HMA Mix Design Technologies Course

Asphalt Institute Research UpdateFAA Airport Pavement Working Group MeetingApril 26, 2012Past Airfield ProjectsFairchild AFB HMA design verification in 2011 using Superpave Shear performance testRecent adjustment to test specification

Current ResearchCompleted RecentlyFHWA: WMA laboratory aging and with modulus & performance testing

Current ResearchContinued work on NCHRP Co-opWarm Mix Asphalt (WMA) binder extraction testing Long-term effect of laboratory ambient agingHow long can lab samples set before testing without changing properties? 4 days? 20 days? 80 days?RAP / RAS (recycled asphalt pavement / shingles)What effect is current practice having on mixture performance?

Current ResearchKentucky field density investigation on mixture performance (Part 2)Writing new ASTM standard for Toluene extraction and recovery of asphalt from a mixture

Current ResearchMN ROAD Cracking StudyOptimal Timing of Preventive Maintenance for Addressing Environmental Aging in Hot-Mix Asphalt PavementsMinnesota Road Research Facility pavement cores and performanceMeasure the effect of maintenance treatments on pavement aging versus depth

AcknowledgmentsTPF-5(153)Participating AgenciesMinnesota (Lead State)MarylandOhioTexasWisconsinLocal Road Research Board (LRRB)Thomas J. Wood, Lead Agency Contact

7MnROAD Low Volume Road

MnROAD Cell 24

Task 4 Cores:Recovered Binder TestingExtraction/RecoveryCentrifuge extraction using toluene/ethanolRecovery using Rotavapor2 Cores (150-mm diameter x 12.5-mm thickness)~50 grams asphaltCracking and energy tests

12.5-mmMid (B)Top (A)Bottom (C)

AAPTP 06-01Test Procedures for Predicting Non-Load Associated Cracking of Airfield HMA Pavements

PrimeAMEC Doug HansonAcknowledgmentsAirfield Asphalt Pavement Technology Program (AAPTP) Project 06-01Techniques for Prevention and Remediation of Non-Load-Related Distresses on HMA Airport PavementsAAPTP sponsors and research panelFederal Aviation AdministrationAAPTP Director Monte SymonsAAPTP 06-01 Project PanelMember Companies of the Asphalt Institute12General ConceptImpact of in-service aging is oxidation and loss of flexibility at intermediate and low temperaturesBlock-crackingwhen environmental (non-load) conditions create thermal stresses that cause strain in the asphalt mixture that exceeds the asphalts failure strainPreventing or mitigating distressidentify a property of the asphalt binder or mixture that sufficiently correlates with its flexibilityprovide a procedure to monitor when flexibility reaches a state where corrective action is needed13AAPTP 06-01 QuestionAs the Airport ManagerWhat test do I run or what calculation can I do that will tell me when the pavement is expected to begin showing significant non-load related distress? ConceptYear0102030405060708090100051015Cracking ValueCritical RangeCrackingNon-CrackingIn this example, the airport manager determines his cracking value by either calculation or test on some periodic basis probably at construction and then at 5, 8, and 10 years and every 2 years thereafter. Once the cracking value reaches a critical range, then the manager is aware that the onset of cracking, or increased cracking severity, is possible and plans for remediation can be initiated.

The concept of a critical range of values is not unusual. When Kentucky was implementing TSR, we asked Dick Root how much faith we should put in our specification value of 70%. He indicated that he was fairly confident that mixtures with TSR values greater than 80% wouldnt experience moisture damage and that mixtures with TSR values less than 60% would have moisture damage. In between is a gray area.

The question then is what test or calculation does the manager need to generate this graph?15AAPTP 06-01 PlanLab StudyAsphalt Binder StudyVarious aged conditionsAsphalt Mixture StudyVarious aged conditionsField StudyLimited validation of lab findingsAsphalt binder and mixture tests16Asphalt BindersThree asphalt binders representing different expected aging characteristicsSelected based upon the relative relationships between low temperature stiffness (S) and relaxation (m-value)West Texas Sour (PG 64-16)3.1C m-controlledGulf Southeast (PG 64-22)1.3C m-controlledWestern Canadian (PG 64-28)0.6C S-controlled17Lab Study Aging MatrixConditioning: Aging Time of BinderNo Aging (0 hours)RTFORTFO + PAV @ 20 hoursRTFO + PAV @ 40 hoursRTFO + PAV @ 80 hoursWest Canadian PG 64-28XXXXXGulf-Southeast PG 64-22XXXXXWest-Texas Sour PG 64-16XXXXXConditioning: Aging Time of Loose MixtureNo aging (0 hours)4 hours24 hours48 hoursWest Canadian PG 64-28XXXXGulf-Southeast PG 64-22XXXXWest-Texas Sour PG 64-16XXXXMastercurve Procedure y = 0.035x-0.670R = 0.8530246810121E-04Ductility at 15C, 1cm/min (cm)G/(/G) at 15C, 0.005 rad/s (MPa/s)WTXGSEWC1E-031E-021E-0119Effect of PAV Aging Time on DTc - 6.00.06.012.0020406080PAV Aging Time, HrsWTXGSE WCDifference Between Tc,m and Tc,S (C)20Relationship between DTc and Ductilityy = 7.77e-0.27xR = 0.74024681012-2.00.02.04.06.08.010.012.0Ductility at 15C, 1 cm/min (cm)Difference Between Tc,S(60) and Tc,m(60), CWTXGSEWC21Relationship between G/(h/G) and DTc1E-071E-061E-051E-041E-031E-021E-01-6.0-3.00.03.06.09.012.0Difference Between Tc,m(60) and Tc,S(60), CWest Texas SourGulf SoutheastWestern CanadianG/(/G), MPa/s22Relationship between G/(h/G) and DTc1E-071E-061E-051E-041E-031E-021E-01-6.0-3.00.03.06.09.012.0Difference Between Tc,m(60) and Tc,S(60), CWest Texas SourGulf SoutheastWestern CanadianG/(/G), MPa/s23Black Space Diagram: Western Canadian Asphalt Binder 1.00E+031.00E+041.00E+051.00E+061.00E+071.00E+081.00E+090102030405060708090Phase Angle, degreesOriginalPAV-20G*, PaPAV-40PAV-8024Mix Testing: Disk-Shaped Compact Tension Test

