Understanding the MSCR Test and its Use in the PG Asphalt Binder Specification. R. Michael Anderson, Asphalt Institute 31 August 2011

Transcription

1 Understanding the MSCR Test and its Use in the PG Asphalt Binder Specification R. Michael Anderson, Asphalt Institute 31 August 2011

2 MSCR Webinar Webinar Objectives Understand why the MSCR test is needed to characterize the performance of asphalt binders Understand how the test is performed Understand how and why the MSCR test values J nr, %Recovery, and Stress Sensitivity are used Understand how the proposed specification works

3 Acknowledgments DTFH61-08-H Cooperative Agreement between the FHWA and the Asphalt Institute John Bukowski, AOTR John A. D Angelo Asphalt Binder ETG Member Companies of the Asphalt Institute Technical Advisory Committee

4 How Asphalt Behaves Behavior is affected by : Temperature Time of Loading Age of pavement or service life

5 60C 1 hour 25C 1 hour 10 hours

6 Pavement Behavior High Temperature Permanent Deformation Mixture is Plastic wheel path rutting shoving at intersections Depends on asphalt cement (some) mineral aggregate (some) volumetric proportioning (some)

7

8 Testing of Asphalt Cements Characteristics of Asphalt Cements Consistency term used to describe the viscosity or degree of fluidity of asphalt at any particular temperature varies with temperature necessary to define an equivalent temperature or an equivalent consistency when comparing temperatureconsistency characteristics of asphalt cements

9 Viscosity Absolute Viscosity ASTM D2171; AASHTO T202 Conducted at 60 C (140 F) Uses partial vacuum to induce flow through capillary tube Kinematic Viscosity ASTM D2170; AASHTO T201 Conducted at 135 C (275 F) Uses gravity to induce flow through capillary tube

10 Viscosity

11 Asphalt Cement Viscosity Graded Asphalt 60 C (140 F) selected to simulate in-service temperature of asphalt pavements 135 C (275 F) selected to simulate mixing and laydown temperature for HMA

12 Problems with Previous Systems Penetration empirical measure of viscous and elastic effects Viscosity viscous effects only No Low Temperature Properties Measured Problems Characterizing Modified Asphalt Binders Specification proliferation Long Term Aging not Considered

13 Apparent Viscosity, P Problems with Previous Systems 32,000 30,000 28,000 26,000 24,000 22,000 PBA-6A 20, Shear Rate, s -1

14 PG System Concept the values of the specification criteria that warrant against distress are independent of temperature, but the values must be obtained at different temperatures according to climate. This implies test measurements at temperatures and loading rates consistent with conditions existing in the pavement.

15 Superpave Binder Testing Performance-Based Physical Properties Measured by Rotational Viscometer (RV) (high temps) Dynamic Shear Rheometer (DSR) (high, intermediate temps) Bending Beam Rheometer (BBR) (low temps) Direct Tension Tester (DTT) (low temps) Pavement Temperature ( o C)

16 Performance Grades

17

18 Performance-Related Requirements Shearing resistance to resist traffic loads Upper specification temperature G*/sin 1.00 kpa Tank G*/sin 2.20 kpa RTFOT residue

19 Grade-Bumping: Used to Increase Rutting Resistance (AASHTO M 323)

20 The SHRP PG Binder Tests Dynamic Shear Rheometer (DSR), AASHTO T315 for determining the modulus (stiffness) of asphalt binders at intermediate and upper pavement temperatures.

21 Dynamic Shear Rheometer Test procedure results in complex modulus and phase angle Specification test is conducted at 10 rad/s Temperature range from 3 C to 88 C Parallel plate geometry Valid for linear viscoelastic materials Materials with moduli that are independent of applied stress or strain Particles must be < 250 microns

22 DSR Test Fundamentals Asphalt binder is placed between two parallel plates Upper plate it is rotated with respect to lower plate Cyclical rotation A-B-A-C-A-B-A-C-A, etc. Maximum stress and strain in each direction are measured

23 Elastic: = 0 deg Viscous: = 90 deg Applied Shear Stress max max time Resulting Shear Strain max max time time lag converts to

