T AC User Guide to - Transportation Association of Canada
Contents
1. 7 d EU n 511 71 pu 41 1 4 PAVEMENT TEMPERATURE DENOTED AS 10 UM NU UU 1 i MM 9754 M06D mm ULL pez ms x E 1 nS A i 3 NS I i im i nam MENT TEMPERATURE DENOTED AS if m 71 3 1 x Pr H T 84 LEGEND PROBABILITY STANDARD DEVIATION VAN dn 30 o X 710 20 30 7 DAY AVERAGE MAXIMUM PAVEMENT TEMPERATURE FIGURE 9 NORMAL DISTRIBUTION CURVE 8754 09 VOLWYS264 T 2 um Me 3 3 T um 4180 HEL JO 401 p 101295 8 ON SWYAHLOSI AYNLVYSdWAL N9OIS3Q WAWINI OL 914 Saunjesadua 198014 912159 0 eq jou pjnoys pue Ajuo esodnd 20 si siu LVWGO Jo 501100 OJON LVINGOZ LVING SWH3HLOSI Junivu3adWal uiv 9534 LL2. ueipeueo uoneuuoju FIGURES VISCOSITY 60 C Pa s j 22 N O O o HEZA NN S 0 22 AWN ie m l 300 400 500 FIGURE 1 CRACKING TEMPERATURES VERSUS CGSB ASPHALT GRADE 9754 M01A PENETRATION INDEX P I j Notes 1 a aia are in M MEE MEA SS ELI during plant mixing or pavement m 0 service conditions 1 1 1441 1 1 1141 D CEE T T kN ANANA AR KR KL EE NO NI X I NA ACK ANNI RAIA P NI AINE WILL Lj ee US L P LJ Illi TETA ee 1 _ ud o eee ee ee _ LITL 2241 2 1 1 41 2 MM mild eS eee ee 40 50 60 70 80 100 150 200 500 400 50 PENETRATION 25 C mm x 0 1 FIGURE 2 CRACKING TEMPERATURES VS PENETRATION AND PENETRATION INDEX 9754 M02A BH 1 Ta x sgr 4 p m 7 2 NN a White it 1 JE l DU 128 18 DN SS
3. 1965 50 DMAT DMAT and Opmar are defined in Section 4 1 and values of these statistics may be sourced as referenced in Section 4 2 The SHRP procedure to determine the design high pavement temperature at 20 mm depth Design High in C is determined in the following manner J Determine pavement surface temperature using the following equation C 0 00618 lat 0 2289 lat 24 4 Equation 2 where lat latitude of the project site i Convert T to F using F 9 5 32 Transportation Association of Canada 18 iii Determine Design High using Design High F 0 9564 Equation 3 iv Convert Design High T 4 to Design High T using C 5 9 F 32 Transportation Association of Canada 19 5 0 TRAFFIC 51 CONSIDERATION OF TRAFFIC AND MAXIMUM DESIGN TEMPERATURE A prerequisite to undertaking selection of the asphalt binder required at the design high pavement temperature is to characterize the traffic that will use the pavement Two characteristics should be identified i e 1 operating speed H design traffic loading expressed in terms of 80 ESALs Ihree operating speeds i e loading times have been considered in developing the asphalt binder selection methodology presented in this Guide These speeds are 100 km h 50 km h and 20 km h for which corresponding pavement loading times are 0 01 seconds 0 02 seconds and 0 05 seconds
4. defined in Section 4 1 for the Canadian weather stations included in the SHRP database have been used to develop high air temperature isotherms at intervals at 5 C This Figure should be used for information purposes only It should not be used as a substitute for determining more precise site specific information 43 SELECTION OF THE DESIGN LOW PAVEMENT TEMPERATURE TAC provided following guidelines that are to apply to the methodology for selection of the design low pavement temperature I pavement temperature at surface as estimated from air temperature is to be used 1 the SHRP Superpave air temperatures are to be used li the method for estimating pavement surface temperature is to based on previous work of other researchers and is to recognize temperature correlations that are available from existing Canadian test roads including the three C SHRP sites Pavement temperatures in the winter are known to be warmer than prevailing air temperatures Pursuant to completion of an analysis to correlate air and pavement surface temperature data at Canadian test road sites the following equation has been adopted to determine design low pavement temperature at the 98 percent probability level 1 98 percent probability that the design low pavement temperature will not be exceeded Design Low C 0 859 T 20 1 7 C Equation 1 and 4 are defined in Section 4 1 and values of these sta
5. 6 0 Select the Optimum CGSB Asphalt Cement Where Thickness is 526 mm See Step 6 2 M2 D 206 Pen Group XC ii Specify Alternative Binder R9754M12G FIGURE 12 FLOW CHART FOR SELECTION OF ASPHALT BINDER Project Identifler EXAMPLE 3 ats SANE 29 Define Traffic Parameters 2 Level 22 Chapter 5 Operating Speed Level 2 2 ESALs 2 0 3 0 Determine Design Low and High Air Temperatures 3 1 Low Air Temperature 3 2 High Temperature Chapter 4 Chapter 4 225 C 2 2 DMAT _3 _s ODMAT _ 33 Risk Analysis Chapter 4 i Design Low Te 2 Ow 2X c Design High DMAT C _ 2 _ODMAT 2H L C Calculate Design Low and High Pavement Temperatures 41 Design Low 42 Design High Pavement Temperature Pavement Temperature SHRP Database or SERO Safety FactorXa C Chapter 4 4 Equations 2 amp 3 5 2 identity Candidate identify Candidate CGSB Ke CGSB Asphalt Cements Figure 6 7 or 8 phare Pen Group ___ Group U ____ Pen Group ____ 60 Select the Optimum CGSB Asphalt Cement Where Thickness is__ SeeStep6 2 Pen Group Specify Alternative Binder ML m R9754M12G FIGURE 12 FLOW CHART FOR SELECTION OF ASPHALT BINDER TABLE
6. 0 CAN CGSB 16 3 M90 Asphalt Cements for Road Purposes Transportation Association of Canada Association des transports duCanada The overall mission of the Transportation Association of Canada TAC 1s to promote the provision of safe efficient effective and environmentally sustainable transporta tion services in support of the nation s social and economic goals To this end TAC acts as a neutral forum for the discussion of transportation issues serves as a technical focus in the field of roadway transportation promotes R amp D activities and disseminates transportation related information pub lished by TAC and others The role of TAC s Research and Development Council is to foster innovative efficient and effect re search and technology transfer in support of Canadian transportation This project was conducted as part of the Council s co operative reserach program with funding provided by the federal provincial and ter ritorial ministries of transportation La mission de l Association des transports du Canada ATC est de promouvoir la s curit l efficience l efficacit et le respect de l environnement dans la prestation de services de transport en vue d appuyer les objectifs sociaux et conomiques du pays A cette fin J ATC offre une tribune neutre pour la discussion des enjeux et des probl mes li s aux transports sert de cen tre d tudes techniques dans le domaine des transports routiers enco
7. Transportation Association of Canada 2 not contain specifications for any types of enhanced binders and it is beyond the scope of this Guide to provide guidelines for their selection Full documentation of the research that led to the development of this guide is contained in the report Characteristics Performance and Selection of Paving Asphalts referred to throughout the User Guide as the TAC Report That report also contains discussion of developments under the Strategic Highway Research Program SHRP and the Canadian counterpart C SHRP The Guide user should reference the TAC Report for details which are beyond the scope of the Guide Transportation Association of Canada 3 1 0 INTRODUCTION 11 BUT DU PRESENT GUIDE Une norme nationale du Canada intitul e Liants bitumineux pour les routes CAN CGSB 16 3 M90 a t pr par e par l Office des normes g n rales du Canada CGSB La norme actuelle est le r sultat de plusieurs ann es de travaux men s par un groupe de sp cialistes canadiens de la technologie des rev tements bitumineux L Association des transports du Canada ATC a compris que l utilisation de la norme actuelle serait plus facile s il existait un guide de s lection des liants bitumineux La s lection d un type de liant bitumineux en fonction d un rev tement particulier parmi les diff rents produits mentionn s dans la norme rel ve bien entendu de plusieurs param tres li s au projet L util