Disk-Shaped Compact Tension

Field Validation

Field Validation Sections 1 & 2Three general aviation (GA) airport projects representing four in-service pavementsRoundup (Montana)Recently received an overlay of an older, cracked pavementUpper layer representing the new pavement (Roundup Top)Lower layer representing the older pavement (Roundup Bottom)28Field Validation Section 3Three general aviation (GA) airport projects representing four in-service pavementsClayton (New Mexico)Paved in 2004 using 85-100 penetration asphalt binder from a local supplier (likely using West Texas Sour)Some low-severity longitudinal cracking and raveling was identified29Field Validation Section 4Three general aviation (GA) airport projects representing four in-service pavementsConchas Lake (New Mexico)Paved in 2001 using 85-100 penetration asphalt binder from same local supplier (likely using West Texas Sour)Some low-to-moderate severity raveling was identified over most of the paved areaPavement surface appeared slightly oxidized30Field Cores

Core PreparationCut top 25mm (1in) from the surface of each coreBinder testMix test

See Gayles e-mail for more details

AASHTO T319 is the modified SHRP extraction/recovery procedure. It does as well as the centrifuge extraction and Rotavapor recovery and can easily use a sample size of 1000 grams. The lower temperature/higher vacuum may help minimize additional solvent aging issues.32Relationship between G/(h/G) and Tc (with Field Cores)1E-01-6.0-3.00.03.06.09.012.0Difference Between Tc,m(60) and Tc,S(60), C Recovered1E-031E-041E-051E-061E-071E-02G/(/G), MPa/sWest Texas SourGulf SoutheastWestern Canadian33ConceptYear0102030405060708090100051015Cracking ValueCritical RangeCrackingNon-CrackingIn this example, the airport manager determines his cracking value by either calculation or test on some periodic basis probably at construction and then at 5, 8, and 10 years and every 2 years thereafter. Once the cracking value reaches a critical range, then the manager is aware that the onset of cracking, or increased cracking severity, is possible and plans for remediation can be initiated.

The concept of a critical range of values is not unusual. When Kentucky was implementing TSR, we asked Dick Root how much faith we should put in our specification value of 70%. He indicated that he was fairly confident that mixtures with TSR values greater than 80% wouldnt experience moisture damage and that mixtures with TSR values less than 60% would have moisture damage. In between is a gray area.

The question then is what test or calculation does the manager need to generate this graph?34Concept0246YearG/(/G) or TcCritical RangeCrackingNon-Cracking9E-04 MPa/s or 2.5C35Disk Shaped Compact Tension Results

Disk Shaped Compact Tension Results

Study Limitations and Future Research NeedsOnly three asphalt binders were evaluated in the laboratory studiesMay or may not represent the range of expected aging performance of asphalt binders in the United StatesNo modified asphalt binders were evaluatedThe relationships found between physical properties and aging of unmodified asphalt binders may not be valid for modified asphalt binders(N.B. modified asphalt binders may not be routinely used in GA airport asphalt pavements, rendering this limitation somewhat irrelevant).38Study Limitations and Future Research NeedsOnly three airport asphalt pavements were studied in the field validation portion of the studyFrom three airports in two sets of environmental conditionsUnfortunately, none of the four pavements exhibited high levels of cracking needed to validate the proposed parameters.39Study Limitations and Future Research NeedsThe recommended use presumes that an airport manager will have the desire, time, and resources to conduct testing and analysis throughout the pavements life.Prequalification testing of the asphalt materials could be used to identify the risk for early cracking 40Recommended FAA Research Based on Upcoming New Asphalt TechnologiesRecommend ResearchEffect of Warm Mix Asphalt (WMA) on FAA pavementsStrong presence in US and growingPotential use of drainable basesUseful to drain large paved areasTiming of preventative maintenanceThanks!

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