24 Viscoelastic: 0 < < 90 Applied Shear Stress max time G* = max max Resulting Shear Strain max time = 360tf 2p

25 Viscous Part (G ) Viscous Part (G ) Asphalt A G* Asphalt B G* Elastic Part (G ) sin = Elastic Part (G ) Viscous Part (G ) G*

26 Shortcomings of G*/sin G*/sin as a High Temperature Parameter Properties determined in Linear Viscoelastic (LVE) region No damage behavior Rutting is a non-linear failure Polymer-modified systems engaged in non-linear region Characterizes stiffness Related to rutting

27 Sin Effect of Phase Angle Phase Angle, degrees

28 ALF Study - 7 Asphalt Binders AZ PG CRM Air Blown Control SBS TX TBCR TP PG PG Fibers SBS Air Blown SBS TP

29 G*/sin d 64C Relationship between G*/ sinδ and ALF rutting y = x R 2 = Existing SHRP specification has poor relationship to rutting for modified systems rutting inches

30 NCHRP 9-10 NCHRP 9-10 Asphalt Binders PG SBS-radial PG Polyethylene-stabilized PG Steam Distilled PG SBR-low molecular weight PG Ethylene Terpolymer PG Oxidized PG SBS-linear PG SB Di-block PG Oxidized

31 NCHRP 9-10 Binders Excerpt from NCHRP Report 459, Characterization of Modified Asphalt Binders in Superpave Mix Design

32 Kentucky Study October 2001

33 Kentucky Study Kentucky PG Study (1996) Evaluate PG asphalt binders produced by different methods SBS (2) SBR Gel Select Crude I-64 near Winchester Duplicate 1-mile test sections using each asphalt binder Asphalt binder and mixture testing

34 Effect of Binder G*/sin on Mixture Permanent Shear Strain microstrain y = e -0.09x R 2 = RTFO G*/sin, 70C

35 PG Grading Alone Does Not Always Predict Performance Study of the two mixes with the same aggregate structure, but different binders. PG modified, no rutting PG unmodified, 15mm rut

36 AASHTO M320 and Polymer- Modified Binders Why doesn t AASHTO M320 properly characterize polymer-modified binders? Current spec, G* and δ are measured in the linear viscoelastic range. For neat asphalts, flow is linear and not sensitive to the stress level of the test. For polymer-modified binders, the response is not linear and sensitive to the stress level of the test. The polymer chains can be rearranged substantially as the stress increases.

37 AASHTO M320 and Polymer- Modified Binders What happened as a result of the inability to properly characterize polymer-modified binders? Most states began requiring additional tests to the ones required in AASHTO M320 These mostly empirical tests are commonly referred to as PG Plus tests These tests are not standard across the states difficult for suppliers Even some of the tests that are the most common, e.g. Elastic Recovery, are not run the same way from state to state

38 States with a PG Plus Specification * * * PG Plus Spec No PG Plus Spec

39 NCHRP 9-10: High Temperature Testing Repeated Shear Creep Analogous to mixture test (RSCH) Performed in DSR Controlled shear stress (i.e., 25 Pa or 300 Pa) 100 cycles 1-second load, 9-second rest per cycle High test temperature (HT-?) Response: permanent shear strain ( p ) or strain slope

40 Perm. Shear Strain, % Repeated Shear Creep Instantaneous shear strain Recoverable shear strain Permanent shear strain Time, seconds

41 NCHRP 9-10 Excerpt from NCHRP Report 459, Characterization of Modified Asphalt Binders in Superpave Mix Design

42 NCHRP 9-10 J nr = /0.3 kpa = 0.35 kpa -1 Rec = ( )/0.125 = 16% J nr = /0.3 kpa = 0.25 kpa -1 Rec = ( )/0.125 = 40% γ peak γ nr J nr = /0.3 kpa = 0.15 kpa -1 Rec = ( )/0.125 = 64% Excerpt from NCHRP Report 459, Characterization of Modified Asphalt Binders in Superpave Mix Design

43 Perm. Shear Strain, % Repeated Shear Creep NCHRP 9-10: PG 82 Binders Repeated Shear Creep (70C, 300Pa) Time, seconds Ox PE-s SBS-r

