EvaluationoftheCombinedEffectsofReclaimedAsphaltPavement(RAP),ReclaimedAsphaltShingles(RAS),andDifferentVirginBinderSourcesonthePerformanceofBlendedBindersforMixeswithHigherPercentagesofRAPandRAS

November2015

AResearchReportfromtheNationalCenterforSustainableTransportation

ZiaAlavi,YuanHe,JohnHarvey,andDavidJones-DepartmentofCivilandEnvironmentalEngineering,UniversityofCalifornia,Davis

ReportNumber:UCPRC-RR-2015-06

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AbouttheNationalCenterforSustainableTransportationTheNationalCenterforSustainableTransportationisaconsortiumofleadinguniversitiescommittedtoadvancinganenvironmentallysustainabletransportationsystemthroughcutting-edgeresearch,directpolicyengagement,andeducationofourfutureleaders.Consortiummembersinclude:UniversityofCalifornia,Davis;UniversityofCalifornia,Riverside;UniversityofSouthernCalifornia;CaliforniaStateUniversity,LongBeach;GeorgiaInstituteofTechnology;andUniversityofVermont.Moreinformationcanbefoundat:ncst.ucdavis.edu.DisclaimerThecontentsofthisreportreflecttheviewsoftheauthors,whoareresponsibleforthefactsandtheaccuracyoftheinformationpresentedherein.ThisdocumentisdisseminatedunderthesponsorshipoftheUnitedStatesDepartmentofTransportation’sUniversityTransportationCentersprogram,intheinterestofinformationexchange.TheU.S.GovernmentandtheStateofCaliforniaassumesnoliabilityforthecontentsorusethereof.NordoesthecontentnecessarilyreflecttheofficialviewsorpoliciesoftheU.S.GovernmentandtheStateofCalifornia.Thisreportdoesnotconstituteastandard,specification,orregulation.ThisreportdoesnotconstituteanendorsementbytheCaliforniaDepartmentofTransportation(Caltrans)ofanyproductdescribedherein.Forindividualswithsensorydisabilities,thisdocumentisavailableinalternateformats.Forinformation,call(916)654-8899,TTY711,orwritetoCaltrans,DivisionofResearch,InnovationandSystemInformation,MS-83,P.O.Box942873,Sacramento,CA94273-0001.AcknowledgmentsThisstudywasfundedbyagrantfromtheNationalCenterforSustainableTransportation(NCST),supportedbyUSDOTandCaltransthroughtheUniversityTransportationCentersprogram.TheauthorswouldliketothanktheNCST,USDOT,andCaltransfortheirsupportofuniversity-basedresearchintransportation,andespeciallyforthefundingprovidedinsupportofthisproject.

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EvaluationoftheCombinedEffectsofReclaimedAsphaltPavement(RAP),

ReclaimedAsphaltShingles(RAS),andDifferentVirginBinderSourcesonthe

PerformanceofBlendedBindersforMixesWithHigherPercentagesofRAPandRAS

ANationalCenterforSustainableTransportationResearchReport

November2015

ZiaAlavi,DepartmentofCivilandEnvironmentalEngineering,UniversityofCalifornia,Davis

YuanHe,DepartmentofCivilandEnvironmentalEngineering,UniversityofCalifornia,Davis

JohnHarvey,DepartmentofCivilandEnvironmentalEngineering,UniversityofCalifornia,Davis

DavidJones,DepartmentofCivilandEnvironmentalEngineering,UniversityofCalifornia,Davis

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TableofContentsExecutiveSummary.................................................................................................................11.Introduction.......................................................................................................................3

1.1 Background..................................................................................................................31.2 ProblemStatements....................................................................................................41.3 ProjectObjectives........................................................................................................41.4 ReportLayout...............................................................................................................51.5 MeasurementUnits.....................................................................................................5

2. LiteratureReview..............................................................................................................62.1 AsphaltBinder..............................................................................................................62.2 AsphaltBinderExtraction.............................................................................................62.3 ReclaimedAsphalt........................................................................................................72.4 TestingBlendedVirgin/ReclaimedAsphaltBinders.....................................................72.5 LiteratureReviewSummary.........................................................................................9

3. ExperimentDesign..........................................................................................................113.1 ExperimentPlan.........................................................................................................113.2 AsphaltBinderTesting...............................................................................................123.3 FineAggregateMatrixTesting...................................................................................14

4. TestResults.....................................................................................................................204.1 AsphaltBinderTesting...............................................................................................204.2 FineAggregateMatrixMixTesting............................................................................26

5. ConclusionsandInterimRecommendations....................................................................37References.............................................................................................................................39

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ListofTablesTable3.1:GeneralMaterialProperties.......................................................................................11Table4.1:High,Intermediate,andLowCriticalTemperaturesofRAPBinders..........................20Table4.2:MasterCurveParametersforVirginandBlendedBinders.........................................21Table4.3:MasterCurveParametersforFAMMixes...................................................................29Table4.4:ANOVAResults............................................................................................................35ListofFiguresFigure2.1:Asphaltbindercolloidalstructure...............................................................................6Figure3.1:Exampleofmeasuredshearmodulusofablendedbinderat20°C...........................14Figure3.2:Exampleofadevelopedmastercurveforablendedasphaltbinderat20°C...........14Figure3.3:FAMspecimenscoredfromaSuperpavegyratory-compactedspecimen................16Figure3.4:Weighstationforair-voidmeasurement(a)andFAMspecimenstorage(b)...........16Figure3.5:DSR-DMAtorsionbarfixtureusedforFAMtesting...................................................17Figure3.6:ExampleFAMspecimenamplitudesweeptestresults.............................................18Figure3.7:ExampleofmeasuredshearmodulusofaFAMspecimenat20°C...........................18Figure3.8:ExampleofshearmodulusmastercurveofaFAMspecimenat20°C......................19Figure4.1:RecoveredRASbinderafterthreehoursofconditioningat190ºC...........................21Figure4.2:Shearmoduliofvirginasphaltbinders(20°C)...........................................................22Figure4.3:Shearmoduliofbinderswith25percentRAPbinderreplacement(20°C)...............23Figure4.4:Shearmoduliofbinderswith40percentRAPbinderreplacement(20°C)...............23Figure4.5:Comparisonofnormalizedshearmodulimastercurvesforblendedbinders..........24Figure4.6:GradationofFAM,RAP,andRASmaterials...............................................................26Figure4.7:FAMspecimenair-voidcontentsforPG64mixes.....................................................27Figure4.8:FAMspecimenair-voidcontentsforPG58mixes.....................................................27Figure4.9:FAMspecimenLVErangeformixeswithPG64virginbinders.................................28Figure4.10:FAMspecimenLVErangeformixeswithPG58virginbinders...............................28Figure4.11:MastercurvesofcontrolFAMmixes.......................................................................31Figure4.12:MastercurvesofFAMmixeswith25percentRAPbinderreplacement.................31Figure4.13:MastercurvesofFAMmixeswith40percentRAPbinderreplacement.................31Figure4.14:MastercurvesofFAMmixeswith15percentRASbinderreplacement.................31Figure4.15:PG64-16-A:ShearandnormalizedmodulusmastercurvesofFAMmixes............32Figure4.16:PG58-22-A:ShearandnormalizedmodulusmastercurvesofFAMmixes............32Figure4.17:PG64-16-B:ShearandnormalizedmodulusmastercurvesofFAMmixes............33Figure4.18:PG58-22-B:ShearandnormalizedmodulusmastercurvesofFAMmixes............33Figure4.19:PG64-16-C:ShearandnormalizedmodulusmastercurvesofFAMmixes............34Figure4.20:ComparisonofasphaltbinderandFAMmixshearmodulus(0.1Hzat20°C).........36Figure4.21:ComparisonofasphaltbinderandFAMmixshearmodulus(1.0Hzat20°C).........36Figure4.22:ComparisonofasphaltbinderandFAMmixshearmodulus(10Hzat20°C)..........36

