenna will reach 22 miles if line of sight conditions are available hence the need for mounting on a pole The height required will vary depending on the topography between the test location and the monitoring office Best performance requires careful aiming of the antenna Using a handheld GPS device for pointing works fairly well but reading the RF signal strength at the receiver while the field crew in cell phone contact rotates the antenna is optimal 66 Figure D 7 High gain YAGI antenna showing U bolt for pole mounting Table D 1 gives the complete part list for assembling one remote ice detection system The unit price for the i Buttons decreases as volume goes up the price quoted is for purchasing just a single i Button Probably at least a doz
81. with and without the presence of water are shown in Figure 4 7 for one of the specimens During the first part of the experiment the sample was placed in the freezer and no water was added while the temperature dropped at approximately 43 hours water was added up to half of the height of the sample The temperature plateaus shown for the bottom sensor indicate that according to the concept of latent heat of fusion black ice formed at the bottom but not at the top of the specimen during the ensuing cycles NO WATER E 2 5 F Top g Bottom 0 0 20 40 60 80 100 120 Elapsed Time hr Figure 4 7 Example of freeze thaw cycles with black ice formation in the presence of water in one of the laboratory samples A number of state highway departments throughout the U S have decreased the use of rock salt and sand on roadways while increasing the use of liquid magnesium chloride as a de icer or anti icer This liquid chemical is sprayed on dry pavement prior to precipitation or on wet pavement prior to freezing temperatures to prevent snow and ice from adhering to the surface 34 Thus the laboratory experiment tested this substance as well as a magnesium chloride based compound manufactured by Envirotex called MeltDown 20 Figure 4 8 presents the two specimens temperatures and the changes produced by the application of the chemicals The application of MeltDown 20 causes an im
82. y and pavement noise and to improve ride quality and the visibility of pavement markings in wet weather 11 No widespread performance problems such as raveling have been reported with PFC but concerns remain whether PFC mixes will experience the same performance problems that plagued the first generation OGFC mixes used in freeze thaw environments In these environments the benefits of PFC have generally been perceived to be outweighed by the associated inconveniences and increased cost of winter maintenance and the possible related formation of glaze black ice 11 24 Permeability of the specimens in this laboratory experiment was measured after preparation of the specimens and after application of winter maintenance methods This results in the provision of information on the effect of different winter maintenance techniques on permeability 3 4 2 Friction Properties Friction properties of these specimens were measured using the BPT before and after black ice formation After that a series of remedial or maintenance strategies such as salt application and de icing chemical application were applied to these specimens These maintenance applications were repeated several times and then friction properties were measured after each cycle of application of maintenance strategies by using the BPT 3 5 Results and Analysis 3 5 1 Permeability First the permeability of the all specimens used in this project was measured The perm
83. y Monitoring Of twenty one respondents seventeen 81 reported that they do not conduct periodic monitoring for NGOGFC permeability Four 19 respondents reported that they do not know 16 if their state conducts periodic monitoring and zero respondents reported that they do conduct periodic monitoring of permeability When asked about how often permeability was measured two 22 out of nine respondents reported that they measured permeability when NGOGFCs were constructed Zero respondents reported measuring permeability every 6 months or annually Seven 78 reported other time frequencies for measuring permeability When asked how permeability was measured one 25 out of four respondents reported using the NCAT procedure The remaining three 75 respondents reported using other methods 2 6 Other Issues 2 6 1 Asphalt Content Participants were asked if the range of asphalt content was specified Out of a total of sixteen respondents eleven 69 answered yes and five 31 answered no Thirteen respondents specified a percentage rate of the asphalt content in NGOGFC Eight 62 reported an asphalt content of 5 to 7 Three 23 reported an asphalt content of 7 to 8 One 8 respondent reported a content of 9 to 10 Zero respondents reported a content of 11 to 12 and one 8 respondent reported that they did not know the asphalt content percentage rate 2 6 2 Mix Temperature Fifteen respondents reported on establis
84. y and the equipment and techniques employed to perform the study The i Buttons proved reliable under field conditions and traffic exposure and yielded information that has never been recorded in such detail before The methodology of detecting ice formation in porous pavements appears to be sound and the preliminary findings tend to agree with the opinions of TxDOT maintenance personnel revealed in the district survey results i e that NGOGFC is the first type of pavement to freeze and the last to thaw 35 A controlled study in the laboratory verified that the sensors are able to identify the heat of fusion temperature plateau effect which is the key to black ice detection this was also observed in the Amarillo field data In the upcoming stage of the project remote real time pavement temperature monitoring and ice detection will be implemented Besides the i Buttons the system is comprised of the following equipment eA point transceiver such as those illustrated in Figure 4 9 located at the base station remote location and connected to a computer eA field transceiver HA6 similar to the point transceiver but with a telephone jack to connect to wires entrenched in a saw cut in the pavement the wires are attached to the i Buttons Up to 100 Thermochrons can be connected to an HA6 Up to 26 HA6 units can be served by the point transceiver e A solar panel e A battery e A Yagi antenna for extended range The system is powere
85. y experienced thermal cracking with NGOGFCs in their respective areas Eleven 73 respondents reported that they did not experience thermal cracking with NGOGFCs 2 4 3 Relative Cost Fifteen respondents reported on the relative cost of NGOGFCs in place in their respective areas as compared with the equivalent depth of a typical ACP surface mix Three respondents 20 reported that the relative cost of NGOGFC was more than 30 more expensive One respondent 7 stated that the relative cost was 25 to 30 more expensive Five 33 reported the relative cost to be 20 to 25 more expensive Three 20 respondents reported the relative cost to be 15 to 20 more expensive Two 13 st ated it was 15 higher and one 7 respondent said the relative cost of NGOGFC was the same Zero respondents reported the relative cost to be less 2 4 4 Summary The survey respondents represented a good distribution from both icing and non icing states Fifty two percent of respondents reported an NGOGFC life span of 8 years or less and 73 reported a life span of 10 years or less States reporting the longest life span for NGOGFC were Florida Rhode Island Nevada Georgia and New Jersey with Florida and Rhode Island experiencing a life span of more than 12 years Most states are concerned with issues related to clogging and according to respondents the average relative cost of NGOGFC is 25 higher than an equivalent depth of a typical asphalt concrete pave

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