44 NCHRP 9-10: Relationship of Binder RCR to Mixture Rutting Excerpt from NCHRP Report 459, Characterization of Modified Asphalt Binders in Superpave Mix Design

45 Problem Statement Provide Users a High Temperature Binder Spec Blind to Modification Provide Users with alternatives to the empirical Superpave Plus tests Elastic Recovery Ductility/ Force Ductility Toughness and Tenacity Approach: Develop AASHTO/ASTM Standard Practice for Superpave Plus Specifications DSR Multiple Stress Creep Recovery

46 High Temperature Specification Parameter Related to Rutting Any new specification must be blind to modification. A new specification must identify the rutting potential of all binder types under multiple conditions. Binders are stress sensitive and different mix tests apply different stress conditions.

47 Multiple Stress Creep Recovery Test Performed on RTFO-aged Binder Test Temperature Environmental Temperature Not Grade-Bumped 10 cycles per stress level 1-second loading at specified shear stress 0.1 kpa 3.2 kpa 9-second rest period

48 Standard Test Procedure developed for AASHTO

49 Multiple Stress Creep Recovery The test method is detailed in AASHTO TP70 The test uses the same Dynamic Shear Rheometer (DSR) as required in M320 Only minor software changes are need to run the MSCR test The test uses the creep and recovery method to measure the percent recovery and nonrecoverable creep compliance (J nr )

50 Multiple Stress Creep Recovery Definitions: Creep and recovery a standard test protocol whereby a specimen is subjected to a constant load for a fixed time period and then allowed to relax (recover) at a zero load for a fixed time period Percent Recovery A measure of how much the sample returns to its previous shape after being repeatedly stretched and then relaxed Non-Recoverable Creep Compliance (J nr ) a measure of the amount of residual strain left in the specimen after repeated creep and recovery, relative to the amount of stress applied

51 Multiple Stress Creep Recovery Test Calculate Non-recoverable Creep Compliance (J nr ) Non-recoverable shear strain divided by applied shear stress J = compliance nr = non-recoverable Calculate Recovery for each Cycle, Stress Difference between strain at end of recovery period and peak strain after creep loading

52 Perm. Shear Strain, % MSCR Instantaneous shear strain Recoverable shear strain Non-recoverable (permanent) shear strain Time, seconds

53 Strain, % MSCR Non-Recoverable Compliance (J nr ) 80 J nr = Unrecovered Shear Strain Applied Shear Stress Cycle 1 Unrecovered (permanent) strain Time, seconds Cycle 2 Unrecovered (permanent) strain Cycle 3 Unrecovered (permanent) strain

54 Strain MSCR Non-Recoverable Compliance (J nr ) J nr = kpa Shear Stress Unrecovered Shear Strain Applied Shear Stress J nr = kpa = 1.97 kpa Cycle 1 Unrecovered (permanent) strain Time, seconds

55 Normalized strain [%] Normalized Creep and Recovery Cycles for a Neat PG 0.1 kpa and 70ºC Time [s]

56 Normalized strain [%] Normalized Creep and Recovery Cycles for a Neat PG 3.2 kpa and 70ºC Time [s]

57 Normalized strain% Normalized Creep and Recovery Cycles for a PMA PG 0.1 kpa and 58ºC Time s

58 Normalized strain % Normalized Creep and Recovery Cycles for a PMA PG 3.2 kpa and 58ºC time s

59 MSCR Calculations: J nr Meas. Pts. Time Shear Stress Strain [s] [Pa] [%] E = initial strain r = strain at the end of recovery 10 = total strain at 10 seconds τ = applied shear stress, kpa 10 = ( r 0 )/100 J nr = 10 τ

60 MSCR Calculations: J nr Meas. Pts. Time Shear Stress Strain [s] [Pa] [%] E = initial strain = 0 for 1 st cycle r = strain at the end of recovery 10 = total strain at 10 seconds τ = applied shear stress, kpa 10 = ( r 0 )/100 = ( )/ = τ = 100/1000 = 0.1 kpa J nr = = τ J nr = kpa