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ListofAbbreviationsAASHTO AmericanAssociationofStateHighwayandTransportationOfficialsAB AssemblybillANOVA AnalysisofvarianceBBR BendingbeamrheometerCaltrans CaliforniaDepartmentofTransportationDMA DynamicmechanicalanalyzerDSR DynamicshearrheometerFAM FineaggregatemixFHWA FederalHighwayAdministrationG* DynamicshearmodulusGmB BulkspecificgravityofthemixGmm TheoreticalmaximumspecificgravityofthemixHMA HotmixasphaltLVE LinearviscoelasticNCHRP NationalCooperativeHighwayResearchProgramn-PB NormalpropylbromideNCST NationalCenterforSustainableTransportPAV PressureagingvesselPG PerformanceGradingPPRC PartneredPavementResearchCenterRA RejuvenatingagentRAP ReclaimedorRecycledAsphaltPavementRAS ReclaimedorRecycledAsphaltShinglesRTFO Rollingthin-filmovenSARA Saturates,aromatics,resins,andasphaltenesSHRP StrategicHighwayResearchProgramSPE StrategicPlanElementSUPERPAVE SuperiorPerformingAsphaltPavementTCE TrichloroethyleneUCPRC UniversityofCaliforniaPavementResearchCenterWMA Warmmixasphaltδ Phaseangle

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TestMethodsCitedintheTextAASHTOM320 StandardSpecificationforPerformance-GradedAsphaltBinderAASHTOR30 StandardPracticeforMixtureConditioningofHotMixAsphalt(HMA)AASHTOR35 StandardPracticeforSuperpaveVolumetricDesignforAsphaltMixturesAASHTOT30 StandardMethodofTestforMechanicalAnalysisofExtractedAggregateAASHTOT164 StandardMethodofTestforQuantitativeExtractionofAsphaltBinderfrom

HotMixAsphaltAASHTOT166 StandardMethodofTestforBulkSpecificGravity(Gmb)ofCompactedHot

MixAsphalt(HMA)UsingSaturatedSurface-DrySpecimensAASHTOT209 StandardMethodofTestforTheoreticalMaximumSpecificGravity(Gmm)

andDensityofHotMixAsphaltAASHTOT240 StandardMethodofTestforEffectofHeatandAironaMovingFilmof

AsphaltBinder(RollingThin-FilmOvenTest)AASHTOT269 StandardMethodofTestforPercentAir-voidsinCompactedDenseand

OpenAsphaltMixturesAASHTOT308 StandardMethodofTestforDeterminingtheAsphaltBinderContentofHot

MixAsphalt(HMA)bytheIgnitionMethodAASHTOT312 StandardMethodofTestforPreparingandDeterminingtheDensityof

AsphaltMixSpecimensbyMeansoftheSuperpaveGyratoryCompactorAASHTOT313 StandardMethodofTestforDeterminingtheFlexuralCreepStiffnessof

AsphaltBinderUsingtheBendingBeamRheometerAASHTOT315 StandardMethodofTestforDeterminingtheRheologicalPropertiesof

AsphaltBinderUsingaDynamicShearRheometer(DSR)ASTMD1856 StandardTestMethodforRecoveryofAsphaltfromSolutionbyAbson

Method

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ConversionFactors

SI*(MODERNMETRIC)CONVERSIONFACTORSAPPROXIMATECONVERSIONSTOSIUNITS

Symbol WhenYouKnow MultiplyBy ToFind SymbolLENGTH

in inches 25.4 Millimeters mmft feet 0.305 Meters myd yards 0.914 Meters mmi miles 1.61 Kilometers Km

AREAin2 squareinches 645.2 Squaremillimeters mm2ft2 squarefeet 0.093 Squaremeters m2yd2 squareyard 0.836 Squaremeters m2ac acres 0.405 Hectares hami2 squaremiles 2.59 Squarekilometers km2

VOLUMEfloz fluidounces 29.57 Milliliters mLgal gallons 3.785 Liters Lft3 cubicfeet 0.028 cubicmeters m3yd3 cubicyards 0.765 cubicmeters m3

NOTE:volumesgreaterthan1000Lshallbeshowninm3MASS

oz ounces 28.35 Grams glb pounds 0.454 Kilograms kgT shorttons(2000lb) 0.907 megagrams(or"metricton") Mg(or"t")

TEMPERATURE(exactdegrees)°F Fahrenheit 5(F-32)/9 Celsius °C

or(F-32)/1.8 ILLUMINATION

fc foot-candles 10.76 Lux lxfl foot-Lamberts 3.426 candela/m2 cd/m2

FORCEandPRESSUREorSTRESSlbf poundforce 4.45 Newtons Nlbf/in2 poundforcepersquareinch 6.89 Kilopascals kPa

APPROXIMATECONVERSIONSFROMSIUNITSSymbol WhenYouKnow MultiplyBy ToFind Symbol

LENGTHmm millimeters 0.039 Inches inm meters 3.28 Feet ftm meters 1.09 Yards ydkm kilometers 0.621 Miles mi

AREAmm2 squaremillimeters 0.0016 squareinches in2m2 squaremeters 10.764 squarefeet ft2m2 squaremeters 1.195 squareyards yd2ha Hectares 2.47 Acres ackm2 squarekilometers 0.386 squaremiles mi2