8. During asphalt plant mixing initial hardening of the asphalt cement occurs and the age hardening process continues during the service life of the pavement As a result rheological properties that influence low temperature pavement performance i e low temperature properties are not the same as for the original asphalt cement This must be recognized in the asphalt cement selection process to ensure that satisfactory pavement performance results This may be accomplished by incorporation of a safety factor to further reduce the design low pavement temperature Equation 1 Chapter 4 3 Robertson 1987 used a value of 10 C to at least in part account for the age hardening factor A 10 C safety factor should be used in the asphalt selection procedure outlined in Chapter 7 0 unless a Canadian agency has sufficient experience to warrant use of an alternate safety factor value The user should review the Final TAC Report Section 6 3 4 for further explanation in respect to aging of CGSB asphalt cements 6 2 AGGREGATE SELECTION FOR PAVING MIXTURES It is beyond the scope of this Guide to identify the detailed properties required of aggregates that should be used for each traffic level and operating speed condition The designer of paving mixtures may refer to the SHRP Superpave Mix Design Manual for guidance in this regard As Transportation Association of Canada 22 well previous experience with locally available aggregates may provide an
9. F Transportation Association of Canada 26 Step 5 Step 6 Identify Candidate Asphalt Cements 5 1 5 2 For Design Low Pavement Temperature Using the design low pavement temperature adjusted colder by the 10 C Safety Factor in Step 4 1 as the pavement cracking temperature refer to Figure and record those candidate Group A B or C asphalts by penetration grade where the cracking temperature isotherm intersects the lines that represent the specification boundaries for each penetration grade specified in the CGSB standard For Design High Pavement Temperature Using the design high pavement temperature as determined in Step 4 2 and the design or legislated operating speed determined in Step 2 2 enter Figures 6 7 or 8 Identify the horizontal line that represents the operating speed for the project and proceed to the right to its intersection with the dashed line that most closely represents the design high temperature value Interpolation between design temperature lines is a valid procedure Identify and record those penetration grades of asphalt cement i e the labelled solid lines that lie to the right hand side of the intersection of the operating speed design pavement temperature intercept If an intercept point occurs on that part of a design pavement temperature line that is shown in dot legend i e not the dashed portion then this means that there is no CGSB Group A B or C asphalt cement that meets the required
10. These vehicle operating conditions are similar to those that are used by SHRP in the Superpave mix design process Figures 6 7 and 8 have been developed on the foregoing basis Asphalt binder requirements for other prevailing operating speeds may be interpolated in Figures 6 7 and 8 Design traffic loading expressed in cumulative ESALs over the design life of the pavement structure influences the binder selection process in the manner presented in Section 7 0 Three traffic levels are provided in Superpave and have been selected for utilization in this Guide i e Design Design Level 80 kN ESALs 1 Low 10 2 Intermediate 105 10 3 High gt 10 The influence of design traffic is predominantly provided for by specifying requirements of the mineral aggregate gradation particle shape texture fracture etc In high and intermediate design level cases the coarse aggregate fraction should be of the maximum practical nominal Transportation Association of Canada 20 size and should consist of 85 percent or more of particles with two or more fractured faces The fine aggregate fraction should be of high angularity Selection of the most appropriate asphalt binder from those alternatives that may satisfy the maximum design pavement temperature requirements is a function of the design traffic level and is described in Section 7 0 In principle for low traffic volumes Design Level 1 the softest penetration grade t
11. 13 CONTENTS OF THE USER GUIDE TN 10 INTRODUCTION 11 BUTDU PRESENT GUIDE 12 PARAM TRES DE S LECTION D UN LIANT BITUMINEUX 13 CONTENU DU 44 4 1 0 0 nennen nnn nnne enn 90 16 3 1 90 2 nnne nn tranne nnne tenen enne enne nennen 30 PAVEMENT DISTRESS TYPES AND THEIR MITIGATION 31 BACKGROUND con roe 3 2 LOW TEMPERATURE CRACKING 33 PERMANENT DEFORMATION 34 FATIGUE 3 5 MOISTURE SENSITIVITY AND STRIPPING M n 3 6 AGING OF THE SYSTEM 3 7 DURABILITY 40 SELECTION OF DESIGN PAVEMENT TEMPERATURES 41 INTRODUCTION 42 SOURCE OF CANADIAN TEMPERATURE DATA 43 SELECTION OF THE DESIGN LOW PAVEMENT TEMPERATURE 44 SELECTION OF THE DESIGN HIGH PAVEMENT TEMPERATURE 50 TRAFFIC 51 CONSIDERATION OF TRAFFIC AND MAXIMUM DESIGN TEMPERATURE T EE 52 CONSIDERATION OF TRAFFIC AN D MINIMUM gt DESIGN TEMPERATURE 60 OTHER CONSIDERATIONS 61 SAFETY FACTORS 6 2 AGGREGATE SELECTION FOR PAVING MIXTURES 63 PERFORMANCE TESTING OF PAVING MIXTURES enn 6 4 LIMITATIONS aoo 237 sed 70 THEASPHALT CEMENT SELECTION PROCEDURE 7 1 BACKGROUND 72 STEP BY STEP PROCEDURE 73 WORKED EXAMPLES TABLES TABLE OF CONTENTS FIGURES NRE FARI E i a b
12. Report Date IRRD No Project January 1996 1316 Project Manager Christopher Hedges Title and Subtitle TAC User Guide to CAN CGSB 16 3 M90 Asphalt Cement for Road Purposes Author s Corporate Affiliation s Cece Dawley EBA Engineering Bert Pulles Sponsoring Funding Agency and Address Performing Agencies Names and Addresses EBA Engineering 14535 118 Avenue Edmonton AB T5L 2M7 TAC R amp D Council 2323 St Laurent Blvd Ottawa ON K1G 4K6 Abstract Keywords IRRD Bituminous mixture Design overall design Selection Specifications Guidance Traffic count Weather Durebility Properties Canada The purpose of this study was to document a set of procedures for the selection of paving asphalts based on the Canadian General Standards Board CGSB 1990 specification Asphalt cements for road purposes CAN CGSB 16 3 M90 This specification was published in 1990 and was intended to serve as a national standard for asphalt cements While the Strategic Highway Research Program has more recently produced new performance based binder specifications several Canadian jurisdictions have indicated their intention to continue using the CGSB penetration grades for some time into the future A User Guide to accompany the CGSB specification was never published although a number of draft versions were developed It was recognized by TAC
13. indication of their suitability for similar uses in the future 63 PERFORMANCE TESTING OF PAVING MIXTURES The purpose of this Guide is to provide the user with guidelines to select the most appropriate asphalt binder for an asphalt paving mixture on a project specific basis Beyond this point the procedure for developing the job mix formula on the basis of laboratory trial mixtures require methodologies that are beyond the scope of this Guide In this regard key properties of paving mixtures that should be considered are related to aggregate and mixture volumetric properties Laboratory testing programs exist that can assess the probable performance of candidate paving mixtures in respect to permanent deformation fatigue durability and moisture sensitivity and stripping The Guide user should refer to the TAC report for further information in this regard 6 4 LIMITATIONS CAN CGSB 16 3 M90 contains specified requirements for asphalt cements for road purposes that are applicable to Canadian conditions Using the asphalt binder selection procedure that is provided in Section 7 0 of this Guide the user may occasionally identify requirements for asphalt binder that cannot be provided by conventional asphalt cements that are available in this Standard Hence the continuing use of the term asphalt binder in this Guide The user may have to look to other sources such as polymer modified asphalts or specially engineered asphalts to fulfil som