61 MSCR Calculations Stress 100 Cycle 0 c 1 r 10 Recovery Jnr, kpa Average

62 MSCR Calculations: Jnr Stress 100 Cycle 0 c 1 r 10 Recovery Jnr, kpa Average J nr = non-recoverable strain at the end of the cycle divided by applied stress

63 MSCR Calculations: Jnr Stress 100 Cycle 0 c 1 r 10 Recovery Jnr, kpa Average J nr = 10 (not expressed as a %) Stress (expressed in kpa)

64 MSCR Calculations: Jnr Stress 100 Cycle 0 c 1 r 10 Recovery Jnr, kpa Average J nr = % 100% 100 Pa 1000 Pa/kPa =

65 MSCR Calculations: Recovery Meas. Pts. Time Shear Stress Strain [s] [Pa] [%] E = initial strain c = strain at the end of creep 1 = total strain at 1 second r = strain at the end of recovery 10 = total strain at 10 seconds 1 = c 0 10 = r Recovery = 100 x

66 MSCR Calculations: Recovery Meas. Pts. Time Shear Stress Strain [s] [Pa] [%] E = initial strain = 0 for 1 st cycle c = strain at the end of creep r = strain at the end of recovery 1 = c 0 = = = r 0 = = Recovery = 100 x Recovery = 60.7%

67 MSCR Calculations: Recovery Stress 100 Cycle 0 c 1 r 10 Recovery Jnr, kpa Average Recovery = ratio of recoverable strain to total strain

68 MSCR Calculations: Recovery Stress 100 Cycle 0 c 1 r 10 Recovery Jnr, kpa Average Recovery = x 100%

69 MSCR Calculations: Recovery Stress 100 Cycle 0 c 1 r 10 Recovery Jnr, kpa Average Recovery = x 100% = 48.8%

70 Stress Sensitivity Parameter J nr, diff = (J nr, 3.2kPa - J nr, 0.1kPa ) J nr, 0.1kPa x % For polymer-modified binders, the strain response is not linear and sensitive to the stress level of the test. The polymer chains can be rearranged substantially as the stress increases. This parameter is a check on the phenomenon.

71 MSCR Calculations Stress 100 Cycle 0 c 1 r 10 Recovery Jnr, kpa Average Stress 3,200 Cycle 0 c 1 r 10 Recovery Jnr, kpa Average

72 MSCR Calculations Stress 100 Cycle 0 c 1 r 10 Recovery Jnr, kpa Average Stress 3,200 Cycle 0 c 1 r 10 Recovery Jnr, kpa Average Stress Sensitivity = J nr,3.2 J nr,0.1 J nr,0.1 Stress Sensitivity = Stress Sensitivity = 0.17

73 MSCR and Rutting What is the relationship of J nr to Rutting? The relationship was determined with many field and lab studies using many modified and neat binders. During Specification development many stress levels where evaluated in the test.

74 G*/sin d 64C Relationship between G*/ sinδ and ALF rutting y = x R 2 = Existing SHRP specification has poor relationship to rutting for modified systems rutting inches

75 Jnr Relationship between J nr and ALF Rutting 25.6kPa Jnr = (4.74*Rut Depth) R 2 = MSCR can adjust for field conditions and has excellent relations to performance ALF Rutting, in

76 Effect of Binder G*/sin on Mixture Permanent Shear Strain microstrain y = e -0.09x R 2 = RTFO G*/sin, 70C

77 microstrain Effect of Binder J nr on Mixture Permanent Shear Strain y = e 0.58x R² = C (kpa -1 )

78 J 3.2kPa (1/kPa) Mississippi I55: 6-Year Rutting Compared to J nr 3.2 kpa 4 3 y = 0.29x R 2 = Rut Depth, mm

79 Hamburg Rut Testing: MnROAD Mixes Tested at Multiple Temperatures Jnr 12.8 kpa PG PG J nr kpa PG y = x R 2 = rut mm

80 High Temperature Binder Criteria Linear binder tests will not correlate with high temperature mixture failure tests unless the binder is a viscous fluid at those temperatures To accurately address mix failure, non-linear binder properties have to be evaluated Creep & Recovery testing of the binder at different stress levels is needed to describe binder properties in the non-linear range

81 Effect of J nr on Rutting Reducing J nr by half typically reduced rutting by half This effect is seen on ALF sections and Hamburg Rut Testing But most importantly this is seen on the Mississippi I-55 sections.