VOLUMEmL Milliliters 0.034 fluidounces flozL liters 0.264 Gallons galm3 cubicmeters 35.314 cubicfeet ft3m3 cubicmeters 1.307 cubicyards yd3

MASSg grams 0.035 Ounces ozkg kilograms 2.202 Pounds lbMg(or"t") megagrams(or"metricton") 1.103 shorttons(2000lb) T

TEMPERATURE(exactdegrees)°C Celsius 1.8C+32 Fahrenheit °F

ILLUMINATIONlx lux 0.0929 foot-candles fccd/m2 candela/m2 0.2919 foot-Lamberts fl

FORCEandPRESSUREorSTRESSN Newtons 0.225 Poundforce lbfkPa Kilopascals 0.145 poundforcepersquareinch lbf/in2

*SIisthesymbolfortheInternationalSystemofbemadetocomplywithSection4ofASTME380(RevisedMarch2003)

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ExecutiveSummary

ThisreportsummarizesthemainfindingsfromaprojectfundedbytheNationalCenterforSustainableTransportation(NCST)toinvestigatetheuseofhigherpercentagesofreclaimedasphaltpavement(RAP)andreclaimedasphaltshingles(RAS)asareplacementforapercentageofthevirginbinderinnewasphaltmixesinCalifornia.Theresearchfocusedontestingproceduresthatdonotfirstrequirechemicalextractionandrecoveryoftheage-hardenedasphaltbindersfromtheRAPandRAS.Fivedifferentasphaltbinderscoveringtwoperformancegrades(PG64-16andPG58-22)andsourcedfromthreeCaliforniarefinerieswereevaluatedinthisstudy.TheinfluenceoftwodifferentpercentagesofRAP(25and40percentbybinderreplacement)andonepercentageofRAS(15percentbybinderreplacement)wereevaluatedthroughpartialfactorialasphaltbindertestingandfullfactorialfineaggregatematrix(FAM)mixtesting.Theeffectofapetroleum-basedrejuvenatingagentaddedtoselectedmixes(with40percentRAPand15percentRAS)wasalsoinvestigated.Testingwaslimitedtotheintermediatetemperaturepropertiesofthemixes(i.e.,4°Cto40°C).Keyobservationsandfindingsfromthisprojectincludethefollowing:

• AsphaltbinderextractedandrecoveredfromRAScouldnotbetestedduetoitsveryhighstiffness.TheRASbinderwasnotsufficientlyworkabletomoldsamplesfortestinginadynamicshearrheometer(DSR).

• Testingproceduresweredevelopedaspartofthispreliminarytestingphasetomeasuredynamicshearmodulusatdifferenttemperaturesandfrequencies,andamethodforpreparingandtestingFAMmixspecimenswasdeveloped.Cylindricalspecimens0.5in.(12.5mm)indiametercoredfromaSuperpavegyratory-compactedFAMmixspecimenweretestedusingatorsionbarfixtureinaDSR.PreliminarytestingofFAMmixespreparedwithmaterialspassingthe#4,#8,or#16(4.75mm,2.36mm,or1.18mm)sievesindicatedthatthisapproachisrepeatableandreproducible,andproducesrepresentativeresultsforcharacterizingtheperformancerelatedpropertiesofcompositebinderatbinderreplacementratesupto40percentandpossiblyhigher.Useofmaterialspassingthe#8sieve(2.36mm)isrecommended.

• TheeffectofRAPinincreasingthestiffnessofblendedbinderswasdependentprimarilyontheasphaltbindergradeand,toalesserextent,bythesourceofasphaltbinder.

• StatisticalanalysesofthetestresultsindicatedthatRAPandRAScontent,asphaltbindergradeandsource,andrejuvenatingagentallhadasignificantinfluenceonFAMmixstiffness,asexpected.

• TheFAMmixescontainingRASshowedsimilarstiffnessestothecorrespondingcontrolmixes(i.e.,containingnoreclaimedmaterials),suggestingthattheRASbinderdidnoteffectivelyblendwiththevirginbinderatthetemperaturesandmixingdurationsusedinthisstudy.

• TheinfluenceofrejuvenatingagentonreducingtheblendedbinderandFAMmixstiffnesseswasevident.Additionaltesting(beyondthescopeofthisstudy)isrequiredtoevaluatethelong-termbehaviorofmixesproducedwithrejuvenatingagentsto

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determinewhetherthebenefitsarelimitedtoproductionandearlylife,orwhethertheyextendthroughthedesignlifeofthelayer.

• ReasonablecorrelationswereobservedbetweenthestiffnessesofasphaltbinderandthestiffnessesofFAMmixesattestingfrequenciesrangingfrom0.1Hzto10Hz.DiscrepanciesbetweenthetwomeasuredstiffnessesmaybeanindicationthatcompleteblendingofthevirginandreclaimedasphaltbinderswasnotachievedintheFAMmix,butwasforcedduringthechemicalextractionandrecovery.Thiswarrantsfurtherinvestigation.

Basedonthefindingsfromthisstudy,FAMmixtestingisconsideredtobeapotentiallyappropriateprocedureforevaluatingthepropertiesofblendedasphaltbinderinmixescontainingrelativelyhighquantitiesofRAPandRAS.Furthertestingonawiderrangeofasphaltbindergrades,asphaltbindersources,andRAPandRASsourcesisrecommendedtoconfirmthisconclusionandtodevelopmodelsforrelatingbinderpropertiesdeterminedfromFAMmixtestingtothosedeterminedfromconventionalperformancegradetesting.Chemicalanalysesofblendedbindersmayprovideadditionalinsightsforinterpretingtestresultsandwarrantfurtherinvestigation.