14. is to be mitigated at the 98 probability level To satisfy low temperature requirements a 120 150 A or B Grade or softer and some C Grades are suitable However for high temperature considerations the A Grade that may be acceptable requires extrapolation of curves on Figure 6 is harder than 80 pen In this instance it would be preferable to select some premium asphalt Transportation Association of Canada 32 ame Project ate EXAMPLE 1 Define Traffic Parameters 21 Traffic Level 22 Chapter 5 Operating Speed Level_L_ _ amp 0 __ESALs ADD 3 0 Determine Design Low and High Alr Temperatures 31 Air Temperature gt 32 High Temperature Chapter 4 Chapter 4 Tar 6 _2 3 DMAT 22 5 2 4 33 Risk Analysis Chapter 4 i Design Low Z _ One 45 8 Design High 2 22 pre Calculate Design Low and High Pavement Temperatures Design Low 42 Design High Pavement temperature Pavement Temperature Chapter 4 and Chapter 6 1 Safety Factors SHRP Database or 316 Safely Factor ot Chapter 4 4 227 24 3 54 Identify Candidate Identify Candidate CGSB jode d CGSB Asphalt Cements 6 7 or 8 200 HOD Pen Group SA _ 200 Group 50 ZAQ Pen Group _ Group ____ Select the Optimum CGSB Asphalt C
15. properties at the design high temperature end of the spectrum Select the Optimum Asphalt Cement Three possibilities exist at this point These are defined below and an appropriate final step is described in each case I One or more CGSB asphalt cements exist in both the lists prepared in Step 5 1 and Step 5 2 i e there is more than one product that satisfies both design temperature conditions In this situation the Guide user should consider the significance of the selected product upon permanent deformation and fatigue as discussed in Chapter 3 This is done by reviewing preferred Transportation Association of Canada 27 paving mixture and asphalt cement stiffness requirements as a function of traffic level and pavement thickness using the following matrix Traffic Pavement Thickness T pavement Level ee lt 125 mm gt 125 mm 1 Low low viscosity high viscosity 2 Intermediate user discretion high viscosity 3 High not normally high viscosity applicable 11 One or more CGSB asphalt cements will satisfy each of the two design temperature conditions but none will satisfy both In this situation the Guide user should re consider the risk analysis that was undertaken as part of Step 3 In the Canadian climate environment it is not normally desirable to knowingly increase the risk of incurring low temperature pavement cracking by selecting a design cold air temperature than is warmer than Tiir 20 Chapter 4
16. un liant Climat bitumineux en vue d un projet particulier d apr s la seule norme CGSB n est pas une t che simple Durabilit Par cons quent l ATC a fait pr parer le pr sent guide d utilisation comme compl ment de la Caracteristiques norme CGSB en fonction des meilleures connaissances actuelles relatives 1 au climat canadien Canada 2 aux sources et aux caract ristiques des bitumes utilis s au Canada 3 aux donn es canadiennes sur le rendement des rev tements 4 aux normes et m thodes d essai provinciales actuelles se rapportant aux bitumes 5 l effet probable des r sultats du programme strat gique de recherche routi re se rapportant aux bitumes et 6 l utilisation des bitumes de qualit sup rieure et des bitumes modifi s par des polym res Le guide d utilisation doit servir de compl ment de la norme CGSB et il d crit m thodiquement les tapes avec exemples l appui de la s lection des bitumes pour tout projet de rev tement ex cut au Canada compte tenu des conditions climatiques et de la densit de la circulation 11 existe galement un rapport final d taill qui contient une documentation compl te sur les recherches ayant men la pr paration du guide d utilisation Afin de faciliter la s lection des rev tements on a extrait de la base SHRPBIND des donn es sur les temp ratures minimales et maximales signal es par les stations m t orologiques canadiennes donn es qui sont galement
17. However it may be acceptable to compute the design high pavement temperature on the basis of rather than DMAT 10DMAT 20DMAT especially if Traffic Levels 1 or 2 have been estimated That is to say the Guide user assesses whether some increased risk of permanent deformation rutting can be tolerated in order to accommodate selection of a CGSB asphalt cement Hi or more CGSB asphalt cements will satisfy the low design pavement temperature requirement but none will satisfy the high design pavement temperature requirement at the prevailing operating speed In this situation the Guide user has two fundamental options i e Ignore the risks that are associated with either the design low or high pavement temperature condition and select that CGSB product that is the best compromise not recommended or Specify an alternative asphalt binder that will meet the service temperature requirements Alternative products may include polymer modified asphalt or other types of enhanced binders Transportation Association of Canada 28 73 WORKED EXAMPLES The following examples demonstrate some of the basic possibilities that the Guide user may encounter as identified in Step 6 of the above selection procedure Flow Charts that have been used to complete the selection process are provided following the examples Example 1 The project is located on a provincial highway in western Canada The highway trave
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19. Tyavement C 0 859 Tair 20 1 7 Equation 1 If the risk analysis undertaken in Step 3 determines that the 98 percent probability level i e 20 is excessive adjust 10 or delete the 0 factor to suit the selected risk factor i e 84 percent or 50 percent Transportation Association of Canada 25 A Safety Factor of 10 C should be applied to the design low pavement temperature determined from Equation 1 To clarify the value of Design Low T pavement C should be reduced an additional 10 C as explained in Section 6 1 4 2 Design High Pavement Temperature I _ Select the value of T on the basis of acceptable risk level probability from the following tabulation Probability Value of T 98 20 84 10 50 DMAT Refer to the source referenced in Chapter 4 for values of DMAT and ii Determine pavement surface temperature from Equation 2 Tur C 0 00618 lat 2 0 2289 lat 24 4 Equation 2 where lat latitude of project in degrees HD Convert from C to F using F 9 5 32 iv Determine Design High from Equation 3 Design High in F 0 9564 T Equation 3 v Convert Design High 70 F to Design High T C using C 5 9 F 32 It is important to note that Equations 2 and 3 as currently issued by SHRP require the user to convert temperatures C to and from
20. VILWFSZ 6H 5 seunjgjedue 128 014 pesn eq jou pjnous pue Ajuo esodnd 20 si SI TTE Project Identifier 29 Define Traffic Parameters 21 Traffic Level 22 Chapter 5 Operating Speed Level U U l ESALs a 3 0 Determine Design Low and High Air Temperatures 3 1 Low Alr Temperature High Temperature Chapter 4 Chapter 4 Tam CS ODMAT 3 3 Risk Analysis Chapter 4 i Design Low lt ___ ___ lt ij Design High T C ____ ODMAT Design Low and High Pavement Temperatures 4 1 Design Low 42 Design High Pavement Temperature Pavement Temperature wns Seer SHRP Database or Chapter 4 4 Equations 2 amp 3 Safety Factor__ C 5 1 identify Candidate identify Candidate CGSB Asphalt Cements CGSB Asphalt Cements Figure 1 Figure 6 7 or 8 ____ ____ Pen Grup G gt Pen Group Pen Group ____ 6 0 Select the Optimum CGSB Asphalt Cement Where Thickness is mm See Step 6 d Pen Group Specify Alternative Binder ______ FIGURE 12 FLOW CHART FOR SELECTION OF ASPHALT BINDER R9754M12G
21. a v 3 CE Pa 1 k 5 x k a L 2 ew C CURT ee i 1 0 INTRODUCTION 1 1 THE PURPOSE OF THIS GUIDE A National Standard of Canada for Asphalt Cements for Road Purposes has been developed as CAN CGSB 16 3 M90 by the Canadian General Standards Board CGSB The current standard is the product of several years of development by a group of leading Canadian experts in asphalt paving technology The Transportation Association of Canada TAC recognized that utilization of the current Standard may be enhanced through development of a User Guide intended to describe how the asphalt cement selection procedure should be conducted Selection of the grade and group of asphalt cement for an asphalt concrete pavement on a project specific basis from the alternative products that are available in the Standard is appropriately dependent upon several project related factors The purpose of this Guide is to provide the user with a logical step by step procedure to enable the most appropriate grade and group of asphalt cement to be chosen in consideration of these factors Methodology for identifying and addressing these factors in the asphalt cement selection process is provided in following Sections The methodology specifically addresses selection of conventional asphalt cements for new pavements Asphalt cement selection for overlay p