82 Determination of Specification Criteria The existing binder specification works very well for neat binders. The grading for neat binders should not change. Establish new J nr criteria based on response of neat binders at their continuous grade temp. Evaluate the binders near the end of their linear range. Most neat binders remain linear up to 3.2 kpa stress.

83 Jnr Neat PG58-28 at Multiple Temperatures C 64C 70C Neat binders are typically linear up to 3.2 kpa or higher Stress Pa

84 Evaluation of Straight-Run Binders Sample ID Name Grade true grade Temp Jnr 3.2kPa ALF 6727 Control BBRS3 straight MN county rd 112 neat Valero MN county rd 112 neat Citgo MN county rd 112 AshlandM Minn Road straight Miss I-55 CSL Shandong straight BBRS3 straight BBRS3 straight MD project straight average 4.13

85 MSCR Polymer modified binders have shown significant sensitivity to the applied stress. The existing SHRP binder specification does not identify this issue.

86 Jnr SBS PG SBS C 64C 70C 76C 72C calc Compliance values increase with temperature and stress. The rate of increase with stress increases with increased temperature Stress Pa

87 Jnr Variations in Temp sensitivity 3.2kPa SBS Elvaloy PG y = 4E-17x R 2 = SBS-El PG Neat binders have similar temp. sensitivity modified binder do not. y = 8E-19x R 2 = 1 y = 2E-22x R 2 = y = 6E-27x R 2 = y = 1E-19x R 2 = Temp C

88 Effect of Temp and Stress on J nr In neat binders a grade bump by temperature will more than double the J nr value. Some neat binders will maintain their compliance value well beyond the 3.2 kpa stress. M320 Grade bumping (increasing PG grade temperature) have forced suppliers to use very soft base binders and high degree of polymer modification to meet wide temperature ranges and the 2.2 kpa for the RTFOT. This has made some polymers very stress sensitive.

89 Grade Bumping Recommendation All testing should be done at the environmental grade temperature one shift factor does not work for all polymer-modified asphalt binders. The standard grade should be based on the J nr value of existing neat binders (4.0 kpa -1 ). For high traffic, the J nr value should be reduced by half at the grade temperature to 2.0 kpa -1 For very high or standing traffic, the J nr value should be reduced by half again to 1.0 kpa -1 For extreme traffic (high volume, slow or standing), the J nr value should be reduced by half again to 0.5 kpa -1

90 Purpose of the Stress Sensitivity Requirement Stress sensitivity requirement limits the change in compliance J nr with stress level to less than on full grade change. The stress sensitivity requirement is an additional safety factor if the pavement experiences higher than expected temperatures and or higher loading.

91 Stress Sensitivity of the ALF Binders C AB 64C SBS LG J nr kpa control 64C Elvaloy 64C TBCR 64C Stress kpa

92 Effect of Temperature and Stress on J nr Some binders are very sensitive to stress showing large increases in compliance with increased stress level. These same binders are very often more sensitive to temperature changes also showing large increases in compliance with increased temperature. The 3.2 kpa stress level in the MP 19 spec was a compromise where there was good correlation to field performance, but lab testing at higher temperatures and accelerated loading at higher stress levels correlated better to rutting.

93 New High Temperature Binder Specification AASHTO MP19 The new specification is based on the nonrecoverable compliance (J nr ) of the binder All testing should be done at the pavement environmental grade temp to reflect response at actual operating temperatures The test should be run at two stress levels 0.1 and 3.2 kpa for ten cycles at each level. Low temp BBR and DTT remain unchanged

94 AASHTO MP19 Original DSR G*/sinδ Min RTFOT 64 Standard MSCR3.2 < Heavy MSCR 3.2< Very heavy MSCR3.2 <1.0 [(MSCR3.2 MSCR 0.1)/ MSCR 0.1] < PAV S grade DSR G*sinδ Max 5000 H & V grade DSR G*sinδ Max Low temp BBR and DTT remain unchanged