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1.Introduction

1.1 Background

Morethan90percentoftheroadandhighwaynetworkintheUnitedStatesispavedwithasphaltconcrete.Thesepavementsrequireregularmaintenanceandperiodicrehabilitationtoperformeffectivelyunderheavyrepetitivetrafficloadsandsevereenvironmentalconditions.Thismaintenanceandrehabilitationinturnrequiresacontinuoussupplyofaggregateandasphaltbinder,bothofwhicharebecomingincreasinglyscarceandmoreexpensive.Consequently,thereisgrowinginterestintheuseofreclaimedasphaltpavement(RAP)materialsintheproductionofnewasphaltmixestoreducecostsandpreservenonrenewableresources.Toencouragethischange,theFederalHighwayAdministration(FHWA)recyclingpolicystatesthatthematerialsoriginallyusedintheconstructionofpavementscanbereusedfortheirrepair,reconstruction,andmaintenance(1).Reclaimedasphaltroofingshingles(RAS)areanotherpotentiallyvaluablesourceofasphaltbinderforuseinpavementconstructionsincetheycontainbetween20and30percentasphaltbinderbyweightoftheshingle.ThemajorityofRASproducedintheUnitedStates(approximately10milliontonsperyear)isobtainedfromusedroofshingles(i.e.,tear-offshingles).About1milliontonsofRASisobtainedfromproductionrejects(2).Duringasphaltshingleproduction,thebinderisheavilyoxidizedduringanair-blowingprocess.Additionalagingoccursovertimeastheshinglesareexposedtothesunandprecipitationandsubjectedtodailyandseasonaltemperatureextremes.Consequently,thebinderishighlyagedbythetimethatitisusedinnewmixes,andalthoughbindercontentsintheshinglesarehigh,thepropertiesofthebinderareverydifferentfromthoserecoveredfromRAP,particularlyforthemoreheavilyagedtear-offshingles.RAPandRASstockpilesareusuallyhighlyvariableintermsofbindercontent,binderproperties,andbinderconditionduetothediversesourcesofthematerialsandthemethodsusedtoreclaimthem.Theyarealsooftencontaminatedwithotherconstructionwaste,whichmayfurtherinfluencethewaytheybehaveinnewasphaltmixes.TheCaliforniaDepartmentofTransportation(Caltrans)recentlyincreasedto25percenttheallowablepercentageofreclaimedasphaltpavement(RAP)thatcanbeusedinnewasphaltmixes.ACaltrans-industrytaskgroup,formedtoconsiderrecentlegislation(AB812)coveringtheuseofRAPinnewmixes,hasproposedallowinganincreaseofupto40percentvirginbinderreplacementfromacombinationofRAPandRAS.Thesechangescanreducetheamountofvirginbinderrequiredinnewmixes,androadagenciesandcontractorscanthereforepotentiallycontributetoincreasedsustainabilityofpavementsbyeffectivelyusingRAPandRASmaterialsinnewasphaltmixes.However,concernshavebeenraisedregardingtheinfluencethattheagedbinderinRAPandRASwillhaveonthenewbinderproperties.Theeffectofthesematerialsonthelong-termbehaviorandperformanceofasphaltconcretemixesneedstobefullyunderstoodtoensurethatprematurefailuresresultingfromineffectiveblendingoracceleratedagingdonotoccur.

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1.2 ProblemStatements

Whilevirginmaterialsourcesforpavementapplicationsarebecomingincreasinglyscarce,thevolumeofpavementmaterialroutinelyreclaimedfromin-servicepavementsisincreasing.Consequently,thereisgrowinginterestinusingsignificantlyhigherquantitiesofRAPandRASinCaltransasphaltmixdesigns.However,makingthischangehasraisedconcernsregardinghowthesecompositebindersmayinfluencetheperformanceanddurabilityofasphaltmixesunderCaliforniatrafficandenvironmentalconditions.Thefollowingproblemstatementshavebeenidentifiedandrequireeitheradditionalresearchorrefinement/calibrationforCaliforniaconditions:

• TheeffectofRAPand/orRASontheperformancegradeofcompositebindersisunknownandneedstobeaddressed.BothgeneraleffectsandtheeffectsofspecificRAPandRASsourcesneedtobeinvestigated.

• Theprocessofrecoveringasphaltbindersfromasphaltmixesinvolvesrelativelyaggressivechemistrythatmayinfluencetheblendingofoldandvirginbinders.Thepotentialeffectsofthisneedtobeconsideredwhentestingtheperformancepropertiesofrecoveredbinders.

• TheperformanceofasphaltmixescontainingRAPand/orRASisdependentonthepropertiesoftheconstitutivecomponents.Thesepropertiesdependonthechemistryofthebinders(whichdependsoncrudeoilsource),changesduringtimeinserviceafterbothshort-andlong-termaging,anddiffusionoftheoldandnewbindersovertime.Consequently,thecurrentSuperpavetestingequipmentandproceduresmayneedtobeadaptedtoaccuratelycharacterizetherheologicalpropertiesofthecompositebinderwithrespecttohigh-,intermediate-,andlow-temperatureperformance.

• Theeffectsofmixproductiontimeandtemperatureonthedegreeofblendingandonthepropertiesofthecompositebinderneedtobequantified.

• Theeffectsofrejuvenatingagentsontheblendingofagedandnewbindersandthelong-termperformanceofmixesneedtobeevaluated.

1.3 ProjectObjectives

Theobjectiveofthisproject,fundedbytheNationalCenterforSustainableTransportation(NCST),wastoinvestigateusinghigherpercentagesofreclaimedasphaltpavement(RAP)andreclaimedasphaltshingles(RAS)asareplacementforapercentageofthevirginbinderinnewasphaltmixesinCalifornia.Thisobjectivewasachievedthroughthefollowingtasks:

1. Areviewoftheliteratureonresearchrelatedtothetopic,withspecialemphasisontheworkoftheFederalHighwayAdministration(FHWA)andonrecentNationalCooperativeHighwayResearchProgram(NCHRP)projects

2. DevelopmentofaworkplantoevaluatetheeffectofvirginbindersourceandcharacteristicsonpropertiesofcompositebinderscontainingdifferentpercentagesofRAPand/orRAS

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3. Developmentofarobustandreliabletestingprocedureforevaluatingthehigh-temperaturepropertiesoffineaggregatematrix(FAM)mixesusingasolidtorsionbarfixtureinadynamicshearrheometer(DSR).Low-temperaturepropertiesarebeinginvestigatedinaseparatestudy

4. Evaluationofthehigh-temperaturerheologicalpropertiesofcompositeFAMmixeswithdifferentvirginbindersourcesatdifferentRAPand/orRASpercentages

5. Statisticalanalysisofthetestresults

6. PreparationofasummaryreportandpreliminaryrecommendationsforaddressingtheeffectofvirginbindersourceontheperformanceofcompositebinderswhenincorporatingRAPand/orRASinnewasphaltmixes

Thisreportdocumentstheworkcompletedonalltasks.Itshouldbenotedthatthisprojectwascarriedoutasonepartofalarger,comprehensiveresearchinitiativeintotheuseofhighquantitiesofRAPandRASinnewasphaltmixesinroadandairfieldpavements.OtherparticipantsincludetheCaliforniaDepartmentofTransportation,theCaliforniaDepartmentofResourcesRecyclingandRecovery,andtheFederalAviationAdministration.1.4 ReportLayout

Thisresearchreportpresentsanoverviewoftheworkcarriedoutinmeetingtheobjectivesofthestudy,andisorganizedasfollows:

• Chapter2providesanoverviewoftheliteraturerelatedtothetopic.