22. ame principles apply for probability consideration for the low temperature design case 4 2 SOURCE OF CANADIAN TEMPERATURE DATA The SHRPBIND Version 2 0 program includes a database of 1800 Canadian weather stations A copy of the Canadian data is available from TAC at the following address Transportation Association of Canada 2323 St Laurent Boulevard Ottawa Ontario Canada K1G 4K6 Telephone 613 736 1350 Fax 613 736 1395 For more information about the SHRPBIND program contact Mr Monty Symons Pavement Performance Divisin NHR 30 U S Federal Highway Administration Turner Fairbank Highway Research Center 6300 Georgetown Pike McLean Virginia 22101 2296 FAX 703 285 2767 Climate information is available at Environment Canada offices throughout Canada Table 1 shows the addresses and current 1995 telephone numbers of some regional and local Environment Canada offices Figure 10 is presented to illustrate the cold air temperature regime in Canada Values of Tar 20 as defined in Section 4 1 for the Canadian weather stations included in the SHRP database have been used to develop cold air isotherms at intervals at 5 This Figure should be used only for information purposes and should not be used as a substitute for determining more precise site specific information Transportation Association of Canada 16 Figure 11 is presented to illustrate the hot air temperature regime in Canada Values of DMAT 20
23. as been described in the TAC Final Report 92 4 Vol 1 to control traffic induced permanent deformation of asphalt pavements under high seasonal temperature conditions The methodology is based on concepts which include I The critical stiffness modulus i e relationship between stress and strain as a function of time of loading and temperature of a compacted paving mixture at 40 C is 2 38 x 108 N m ii relationship exists between paving mixture stiffness at 40 C and the minimum stiffness which the asphalt cement should exhibit at that temperature if the asphalt cement is to serve its contributory role in mitigating permanent deformation iii The critical stiffness of initially aged after plant mixing conventional asphalt cement 15 5 0 x 10 N m at 40 C if the mineral aggregate in the paving mixture possesses excellent angularity properties and is 1 0 x 10 N m at 40 C if the mineral aggregate is of poor angularity The critical stiffness value of 5 0 x 10 N m for initially aged asphalt translates to a limiting stiffness of approximately 1 5 x 10 N m for asphalt in its original as delivered condition Figures 3 4 and 5 illustrate stiffness properties of CGSB Group A B and C asphalts respectively at various loading times in their original as delivered condition In principle Transportation Association of Canada 11 to mitigate permanent deformation at the prevailing operating speed it is necessary to sele
24. ct an asphalt cement if available that possesses the critical stiffness properties defined above and to specify aggregates that exhibit excellent angularity properties To this point methodology which has been described to determine asphalt stiffness at elevated temperatures under a range of loading times is based on long established conventional technology Some members of the TAC Steering Committee have suggested that on the basis of Canadian experience nomographic solutions from Figures 3 4 and 5 are too conservative i e softer asphalts are regularly used than would be specified using those Figures The Report describes a concept which has evolved recently and which was made possible using SHRP asphalt binder specifications and testing protocols This initiative has enabled a series of design pavement temperature isotherms to be superimposed onto Figure 3 4 and 5 to create Figure 6 7 and 8 respectively for each of Group A B and C asphalts The method of proposed use of Figures 6 7 and 8 for selecting the appropriate asphalt cement for the high pavement design temperature condition is described in Section 7 0 Step 5 2 3 4 FATIGUE Two types of fatigue distress thermal and structural can develop within an asphalt concrete pavement structure Thermal fatigue results from repetitive thermal cycles but the process is not well understood and is not further referenced Structural fatigue cracking usually occurs when a pavem
25. d by mixture and compaction qualities achieved during Transportation Association of Canada 13 construction by the air voids in the compacted pavement and by the thickness of asphalt film provided on the aggregate particles within the mixture Durability properties are less significantly influenced by the grade of asphalt selected than by matters associated with asphalt ageregate compatibility and by the paving mixture design process Transportation Association of Canada 14 4 0 SELECTION OF DESIGN PAVEMENT TEMPERATURES 41 INTRODUCTION SHRP has created a weather database that contains temperature statistics for approximately 1850 weather stations in Canada The database is contained within the Superpave Binder Selection Program SHRPBIND Version 2 0 May 1995 Location information includes station names province or territory longitude latitude and elevation of each station and the following relevant temperature information I DMAT which 15 the design maximum air temperature and is the average of at least ten years of yearly maximum air temperature YMAT and YMAT 1 defined as the yearly maximum 7 day floating average of the daily maximum temperatures 1 Which is the standard deviation of at least ten years of YMAT T which is the average of at least ten years of the annual coldest air temperature IV which is the standard deviation of Tir Within the TAC Report descriptions are pro
26. diffus es s par ment par l ATC Nombre de pages Nombre de figures Langue Anglais Renseignements suppl mentaires Acknowledgements This project was conducted with funding provided by TAC s Research and Development Council TAC would like to express its appreciation to the members of the project steering committee who volunteered their time to provide advice guidance and direction TAC would also like to thank all those individuals and agencies who contributed to the success of the study by responding to survey questionnaires Project Steering Committee David Haughton Chairman Daryl Macleod B C Transportation amp Highways Saskatchewan Department of Highways and Transportation Imants Deme Shell Canada Products Limited Lyle Moran Imperial Oil Ltd Research Department Keith Foster Nfld Dept of Works Services amp Dave Palsat Transportation AGRA Earth amp Environmental Chuck Juergens Kai Tam Husky Oil Marketing Company Ministry of Transportation Ontario Anne Marie Leclerc Christopher Hedges Project Manager Minist re des Transports du Qu bec Transportation Association of Canada Principal Consultants Cece Dawley EBA Engineering Consultants Ltd Bert Pulles In Memoriam John Corkill 1930 1993 d E se LES Aa 1 0 INTRODUCTION 11 THE PURPOSE OF THIS GUIDE 12 THE CONCEPT FOR SELECTION OF THE ASPHALT CEMENT die