95 AASHTO MP19 Grades Based on Climatic Temperature High and Low Pavement Temperature Traffic Designation S Standard H Heavy V Very Heavy E Extreme

96 New PG Grading System (MSCR) Environmental grade plus traffic level designation; i.e. PG 64-22E Four traffic levels S = Standard: H = Heavy: < 10 million ESALs and standard traffic loading million ESALs or slow moving traffic loading V = Very Heavy: > 30 million ESALs or standing traffic loading E = Extreme: > 30 million ESALs and standing traffic loading

97 New High Temperature Specification PG 64 (Standard, Heavy, Very Heavy, Extreme) based on traffic PG 64-xxS J nr =< 4.0 PG 64-xxH J nr =< 2.0 PG 64-xxV J nr =< 1.0 PG 64-xxE J nr =< 0.5

98 AASHTO MP19 PG 64-22V asphalt binder What do I need to test? What are the temperatures and criteria?

99 PG 64-22V Asphalt Binder Original (Unaged) Binder COC Flash Point Must be 230 C Rotational 135 C Must be 3 Pa-s DSR (AASHTO T315) G*/sin must be C

100 PG 64-22V Asphalt Binder RTFO Aged Binder RTFO Mass Change Must be 1.00% DSR (AASHTO TP70) J nr must be C Stress Sensitivity must be 0.75

101 PG 64-22V Asphalt Binder PAV Aged Binder DSR (AASHTO T315) G*sin must be C BBR (AASHTO T313) S(60) must be C m(60) must be -12 C

102 AASHTO MP19 Grades Within same climatic grade all test temperatures stay same PG 64-22_ Original 64 C RTFO 64 C PAV 25 C -12 C Criteria changes depending on traffic designation

103 Grade Bumping with MP19 Without temperature bumping how is the binder grade adjusted for traffic? Can the existing LTPPBind software still be used for grade bumping?

104 LTPPBind 3.1 can still be used for binder selection. The unadjusted grade is the New S grade. PG 58S

105 LTPPBind 3.1 can still be used for binder selection. As the temperature is adjusted for speed or traffic instead of bumping with temp bump to H, V, or E. In this case PG58V

106 MSCR: What is % Recovery? MSCR J nr addresses the high temperature rutting for both neat and modified binders, but many highway agencies require polymers for cracking and durability. The MSCR % Recovery measurement can identify and quantify how the polymer is working in the binder.

107 % recovery MSCR %Recovery: Validate Polymer Modification High elasticity y = x Poor elasticity Jnr kpa

108 % recovery MSCR %Recovery: Validate Polymer Modification Minimum value for J nr.125 to.25 grade Minimum value for J nr.5 to 1 grade Minimum value for J nr 1 to 2 grade y = x Jnr 1/kPa

109 MSCR %Recovery: Table of Minimum Values Minimum % Recovery for Measured J nr values J 3.2 kpa Minimum % Recovery % % % %

110 Recovery, % Validate Polymer Modification Recovery = 29.37*(Jnr ) 60 High Elasticity Low Elasticity Jnr, kpa -1

111 64C, % Validate Polymer Modification PG Binders: MSCR y = 29.82x R² = 0.54 Recovery = 29.37*J nr C, kpa -1

112 Blending of Binders and Polymers: MSCR Study PG Base asphalt 4 % SBS polymer Radial Linear 0.5% PPA 2 blending temperatures

113 % strain Polymer Network Affects Response binders same base asphalt all with 4% SBS polymer. 2 with.5% PPA all have different properties LC P4 70C LOP 4P 70C LC 4 70C LOP 4 70C time s

114 Cycles to Failure, (N f ) Fatigue Evaluation 1.00E+07 ASTM point Flexural Fatigue Cycles*Stiffness Analysis 20 0 C Test Temperature 1.00E+06 ER = 68% MSCR Recovery = 30.8% DLSI-4 PG 64-22V DLSI-2 PG 64-22V 1.00E E+04 ER = 65% MSCR Recovery = 24.7% y = 8.69E+20x -5.60E+00 R² = 9.33E-01 y = 3.44E+25x -7.27E+00 R² = 9.53E E ,000 1,100 1,200 Microstrain