• Chapter3summarizestheexperimentplananddescribesthematerialsandtestingmethodologyused.

• Chapter4presentstestresultsandassociateddiscussion.

• Chapter5providesconclusionsandpreliminaryrecommendations.

1.5 MeasurementUnits

AlthoughCaltransrecentlyreturnedtotheuseofU.S.standardmeasurementunits,theSuperpavePerformanceGrading(PG)Systemisametricstandardandusesmetricunits.Inthistechnicalmemorandum,bothEnglishandmetricunits(providedinparenthesesaftertheEnglishunits)areprovidedinthegeneraldiscussion.MetricunitsareusedinthereportingofPGtestresults.Aconversiontableisprovidedonpageviii.

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2. LiteratureReview

2.1 AsphaltBinder

Asphaltbinderisobtainedfromthedistillationofcrudeoilandisablendofcomplexhydrocarbonscontainingthousandsofdifferentmolecules(3).Morethan90percentofasphaltbinderconsistsofcarbonandhydrogenwiththeremainderconsistingofheteroatoms(sulfur,hydrogen,andnitrogen)andafewmetallicelements(e.g.,vanadium,nickel,andiron).Thepolarmoleculesofasphaltbindercanbecategorizedintofourmainfractions,namelysaturates,aromatics,resins,andasphaltenes(i.e.,SARAfractions).ThechemicalcompositionandproportionsoftheSARAfractionsaredependentonthesourceofthecrudeoilandontherefiningprocessusedtoproducethebinder(3,4).Asphalteneshavethehighestpolarityandmolecularweight,followedbyresins,aromatics,andsaturates(3).Thesefourmaincompoundscanbeassembledinacolloidalstructuretomodelthepropertiesandperformanceofasphaltbinder.Asphalteneformsthecore,whichiscoveredbyresinsthatarebridgedtoaromaticsanddispersedinsaturates,asshowninFigure2.1(4).Asphaltbinderstiffnessandstrengthpropertiesaregenerallyrelatedtoasphaltenesandresins,whileviscousandplasticizingpropertiesaregenerallyrelatedtothearomaticsandsaturates(5).Therheologicalanddesiredperformancepropertiesofasphaltbinderarethereforedependentonthepropertiesoftheindividualfractionsandtheirproportions,whichchangeoverthelifeofapavementduetooxidation,volatilization,andotherweatheringmechanisms.

Figure2.1:Asphaltbindercolloidalstructure.

2.2 AsphaltBinderExtraction

Anumberofstudieshavebeenconductedtoevaluatedifferentsolventsandmethodsfortheextractionandrecoveryofasphaltbinderfrommixes(6,7-10).Petersenetal.(11)evaluateddifferentsolventtypes(trichloroethylene[TCE],toluene/ethanol,andaproprietaryproductknownasEnSolve)andthreecombinationsofextractionandrecoverymethods(centrifuge-Abson,centrifuge-Rotavapor,andSHRP[StrategicHighwayResearchProgram]method-Rotavapor),andfoundtherewasnosignificantdifferencebetweensolventtypeormethod

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whendeterminingtheasphaltbindercontentandrheologicalpropertiesoftherecoveredbinder.Anotherstudyusingthereflux–RotovaporrecoverymethodalsodemonstratedthatbinderextractedusingeitherTCEorEnSolvehadrelativelysimilarproperties(9).AstudybyStroup-Gardineretal.(12)foundthatusingnormalpropylbromide(n-PB)asanalternativechemicalsolventcanreducetheamountofagingoftheasphaltbinderduringextractionandrecoverywhencomparedtoTCE.Thestudyalsofoundthatthedeterminedbindercontentwasnotinfluencedbysolventtype.However,incompatibilitiesbetweenvarioustypesofpropylbromideandpolymer-modifiedbinderswererecognized.2.3 ReclaimedAsphalt

RAPmaterialshavebeenusedinsmallquantitiesinnewmixesformanyyears.However,inthepastthismaterialhasbeenconsideredonlyasareplacementforvirginaggregate(i.e.,“blackrock”)andnotasapartreplacementforvirginasphaltbinder.ConsequentlythepotentialbinderreplacementandpropertiesoftheagedRAPbinderwerenottakenintoaccountinnewmixdesigns.ThisgenerallydidnotresultinanyproblemsaslongasthepercentageofRAPwaskeptbelowapproximately15percent,aswascommoninmanystatesincludingCaliforniauntilrecently.Recentstudiesandfieldobservations(6,13-15)havedemonstratedthattheagedbinderinreclaimedmaterialscanblendappreciablywithvirginbinder,allowingforbinderreplacementtobeconsideredifRAPandRASareaddedtothemix.However,thepropertiesofthevirginbinderwillbealteredbytheagedRAPandRASbinders,whichcouldinturninfluencetheperformanceofamixintermsofrutting,cracking,raveling,and/ormoisturesensitivity.2.4 TestingBlendedVirgin/ReclaimedAsphaltBinders

2.4.1 IntroductionTodate,themajorityofstudiesonthecharacterizationanddesignofasphaltmixescontainingRAPand/orRASinvolveextractionandrecoveryofasphaltbinderfromthemixusingchemicalsolvents(6,13,14,16-24).Theextractionandrecoverymethodhaslongbeencriticizedforbeinglaborintensive,forpotentiallyalteringbinderchemistryandrheology,andforcreatinghazardouschemicaldisposalissues.Studieshavealsodemonstratedthatsomeoftheagedbindermaystillremainontheaggregateafterextraction,andthusthemeasuredpropertiesfromtheextractedandrecoveredbindermaynotbecompletelyrepresentativeoftheactualpropertiesofthebinderinthemix(11,14).Asphaltbindercanalsostiffenafterextractionduetopotentialreactionsbetweenthebindercompoundsandthesolvent(25).Typically,theextractionprocessalsoblendsagedandvirginbindersintoahomogenouscompositebinderthatmaynotbetrulyrepresentativeoftheactualcompositebinderinthemixafterproduction.RAPandRASstockpilesaretypicallyhighlyvariablebecausetheycontainmaterialsreclaimedfromnumerouslocations.Consequently,obtainingrepresentativebindersforresearch-basedlaboratorytestingbyusingchemicalextractionandrecoveryisnotpossible.Conventionalpracticeforconductinglaboratorytestinghasthereforebeentoproducesimulatedasphaltbindersundercontrolledmixingandagingconditionsasawayofprovidingsomelevelofconsistencyforbetterunderstandingkeyaspectsofthetestingofcompositebinders(26,27).