27. e cracking Example 2 The project involves construction of a passing lane on a rural highway that will be subjected to loaded logging and chip trucks operating at a speed of 80 km h or less The design traffic level is Intermediate gt 10 ESALs lt 107 The total design pavement thickness 15 150 mm The SHRP database contains the following relevant statistics at a nearby weather station Latitude 51 Elevation 500 m Average Annual Coldest Air Temperature Tair 30 C gair Average Yearly Maximum Air Temperature DMAT 34 C oDMAT 2 C Following jurisdiction policies exist is respect to risk for pavement design for Travel Level 2 designs Low temperature cracking is to be mitigated at the 98 probability level low pavement temperature safety factor of 10 C applies Permanent deformation is to be mitigated at the 98 probability level Transportation Association of Canada 30 The candidate asphalt cements identified in Step 5 1 on the accompanying Flow Charts are the lowest pen Group products that may be used The candidate asphalt cements identified in Step 5 2 are the highest penetration Group products that may be used The CGSB penetration grade Group products are then For Low Temperature For High Temperature 150 200 Group A 150 200 Group A or harder 200 300 Group A or softer Thus a 150 200 Group A asphalt should be selected as suitable for this project A compromise solution
28. e project specific requirements Transportation Association of Canada 23 7 0 THE ASPHALT CEMENT SELECTION PROCEDURE 7 1 BACKGROUND A detailed step by step procedure is provided in this Section to enable the Guide user to identify from those candidate materials which are found in CAN CGSB 16 3 M90 that asphalt cement that is optimum for use on a project specific basis 7 2 STEP BY STEP PROCEDURE The step by step asphalt cement selection procedure is illustrated in Figure 12 which may also be used as a Worksheet for performing the analysis Each step is discussed below Step 1 the Project provide highway or street identification and the terminal start and stop points Determine latitude longitude and elevation of project Step 2 Define the Traffic Parameters 2 1 Design Traffic Refer to Chapter 5 Information on heavy traffic ESALs is normally available from traffic engineering personnel within the highway or street agency In the absence of available data from such sources ESALs may be estimated using the following equation ESAL AADT HVDF TDY where ESAL Equivalent Single Axle Loads per Lane Year AADT Average Annual Daily Traffic all lanes both directions HVP Heavy Vehicle Percentage divided by 100 HVDF Heavy Vehicle Distribution Factor percent of heavy vehicles in the design lane NALV Number of equivalent axle loads per vehicle Truck Facto
29. ement Where Thickness is mm See Step 6 2 200 Group A I i Specity Alternative Binder FIGURE 12 FLOW CHART FOR SELECTION OF ASPHALT BINDER R9754M12G Project Identifier CC Qe S ES From LE To AL la Long Low 25 60 High Jait EXAMPLE 2 Detine Traffic Parameters 21 Traffic Level 2 2 Chapter 5 Operating Speed Level 2 AO ESALS Q Kmi 30 Determine Design Low and High Air Temperatures 3 2 High Temperature Chapter 4 24 s 2 C 31 Low Air Temperature Chapter 4 ais C Our 2 Risk Analysis Chapter 4 i Design Low Tir u acc Z 5 ii Design High DMAT C 2 2 C 4 0 Calculate Design Low and High Pavement Temperatures 4 2 Design High 4 1 Design Low Pavement Temperature Chapter 4 3 1 and Chapter 6 1 Safety Factors 23 20 Safety Factor M Use 2 Pavement Temperature SHRP Database or Chapter 4 4 Equations 2 amp 3 5 1 Identify Candidate Identify Candidate CGSB Asphalt Cements CGSB Asphalt Cements Figure 1 Figure 6 7 or 8 i 0 Zoo Pen Group _Q_ 9 AG Zor Group ii Zec 406 Group A ____ Pen Group iii 2 C C 460 Group G ii _____ Pen Group
30. ent is stressed to the limit of its fatigue capacity by repetitive loads or when loads are applied that exceed the capacity of the pavement structure Predominant paving mixture properties that influence fatigue related performance include I excessively stiff asphalt cement i deficient asphalt cement content To mitigate structural fatigue cracking following guidelines have been proposed when the total asphalt concrete layer thickness is less than 125 mm paving mixtures of low stiffness i e low viscosity asphalt cements are preferred when the total asphalt concrete layer thickness is greater than 125 mm paving mixtures of high stiffness i e high viscosity asphalt cements are preferred Transportation Association of Canada 12 In the actual asphalt cement selection procedure described in Section 7 0 methodology is provided for considering pavement fatigue issues when more than one alternative asphalt cement is available that satisfies both low and high service temperature requirements i e transverse cracking and instability rutting 3 5 MOISTURE SENSITIVITY AND STRIPPING Stripping of the asphalt film from the aggregate occurs when there is loss of adhesion between the aggregate surface and the asphalt cement and 1 primarily due to the action of water This problem is essentially one of aggregate asphalt cement compatibility and is normally resolved by incorporation of an anti stripping agent into the asphalt mix P
31. erformance tests are normally performed in the laboratory to determine stripping potential and the effectiveness of such admixtures in limiting its occurrence Stripping potential does not appear to be directly related to the penetration grade or group of asphalt cement selected but it is related in a complex physical and or chemical manner to the interaction between the asphalt and aggregate forming the paving mixture 3 6 AGING OF THE ASPHALT AGGREGATE SYSTEM Aging or age hardening of the asphalt cement in an asphalt paving mixture is the change in the rheological properties viscosity penetration that occurs during the plant mixing and placement operation and that continues during the service life of the pavement The aging process can be controlled by ensuring that suitable volumetric properties of the paving mixture are provided during the mix design process and that proper plant mixing and compaction practices are followed during construction However it is important to be aware that selection of the best quality of asphalt cement that is available in the CGSB Standard will have positive effects on the pavement quality if all other design and construction practices are properly undertaken 3 7 DURABILITY Durability of an asphalt pavement refers to its competence to maintain structural integrity under operating conditions i e under the influence of traffic moisture and freeze thaw Durability of a compacted pavement is influence
32. ermine the Penetration Index PI of the asphalt cement It should be recognized that the CGSB Standard does not specify penetrations 100 g 5 sec at more than one temperature A procedure for determining the minimum pavement temperature for design purposes as a function of coldest air temperature is described in Section 4 0 Transportation Association of Canada 10 33 PERMANENT DEFORMATION Permanent deformation commonly referred to as rutting can be of several types and the cause of each type differs Instability rutting which occurs within the asphalt concrete layer develops when the properties of the compacted asphalt concrete pavement are inadequate to resist the stresses imposed upon it The degree of instability rutting 15 enhanced when high ambient temperatures prevail and when frequent repetitions of heavy axle loads are applied The time of loading i e low vehicle operating speed further accelerates the rate of which instability rutting develops Properties of the aggregate that is incorporated into the paving mixture have the predominant role in controlling instability rutting Physical properties particle shape soundness and toughness and gradation characteristics of the aggregate must be carefully specified to provide adequate shear resistance and to achieve the aggregate skeleton that is required within the compacted pavement to provide for load transfer from tires to the pavement support layers Methodology h
33. es Titre et sous titre TAC User Guide to CAN CGSB 16 3 M90 Asphalt Cements for Road Purposes Auteur s Affiliation s Cece Dawley EBA Engineering Consultants Bert Pulles Nom et adresse de l organisme ex cutant Nom et adresse de l organisme parrain EBA Engineering Consultants 14535 118 Avenue Edmonton Alberta T5L 2M7 Conseil de la recherche et du d veloppement Association des transports du Canada 2323 boulevard Saint Laurent Ottawa Ontario K1G 4K6 Mots cl s R sum La pr sente tude d crit les modalit s de s lection d un bitumineux en fonction de la norme Enrobe de 1990 de l Office des normes g n rales du Canada CGSB intitul e Liants bitumineux pour Dimensionnement les routes CAN CGSB 16 3 M90 Cette norme publi e en 1990 devait servir de norme Choix nationale pour les liants bitumineux Bien que le programme strat gique de recherche routi re ait Recommandation donn lieu plus r cemment une nouvelle norme sur les liants ax e sur le rendement plusieurs Guid administrations canadiennes ont exprim leur intention de continuer utiliser les cat gories de uldage p n tration CGSB Plusieurs versions provisoires d un guide d utilisation de la norme CGSB ont Comptage trafic t pr par es mais aucune n a t publi e L ATC a reconnu que la s lection d