115 Implementation Activities User-Producer Groups Task Force participation Coordination of round-robin testing Conducting testing for individual user agencies

116 Implementation Assistance Educational FHWA Technical Brief FHWA HIF Asphalt Institute Guidance Document, Implementation of the Multiple Stress Creep Recovery Test and Specification Guidance Document, Using the MSCR Test with the AASHTO M320 Specification Engineering/MSCR Information

117 Implementation Telephone survey in 2010 and since indicate that there are barriers to state MSCR implementation Inadequate DSR equipment/software Lack of resources to perform transitional tests Lack of guidance from suppliers and other states Uncertainty about effect on binder supply and modification

118 Survey Results - Barriers 9 of 14 states said biggest barrier was concerns over correlation between existing PG Plus and new MSCR criteria Comment: Satisfied with the PG polymer modified binder performance. There is a perception that moving to MSCR test may result in lower polymer loading and reduction in binder performance.

119 Survey Results - Training 11 of 14 states said they could use some type of training 8 requested classroom training 9 requested laboratory training Comments: More important than training is keeping abreast of progress around the country Internet based training would be preferred since travel is restricted

120 Implementation Recognize that the refineries that serve your state may also serve bordering states. This may be a good reason to work with other states to implement regionally Note that every Performance Grade may not equate to a distinct MSCR grade - for example, the current polymer loading in both a PG and PG may be high enough that both grade to a PG E

121 Implementation Some agencies may be reluctant to implement MSCR fully, since the names by which they refer to binder types will necessarily change. PG H instead of PG 70-22, for a possible example AI s Guidance on the Use of the MSCR Test with the AASHTO M320 Specification.

122 High PG Map (98%)

123 Recommended Testing Temperature (M320 Grade) TABLE 1: Recommended MSCR Testing Temperature (based on M320 Grade) MSCR Test Temperature 1, C Grade 2 States PG X PG X PG X PG X PG X PG X 4 X 4 PG X PG X PG X PG X 5 X 5 PG X 4 X 4 PG X PG X PG X PG X PG X 5 X 5 PG X 4 X 4 PG X PG X PG X 5 X 5 PG X 4 X 4 PG X 6 X 6 PG X PG X 5 X 5 1 All MSCR testing is performed on the asphalt binder after RTFO-aging. 2 AASHTO M320 Table 1. Premium grades (defined as those grades where the temperature differential is 92 degrees or greater) are shown in red. 3 Number of states listing the grade in the Asphalt Institute binder specification database ( 4 Test at either 52 C or 58 C depending on the climate of the project. Users can test at both temperatures if desired. 5 Test at either 58 C or 64 C depending on the climate of the project. Users can test at both temperatures if desired. 6 Test at either 64 C or 70 C depending on the climate of the project. Users can test at both temperatures if desired.

124 Implementation Importantly, AI recommends that if the MSCR test is implemented to evaluate the delayed elastic response of binders, then other PG Plus tests with a similar purpose - such as Elastic Recovery, Force Ductility, and Toughness and Tenacity tests - should be eliminated. If you are conducting side-by-side testing for a while as a precaution, keep in mind that these types of tests give much more simplified results with a much higher degree of error than the MSCR, so agencies should not expect a strong correlation between them and MSCR results.

125 Why MSCR? Why Use the MSCR Test and Spec? Non-recoverable creep compliance, J nr, is better correlated with pavement rutting than G*/sin δ The high temperature parameter is truer to the intent of the PG specification, that it be blind to method of modification

126 Why MSCR? Why Use the MSCR Test and Spec? MSCR Recovery can be used to identify elastomeric modification, thereby eliminating the need for many PG-Plus tests like Elastic Recovery Much quicker test Not directly tied to performance

127 Asphalt Institute TAC Position of the Technical Advisory Committee of the Asphalt Institute. It is AI s opinion that the MSCR test and specification represent a technical advancement over the current performancegraded (PG) asphalt binder specification, AASHTO M320, which will allow for better characterization of the high temperature performance-related properties of an asphalt binder.

128 Thanks! Contact Information: R. Michael (Mike) Anderson, P.E. Director of Research and Laboratory Services Asphalt Institute office