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Twoalternativemethodstosolventextractionandrecoveryhavebeeninvestigatedforcharacterizingthepropertiesofblendedbinders,namelytestingasphaltmortarortestingonlythefineaggregatematrixofamix.Initialresultscitedintheliteratureforthesealternativetestingapproachesindicatethattheyareappropriateandjustifyfurtherinvestigation(28-34).2.4.2 AsphaltMortarTestingAsphaltmortartestsareconductedusingtwomortarsamples:onecontainingvirginbinderplusRAP,andonecontainingonlyvirginbinderplustheaggregatesobtainedfromprocessingRAPinanignitionoven(i.e.,theRAPbinderisburnedoffintheignitionoven).Conceptually,ifthetotalbindercontentsandaggregategradationsareexactlythesameforbothsamples,thedifferencesbetweentherheologicalandperformancepropertiesofthetwosamplescanbeattributedtotheRAPbinder(28-30).Anumberofstudieshavebeenconductedusingthisapproachwithdynamicshearrheometer(DSR)andbendingbeamrheometer(BBR)testingtoassessthestiffnessofthesamplesathighandlowtemperatures,respectively(28-30).Maetal.(28)developedaBBRtestingprocedureforasphaltmortarspecimensmadewithsinglesizeRAPmaterial(100percentpassingthe#50sieve[300µm]andretainedonthe#100sieve[150µm]).Basedontherelationshipbetweentheasphaltbinderandasphaltmortarproperties,thelowPGgradeoftheRAPbindercouldbeestimatedwithouttheneedforextractionandrecoveryofthebinder.Theasphaltmortarsamplesevaluatedinthatstudyhadamaximumof25percentbinderreplacementusingtheRAP.Swierzetal.(28)continuedthisworkandfoundthattheBBRtestonasphaltmortarwassufficientlysensitivetodistinguishbetweendifferentRAPsourcesandcontentsinblendedbindersupto25percentbinderreplacement.AsphaltmortarsamplescontainingonlyRAS(upto40percentbinderreplacement)andacombinationofRAPandRASwerealsoevaluatedinthestudy.TheworkculminatedinthedevelopmentofablendingchartthatestimatesthePGgradeoftheblendedbinderinamixbasedontherespectiveRAPandRASpercentages.Hajjetal.(7)comparedtheperformancegradepropertiesofblendedbinderbyusingDSRandBBRtestingofbothrecoveredbinderandasphaltmortar.TheresultswerefoundtobedependentontheamountofRAPinthemix,andalthoughtheresultsofmixeswithupto50percentRAPshowedsimilartrends,themeasuredhigh,intermediate,andlowcriticaltemperaturesofthemortarwerelowerthanthosemeasuredontheextractedbinder.ThedifferencesinresultsincreasedwithincreasingRAPcontent.Thereasonsforthedifferenceswerenotforensicallyinvestigated,butwereattributedinparttotheinfluenceoftheextractionchemistryonfullblendingofthebindersandpossiblytotheeffectofthechemistryonadditionalhardeningofthebinders.PreliminarytestingattheUCPRC(35)foundthatasphaltmortarsamplespreparedwithasphaltbinderandveryfineaggregate(passingthe#50[300µm]andretainedonthe#100[150µm]sieves)weresufficientlyworkabletoconductDSRtestingprovidedthatthebinderreplacementratedidnotexceed25percent.MortarswithhigherbinderreplacementrateswereunworkableandcouldnotbetestedinaDSR.Thestudyconcludedthatalthoughthemortartestdeservesfurtherinvestigation,itmaynotbeappropriatefortestingsampleswithhighbinderreplacementrates(i.e.,>25percent).

9

2.4.3 FineAggregateMatrix(FAM)MixTestingTestingFAMmixesasanalternativetotestingasphaltmortarhasalsobeeninvestigated(8-10).FAMmixesareahomogenousblendofasphaltbinderandfineaggregates(i.e.,passinga#4,#8,or#16[4.75mm,2.36mm,or1.18mm]sieve).TheasphaltbindercontentandthegradationoftheFAMmustberepresentativeofthebindercontentandgradationofthefineportionofafull-gradedasphaltmix.SmallFAMcylindricalbarscanbetestedwithasolidtorsionbarfixtureinaDSR(knownasadynamicmechanicalanalyzer[DMA]).Thistestingapproachissimilartothatusedforasphaltmortarsinthattwosamplesaretested,onecontainingvirginbinderplusRAP,andthesecondcontainingvirginbinderplustheaggregatesobtainedfromprocessingRAPinanignitionoven.AnydifferencesintheresultscanthenbeattributedtotheRAP/RAScomponentoftheFAM.Kanaan(30)evaluatedtheviscoelastic,strength,andfatiguecrackingpropertiesofFAMspecimenswithdifferentamountsofRAS.TheresultsshowedthatFAMtestingdetecteddifferencesinthepropertiesevaluatedamongthevariousmixes,andspecificallythatthestiffnessandstrengthofasphaltmixesincreasedwithincreasingRAScontent.Understrain-controlmode,thefatiguelifeoftheFAMspecimensdecreasedwithincreasingRAScontent,whileunderstress-controlmode,oppositetrendswereobserved.2.4.4 QuantifyingLevelofDiffusionandBlendingAnumberofstudieshavebeenundertakenrecentlytobetterunderstandthediffusionandblendingofagedandvirginbinders.Yaretal.(27)evaluatedandquantifiedtheeffectsoftimeandtemperatureondiffusionrateandtheultimateblendingoftheagedandvirginbindersthroughanexperimental-basedapproachvalidatedwithanalyticalmodelingofdiffusion.Thechangesinthestiffnessofacompositetwo-layerasphaltbinderspecimen(alsoknownasawaferspecimen)weremonitoredinDSRtests.Thewaferspecimenwascomposedoftwo1mmthickasphaltdisksmadewithsimulatedRAPbinderandvirginbinder,respectively.ThisstudyrevealedthatthediffusioncoefficientbetweentwobindersincontactcanbeestimatedfromDSRtestresultsandthatthediffusionmechanismcanbemodeled(i.e.,Fick’ssecondlawofdiffusion).Thediffusionratewasfoundtoincreasewithtemperature,buttheratewasinfluencedbybinderchemistry.Onlylimiteddiffusionandblendingoccurredattemperaturesbelow100°C.Consequently,productiontemperatureandtimeswillneedtobeappropriatelyselectedatasphaltplantstoensuresufficientblendingbetweenthevirginbinderandagedRAPbinder.Krizetal.(31)completedasimilarstudywithsimilarfindings.2.5 LiteratureReviewSummary

KeylearningpointsfromtheliteraturereviewrelevanttothisUCPRCstudyincludethefollowing:

• TheasphaltbinderinRAPandRAScanblendappreciablywithvirginbinderinnewmixes.Thelevelofblendingbetweentheagedandnewbindersdependsonthechemicalcompositionoftheindividualbinders.Thecompatibilityofreclaimedandvirginasphaltbindersfromdifferentsourcesandwithdifferentperformancegradesmustbewellunderstoodtoensureoptimalperformanceofasphaltmixescontaininghighquantitiesofreclaimedasphalt.