34. hat satisfies the high design pavement temperature requirement at the prevailing operating speed should be identified Conversely for high traffic levels Design Level 3 the hardest penetration grade of those potential candidates would be identified 52 CONSIDERATION OF TRAFFIC AND MINIMUM DESIGN TEMPERATURE Selection criteria relative to minimum design temperature are subjective in nature and should be in accordance with the following guidelines I For low traffic volumes Design Level 1 identify one of the softer penetration grades that are available candidates i For high traffic volumes Design Level 3 identify the hardest penetration grade from available candidates iii For intermediate traffic volumes Design Level 2 identify the most appropriate penetration grade from available candidates using discretion and in consideration of the range of available materials Transportation Association of Canada 21 6 0 OTHER CONSIDERATIONS 6 1 SAFETY FACTORS For Design Service Temperature It has been discussed in previous Sections how the probability of extreme temperature occurrences that exceed average annual mean temperature values can be recognized by adding or subtracting 10 or 26 to from mean temperature values In this manner the temperature variable may be addressed 2 For Initial Age Hardening of Asphalt Cement Asphalt cements are specified in their original tank condition in the CGSB specification
35. is necessary since the two candidate products that most closely satisfy both temperature design requirements are 200 300 Group A and 150 200 Group A Since a 10 C safety factor was designated for design at the low temperature condition it is concluded that 150 200 pen Group A asphalt cement should be specified for the project This selection most adequately satisfies the criteria required to mitigate fatigue distress in a pavement whose thickness is greater than 125 mm Example 3 The project is located on an urban freeway just outside of Toronto Ontario The design operating speed is 100 km h However heavy traffic conditions will mean that traffic will be frequently stopped or slow moving Traffic level 3 conditions prevail ESALs gt 107 tentative pavement design calls for in excess of 200 mm of asphalt concrete over a granular base layer The SHRP database contains the following statistics for Toronto Pearson International Airport Station Code 86158788 Latitude 43 67 Longitude 79 63 m Elevation 173 m Average Low Temperature Tair 25 C Gair 3 2 C Transportation Association of Canada 31 31 C 1 8 C Average High Temperature DMAT The following policies exist in respect to risk for Traffic Level 1 roads Low temperature cracking to be mitigated at the 98 probability level Low pavement temperature safety factor 10 C Permanent deformation rutting
36. isateur du pr sent guide y trouvera une s rie d tapes permettant de choisir en fonction de ces param tres le liant bitumineux le plus appropri Les sections qui suivent d crivent l identification et l analyse de ces param tres en vue de la s lection d un liant bitumineux Le cas particulier des liants bitumineux conventionnels destin s de nouveaux rev tements est galement abord Lechoix d un liant bitumineux en vue d un projet de rev tement devrait tenir compte des conditions existantes et de la d gradation de la chauss e 12 PARAMETRES DE S LECTION D UN LIANT BITUMINEUX Les param tres les plus importants de la s lection d un liant bitumineux pour un projet donn sont les suivants le d bit de la circulation et les contraintes de charges la gamme de temp ratures de service l paisseur et la conception du rev tement les caract ristiques des granulats Le liant bitumineux retenu en vue d un projet repr sente habituellement un compromis entre les mat riaux qui offrent le meilleur rendement compte tenu des modes de d gradation du rev tement qui sont le plus souvent la fissuration par fatigue l orni rage d l instabilit et la fissuration caus e par des contraintes thermiques Certains types de d gradation par exemple la fissuration caus e par des contraintes thermiques sont associ s principalement Association des transports du Canada 4 aux propri t s du liant bitumineux D a
37. m performance of asphalt concrete pavements are low temperature cracking permanent deformation rutting fatigue cracking moisture sensitivity and stripping aging of the asphalt aggregate system durability The role played by the asphalt cement in the paving mixture as it Influences pavement performance is discussed below For certain types of distress such as low temperature cracking the asphalt cement properties are dominant in respect to its occurrence For other types of distress such as permanent deformation the quality of the aggregate in the paving mixture is dominant in preventing its occurrence while the asphalt cement is a secondary or contributing factor Nevertheless the asphalt cement should be selected on the basis of the dominant and or contributing factors that influence pavement performance 3 2 LOW TEMPERATURE CRACKING Low temperature cracking in newly constructed asphalt concrete pavements is predominantly controlled up to 90 percent by the properties of the asphalt cement Other contributory factors include pavement thickness pavement age subgrade characteristics the asphalt mix design and mixture production procedures Low temperature cracking in newly constructed pavement overlays may be influenced by pre existing transverse cracking in the original pavement Several researchers have developed predictive methods for estimation of the cracking temperature of pavements that contain conven
38. mechanisms that cause distress to occur in asphalt concrete pavements and of the role played by the asphalt binder in mitigating their occurrence An explanation is provided of the CGSB specification and of the manner in which the rheological properties of asphalt cements have been used to create a matrix of products for use over the range of climatic conditions which prevail throughout Canada A step by step procedure is presented for selecting the most appropriate asphalt cement grade and group for those anticipated project specific climatic and traffic conditions that the user must identify Examples are provided of how the methodology serves to define an asphalt cement for specific service conditions This Guide is not intended to provide either direction or specifications relative to other components of an all encompassing project of constructing an asphalt concrete pavement including pavement structure design paving mixture design selection and processing construction quality control and quality assurance construction specifications Under certain climatic and service conditions it is possible that asphalt cements specified in the CGSB Standard will not comply with certain requirements that are associated with prevailing traffic and or climatic conditions In such instances consideration may have to be given to selection of alternative products such as polymer modified asphalt The CGSB Standard does
39. r TDY Traffic Days per Year Transportation Association of Canada 24 Step 3 Step 4 The above equation provides an estimate of the number of ESALs in the design lane in one year It is simply necessary to know the proj ect design life and traffic growth factor to determine the anticipated cumulative ESALs in the project design life 2 2 Operating Speed geometric designers and or regulatory agencies usually dictate what the operating speed will be especially with respect to truck traffic These sources should be requested to provide relevant information Determine Low and High Air Temperatures Refer to Chapter 4 and ascertain the four air temperature statistics that are required to determine the relevant design pavement temperatures Sources of air temperature statistics are provided in Chapter 4 A risk analysis should be performed at this stage to establish the level of probability that is acceptable in respect to those selected design temperatures being exceeded during the design period Reference should be made to Chapter 4 in this regard Assign either the mean temperature x or mean temperature plus or minus lo or 20 as being the high and low design air temperatures respectively Calculate Low and High Design Pavement Temperatures 4 11 Design Low Pavement Temperature Using the low air temperature statistics determined in Step 3 calculate the design low pavement temperature Design Low T pavement as follows Design Low
40. rion to focus on rutting and Transportation Association of Canada 7 11 penetration at 25 C which when used in conjunction with viscosity at 60 C would serve as a means for defining temperature susceptibility to avert or minimize low temperature pavement cracking The asphalt cement selection procedure contained in this Guide has been developed on the basis of temperature susceptibility criteria that were utilized to develop Figure 1 of the Standard No further reference to Figure 2 is made herein The term Penetration Index PI was used by researchers to describe the temperature susceptibility parameter as a function of the relationship of penetration and temperature Thus with knowledge of penetration 100 g 5 sec at two temperatures eg 25 C and 10 C the PI of an asphalt could be determined and hence its temperature susceptibility property could be defined It was subsequently demonstrated that nomographical methods use of pen and Viscosity values could be used to approximate very closely the PI determined by the two penetration method for most conventional asphalts Thus the main specified criteria in the Standard were developed on the basis of the pen viscosity 9 temperature susceptibility parameter Transportation Association of Canada 8 3 0 PAVEMENT DISTRESS TYPES AND THEIR MITIGATION 3 1 BACKGROUND The primary types of distress and related factors that may develop and influence long ter
41. rojects should be undertaken in recognition of pre existing pavement conditions and distress features 12 THE CONCEPT FOR SELECTION OF THE ASPHALT CEMENT Factors which are most significant in the selection of the type and grade of asphalt cement for a project include traffic volume and loading service temperature range thickness and design of the pavement structure characteristics of the available aggregates The asphalt cement that is ultimately selected for a project will usually be a compromise between those candidate materials which provide the best performance with respect to primary pavement distress modes and are most commonly considered to be fatigue cracking instability rutting and cracking due to thermal stresses Some types of pavement distress such as cracking due to thermal stresses are predominantly associated with the properties of the asphalt cement Transportation Association of Canada On the other hand other types of pavement distress such as instability rutting are The concept associated with use of this Guide is to enable the most appropriate asphalt cement as provided for within CAN CGSB 16 3 M90 to be selected in consideration of the relative significance of the factors that influence asphalt concrete pavement performance under prevailing climatic traffic and other service conditions 13 CONTENTS OF THE USER GUIDE In following Sections of this Guide a brief description is provided of the
42. rses gently rolling terrain and has a design operating speed of 100 km h Traffic Level No 1 conditions prevail ESALs lt 10 The total design pavement thickness is 100 mm The SHRP database contains the following statistics for a nearby weather station which is in close proximity to the project Latitude 49 3 Longitude 101 0 Elevation 442 m Average Low Temperature T 39 C 2 9 C Average High Temperature DMAT 32 C 2 4 C OpMAT Following policies exist in respect to risk in pavement design and performance for Traffic Level 1 roads Low temperature cracking to be mitigated at the 98 probability level Low pavement temperature safety factor 10 C applies Permanent deformation rutting tolerable at the 50 probability level Transportation Association of Canada 29 At the completion of Steps 1 to 5 on the accompanying flow chart it is apparent that to satisfy low service temperature conditions a 300 400 Group A or a grade with a higher penetration should be used To satisfy high service temperature requirements a 200 300 Group A is required or a 150 200 Group B or harder A compromise solution is necessary since the candidate products for low temperature are not the same as for high temperature In this instance since permanent deformation is not critical 50 probability level required for rutting design a 300 400 Group A would be most suitable for cold temperatur
43. s e la conception du m lange routier la s lection et le traitement des granulats l assurance de la qualit et le contr le de la qualit les normes de construction Compte tenu des conditions climatiques et de service il est possible que des liants bitumineux d crits dans la norme CGSB ne r pondent pas certaines exigences li es des conditions climatiques ou routi res existantes Le cas ch ant il faudra peut tre choisir d autres produits comme un bitume modifi par des polym res La norme CGSB ne comporte aucune sp cification relative des liants am lior s et la s lection de tels produits d passe le cadre du pr sent guide Association des transports du Canada 5 L ATC a publi un rapport intitul Characteristics Performance and Selection of Paving Asphalts Ce rapport qui contient beaucoup de d tails qui ont appuy la pr paration du pr sent guide cite une bonne partie de la recherche qui a t men e au Canada et ailleurs et il aborde des d marches entreprises dans le cadre du programme strat gique de recherche routi re SHRP et de son homologue canadien C SHRP Pour en savoir davantage l utili sateur du guide pourra consulter ce rapport de l ATC Association des transports du Canada 6 2 0 CAN CGSB 16 3 M90 The Guide user should be thoroughly familiar with the contents of the CGSB Standard for Asphalt Cements for Road Purposes Six penetration grades are provided for
44. that the selection of asphalt paving cements on a project specific basis using the CGSB standard alone is not a straightforward procedure Therefore TAC has sponsored the development of this User Guide to the CGSB specification based on the best information currently available on 1 Canadian climatic conditions 2 sources and characteristics of asphalts used in Canada 3 Canadian pavement performance data 4 current provincial asphalt specifications and test procedures 5 the likely impacts of the results of the Strategic Highway Research Program asphalt research results and 6 use of premium and polymer modified asphalts The User Guide is intended to be used as a supplement to the CGSB standard and contains step by step procedures with worked examples for the selection of asphalts for any paving project in Canada based on climatic conditions and anticipated traffic levels A detailed final report is also available which contains full documentation of the research that led to the development of the User Guide To assist with the pavement selection process a printout of minimum and maximum temperature data from Canadian weather stations has been extracted from the SHRPBIND weather database and is also available separately from TAC No of Pages No of Figures Supplementary Information FICHE DE RAPPORT DE L ATC DIRR n Rapport n Date du rapport JAN 96 Gestionnaire du projet Christopher Hedg