10

• Appropriatemethodsforextractingagedbinderfromreclaimedasphaltmaterialsarestillbeingdevelopedandarefocusingontheeffectsofextractionsolventsonthepropertiesofrecoveredbinders.Thesolventscurrentlybeingusedareconsideredtobesufficientlyaggressivetofullyblendagedandvirginbindersextractedfromnewmixes,therebypotentiallyprovidingmisleadingbinderreplacementvaluesandnonrepresentativePGgradingsofblendedbinders.

• AlternativemethodstoextractionandrecoveryarebeingexploredtobettercharacterizetheperformancepropertiesofvirginbindersblendedwiththeagedbindersinRAPandRAS.TestsonmortarandFAMmixeswarrantfurtherinvestigation.

11

3. ExperimentDesign

ThisUCPRCstudyfocusedonevaluatingtheeffectofvirginbindersourceandperformancegradeontheperformancepropertiesofblendedbinderinmixeswithhighquantitiesofRAP(i.e.,≥25percent)andRAS.Thischapterdescribestheexperimentplanandthetestingandevaluationmethodologiesusedinthisstudy.3.1 ExperimentPlan

Theexperimentplanincludedthefollowingthreemaintasks:• Determinetherheologicalpropertiesofthevirginbinders,recoveredRAPbinder,

recoveredRASbinder,andtheblendedbindersatvariousbinderreplacementrates.Testsinclude:+ Performancegrading+ Frequencyandtemperaturesweepteststodevelopmastercurves

• Determinetherheologicalpropertiesoffineaggregatematrix(FAM)mixescontainingdifferentamountsofrecoveredRAPandRAS(bybinderreplacementrates)andvariousvirginbinders.Testsinclude:+ Amplitudesweepstraintesttodeterminethelinearviscoelasticregion+ Frequencyandtemperaturesweepteststodevelopmastercurves

• ComparetheresultsofasphaltbinderandFAMmixtestsusingdifferentanalysistechniquesincludingstatisticalevaluationofsignificantfactors

3.1.1 MaterialSamplingandTestingFactorialTable3.1summarizesthesamplingandtestingfactorialforthematerialsusedinthisstudy.ThreebindergradesweresampledfromthreedifferentCaliforniarefineriesthatusethreedifferentprimarycrudeoilsources.Therejuvenatingagentwasobtainedfromoneoftherefineries.

Table3.1:GeneralMaterialPropertiesFactor Factorial

LevelDetails

Asphaltbindersourceandgrade 5 PG64-16andPG58-22(sourcedfromRefinery-A)PG64-161andPG58-22(sourcedfromRefinery-B)PG64-16(sourcedfromRefinery-C)

Aggregatetype 1 GraniticRAPsource 1 SacramentoRASsource 1 Tear-offshingles(Oakland)RAPcontent(bybinderreplacement) 3 0%(allfivebinderstested)

25%(allfivebinderstested)40%(twoRefinery-Abinderstested)

RAScontent 1 5%totalweightofmix(~15%bybinderreplacement)Rejuvenatingagent 1 Petroleumbase(sourcedfromRefinery-C)

12%byweightoftotalbinderusedinthemix1NotethatalthoughPG64-16binderwasrequestedfromRefinery-B,thebindersuppliedmettherequirementsforPG64-22

12

3.2 AsphaltBinderTesting

3.2.1 PerformanceGradingofExtractedBinderIn2001,investigatorsintheNCHRP9-12project(6)proposedguidelinesfortheuseofRAPintheSuperpavemixdesignmethod.TheseproposedguidelinesrequiredeterminationoftheperformancegradeoftheRAPbinderformixescontainingmorethan25percentRAPtoensurethatanappropriatevirginbinderperformancegradecanbeaccuratelyselectedfromablendingchart.Thefollowingprocedure,proposedintheNCHRPstudyguidelines,wasusedfordeterminingtheperformancegrade(PG)ofthereclaimedasphalt(RAPorRAS)bindersusedintheUCPRCstudy:Asphaltbinderextractionandrecovery

1. Obtainarepresentativesampleofreclaimedasphaltmaterial(about1,000g)thatwillprovideapproximately50to60gofrecoveredbinder(assuming5percentRAPbindercontent).

2. ExtractandrecovertheasphaltbinderfromthereclaimedasphaltfollowingtheAASHTOT164procedure.Tolueneorn-propylbromidemaybeusedasthechemicalsolvent.Documenttheuseofanyothersolventsonthetestsheet.Nitrogenblanketingisrecommendedtopreventundesiredbinderoxidationduringextraction.

Asphaltbinderperformancegrading

1. DeterminetheperformancegradeoftheextractedreclaimedasphaltbinderaccordingtoAASHTOM320.Rotationalviscometer,binderflashpoint,massloss,andpressureagingvessel(PAV)arenotrequiredforreclaimedasphaltbindergrading.PAVagingisnotnecessarygiventhatthereclaimedasphaltbinderhasalreadybeenagedinthepavement(forRAP)oronaroof(forRAS).

2. Performadynamicshearrheometer(DSR)testwith25mmparallelplategeometryontherecoveredreclaimedasphaltbinder(AASHTOT315)todeterminethecriticalhightemperatureofthebinder(temperatureatwhichG*/sin(δ)is1.0kPa).

3. Agetheextractedreclaimedasphaltbinderinarollingthin-filmoven(RTFO,AASHTOT240).

4. PerformaDSRtestwith25mmparallelplategeometryontheRTFO-agedrecoveredreclaimedasphaltbindertodeterminethecriticalhightemperatureofthebinderafterRTFOaging(temperatureatwhichG*/sin(δ)is2.2kPa).

5. CalculatethehighPGlimitoftherecoveredreclaimedasphaltbinderbasedonthelowesttemperaturesobtainedinSteps2and4.

6. PerformaDSRtestwith8mmparallelplategeometryontheRTFO-agedrecoveredreclaimedasphaltbindertodeterminethecriticalintermediatetemperature(temperatureatwhichG*xsin(δ)is5,000kPa).