45. tional asphalt cements whose rheological viscosity penetration properties are known Methodology selected for incorporation into this Guide was developed by E E Readshaw 1972 and it along with that of others is discussed in the TAC Report Transportation Association of Canada 9 Readshaw s procedure is based on a critical asphalt stiffness of 2 x 108 N m at two hours loading time That is the pavement cracking temperature is that temperature which exists for two hours at which time the asphalt attains a stiffness value of 2 x 108 N m Cracking temperatures of pavements containing CGSB Groups A B and C asphalt cements of the six previously defined penetration grades have been computed using Readshaw s methodology To mitigate low temperature cracking an asphalt cement should be selected that has a stiffness value that is less than 2 x 10 N m at two hours loading time at the low design pavement temperature The design pavement temperature selection procedure is explained in Section 4 0 Figure 1 may be used to predict the cracking temperature of a pavement containing asphalt cement whose original penetration 100 g 5 sec 25 C and viscosity Pa s 60 C are specified or known Figure 2 may be used for this purpose when the original penetration 100 g 5 sec at 25 C is known or specified and at least one additional penetration value 100 g 5 sec at a different temperature eg 10 C is also specified or known with which to det
46. tistics may be sourced as referenced on Section 4 2 The user at his discretion may accept increased risk by deleting the 20 Value from Equation 1 i e 50 percent risk factor or by substituting 10 84 percent risk factor The TAC Report may be referenced for detailed information relative to the development of Equation 1 above The Guide user is reminded of the need for validating the value of T available in the reference source for any project specific application Transportation Association of Canada 17 Note The Guide user is cautioned to read and to understand fully the contents of Chapter 6 1 Safety Factors and the requirement contained therein for refining design low pavement temperature values derived from Equation 1 in accordance with guidelines contained in Chapter 6 1 4 4 SELECTION OF THE DESIGN HIGH PAVEMENT TEMPERATURE Protocols that were developed by SHRP have been adopted for determining the design high pavement temperature from air temperature data that is provided in the SHRPBIND program In the methodology that is defined below for determining the design high pavement temperature SHRP has defined the critical location in the pavement structure as being that point located 20 mm below the surface of the pavement The user may assign the risk of the design high pavement temperature being exceeded in terms of probability by defining in Equation 2 below as follows Probability 96 Value of T 84
47. urage les activit s de R D et diffuse l information sur le sec teur les transports qu elle m me et d autres organismes r unissent Le r le du Conseil de la recherche et du d veloppement de l ATC est de contribuer l essor du secteur canadien des transports en favorisant la mise en oeuvre de projets de recherche innovateurs efficients et efficaces ainsi que le transfert de la technologie issue de ces derniers Le pr sent projet a t ex cut la faveur de programme de recherche col laborative du Conseil programme financ par les minist res f d ral provinciaux et territoriaux des Transports The views opinions and conclusions expressed or implied in this report are those of the authors and do not necessarily reflect the postion or policies of the Transportation Association of Canada The material presented in the text was carefully research and presented However no warranty expressed or implied 15 made on the accuracy of the contents or their extraction from reference to publications nor shall the fact of distribution constitute responsibility by TAC or any research or contributors for omissions errors or possible misrepresentations that may result from use or interpretation of the material contained herein Transportation Association of Canada 1996 2323 St Laurent Blvd Ottawa Canada K1G 4K6 Tel 613 736 1350 Fax 613 736 1395 ISBN 1 55187 096 7 TAC REPORT DOCUMENTATION FORM Report No
48. utres types de d gradation par exemple l orni rage d l instabilit sont surtout li s aux propri t s du granulat les propri t s du hant bitumineux tant consid r es comme un facteur contributif Le pr sent guide cherche faciliter la s lection du liant bitumineux le plus appropri dans le cadre de la norme CAN CGSB 16 3 M90 compte tenu de l importance relative des param tres qui influencent le rendement d une chauss e de b ton bitumineux conditions climatiques routi res et autres 13 CONTENU DU GUIDE Les sections du guide d crivent bri vement les m canismes de la d gradation des chauss es de b ton bitumineux ainsi que le r le du liant bitumineux dans la r duction de cette d gradation On y trouve une description de la norme CGSB et des propri t s rh ologiques des liants bitumineux qui ont permis d offrir un choix de produits adapt s aux conditions climatiques existantes dans l ensemble du Canada Le guide expose m thodiquement les tapes de la s lection du liant bitumineux le plus appropri en fonction des conditions climatiques et routi res particuli res identifi es par l utilisateur Des exemples de hants bitumineux sont pr sent s pour des conditions de service particuli res Le pr sent guide ne cherche ni orienter ni normaliser les autres aspects d un projet global de construction d une chauss e de b ton bitumineux par exemple a conception de la structure de la chaus
49. vided of methodology that has been used in this Guide to enable design pavement temperatures to be predicted for both the hot and cold service temperature conditions using the four temperature statistics defined above An understanding of statistics principles that are associated with normal distribution theory is necessary to appreciate how SHRP has accommodated the issue of risk i e probability A normal distribution curve is shown in Figure 9 The area under a normal distribution curve represents the total number of records in a dataset The area under a portion of the curve represents the number of pieces of data and hence the percent of the dataset In the illustration in Figure 9 the 7 day average maximum pavement temperature situation is represented For each case of x lo 20 or 30 the percentage of occurrences and also the probability of temperatures occurring outside of those limits may be determined In the high design temperature case one is only concerned with probability that a temperature occurrence may exceed i e fall to the right of a definable probability level Thus when the mean temperature X is considered there exists 50 percent probability that an annual temperature occurrence Transportation ssociation of Canada 15 will exceed x Similarly for 10 and x 26 there exists 84 percent and 98 percent probabilities respectively that annual temperature occurrences will not exceed those limits The s
50. within the Standard 60 70 150 200 80 100 200 300 120 150 300 400 In addition three Groups of asphalt cements are defined in accordance with their temperature susceptibility properties Temperature susceptibility is defined as the change in consistency viscosity or penetration that an asphalt cement undergoes for a given change in temperature Thus the temperature susceptibility properties by Group are Group A asphalt cements that have a high viscosity at 60 C or 135 C for a given penetration at 25 C low temperature susceptibility Group B asphalt cements that have a medium viscosity at 60 C or 135 C for a given penetration at 25 C medium temperature susceptibility Group C asphalt cements that have a low viscosity at 60 C or 135 C for a given penetration at 25 high temperature susceptibility A matrix of eighteen candidate asphalt cements exists as a function of penetration grade and temperature susceptibility Group Requirements and specifications for these asphalt cements are outlined in Table 1 of the Standard Table 1 of the Standard contains reference to Figure 1 viscosity at 60 C or Figure 2 viscosity at 135 C as the means by which viscosity properties for Group A B and C asphalt cements are specified The Committee that developed this Standard agreed that the asphalt cement specification should be based on i viscosity at 60 C which would serve as a performance crite
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