7. Performabendingbeamrheometer(BBR)test(AASHTOT313)ontheRTFO-agedrecoveredreclaimedasphaltbindertodeterminethecriticallowtemperatures

13

(temperatureatwhichcreepstiffness[S]isequalto300MPaandtemperatureatwhichm-valueis0.30).

8. CalculatethelowPGlimitoftherecoveredreclaimedasphaltbinderbasedonthehighest(leastnegative)temperaturesdeterminedinStep7.

3.2.2 BlendedBinderPreparationBlendedasphaltbinderswerepreparedbymixingvirginasphaltbindersandrecoveredRAPbinderatratesof75:25and60:40(representingbinderreplacementratesof25and40percent),andrecoveredRASbinderatarateof85:15(representingabinderreplacementrateof15percent).Thebindersweremixedwithaglassstirreruntilahomogeneousblendwasobtained.Aftermixing,theblendedbinderswereconditionedinanRTFOperAASHTOT240tosimulatetheshort-termagingthatoccursduringasphaltmixproduction.AttemptstoprepareahomogenizedrecoveredRASandvirginbinderblendwereunsuccessful,andthereforeblendedbindertestingwasonlyconductedonblendedextractedRAPandvirginbinders.3.2.3 FrequencySweepTestsTheRTFO-agedblendedbindersweretestedwithaDSRusing8mmparallel-plategeometrywitha2mmplate-to-plategapsettingat4°C,20°C,and40°Catfrequenciesrangingbetween0.1Hzand100Hzateachtemperature.Theamplitudestrainwassetat1.0percenttoensurethebindersbehavedinalinearviscoelasticrange.Themeasuredcomplexshearmodulusvalues(G*)wereusedtoconstructasphaltbindermastercurvesatthereferencetemperature(i.e.,20°C)byfittingthedatatothesigmoidalfunctionshowninEquation3.1.Thetestingfrequenciesatanytestingtemperaturewereconvertedtothereducedfrequencyatthereferencetemperatureusingatime-temperaturesuperpositionprinciple(Equation3.2)withtheaidofanArrheniusshiftfactor(Equation3.3).TheparametersofthesigmoidalfunctionaswellastheactivationenergytermintheArrheniusshiftfactorequationwereestimatedusingtheSolverfeatureinMicrosoftExcel®byminimizingthesumofsquareerrorbetweenpredictedandmeasuredvalues.Examplesofthemeasuredshearmodulusandthecorrespondingmastercurveat20°CforblendedasphaltbindersareshowninFigureandFigure2,respectively.

𝑙𝑜𝑔 𝐺∗(𝑓!) = δ+ !!!!!!!×!"#(!!)

(3.1)where: δ,𝛼,𝛽,𝑎𝑛𝑑 𝛾aresigmoidalfunctionparameters

𝑓! isthereducedfrequencyatreferencetemperature𝑇!.

𝑙𝑜𝑔 𝑓! = 𝑙𝑜𝑔 𝑎! 𝑇 + 𝑙𝑜𝑔( 𝑓) (3.2)where: 𝑓isthetestingfrequencyattestingtemperatureT(ºC)

𝑓! isthereducedfrequencyatreferencetemperature𝑇!(℃)

𝑙𝑜𝑔 𝑎! 𝑇 = !!" !" ×!

(!!− !

!!) (3.3)

where: 𝑎! 𝑇 istheshiftfactorvaluefortemperatureT(ºK)𝐸!isactivationenergyterm(Joules[J]/mol)𝑇! isthereferencetemperatureindegreesKelvin

14

Figure3.1:Exampleofmeasuredshearmodulusofablendedbinderat20°C.

Figure2.2:Exampleofadevelopedmastercurveforablendedasphaltbinderat20°C.

3.3 FineAggregateMatrixTesting

3.3.1 PreliminarySamplePreparationPreliminaryFAMsamplepreparationmethodswerebasedonthosecitedintheliterature(8-10).Mixeswerepreparedwithmaterialpassingthe#4(4.75mm),#8(2.36mm),and#16(1.18mm)sieves.The#4and#8mixesprovidedsatisfactoryquantitiesofFAM;the#16mixesweredifficulttosieveandverylargesamplesneededtobepreparedtoobtainsufficientquantitiesofmixtopreparecompactedspecimens.

15

3.3.2 UCPRCFAMSamplePreparationMethodAfteraseriesoftrialtests,thefollowingprocedurewasdevelopedandadoptedforthepreparationofFAMspecimensfortheUCPRCstudy:

1. Prepareafull-gradedasphaltmixatoptimumbindercontentwithvirginbinderandvirginaggregatesaccordingtoAASHTOR35.

2. Short-termagethelooseasphaltmixfortwohoursatthemixcompactiontemperaturefollowingAASHTOR30.

3. DeterminethetheoreticalmaximumspecificgravityaccordingtoAASHTOT209(RICEtest).

4. Sievethelooseasphaltmixtoobtainapproximately1.5kgofmaterialpassingtheselectedsieve(i.e.,#4,#8,or#16).Whererequired,gentlytampdownthemixtobreakupagglomerations.Mixespassingthe#16sievearenotrecommendedgiventhatlargevolumesofmaterialneedtobepreparedtoobtainsufficientmixtopreparecompactedsamples.

5. Determinethebindercontentofthefinemixbyextractionandrecovery(AASHTOT164).(ExtractionandrecoverywasusedinthisUCPRCstudyasanalternativetoignitionoventesting[AASHTOT308]duetoconcernaboutlosingveryfineaggregateparticlesduringtheignitionprocess).

6. SievetheRAPmaterialtoobtainapproximately1.5kgoftherequiredgradation(i.e.,#4,#8,or#16).

7. DeterminethebindercontentandgradationoffineRAPparticlesbyextractionandrecovery.

8. Determinevirginbinder,virginaggregate,RAP,andRAPaggregatequantitiesforselectedbinderreplacementvaluesbasedonthebindercontentandaggregategradationsdeterminedfromtheextractionandrecoverytests(Step5andStep7).

9. PrepareasphaltmixeswithdifferentpercentagesofRAPbasedontherequiredbinderreplacementrate.

10. DeterminethetheoreticalmaximumgravityoftheFAMmix.11. Short-termagethelooseFAMmixfortwohoursatthemixcompactiontemperature

followingAASHTOR30.12. CompacttheFAMmixinaSuperpavegyratorycompactor(followingAASHTOT312)to

fabricateaspecimenwith150mmdiameterand50mmheightwith10to13percenttargetair-voidcontent.

13. Subjectthespecimentolong-termaging(i.e.,PAV)ifrequiredforthetestingphase.14. Core12.5mmcylindricalFAMspecimensfromthe150mmdiameterspecimen.

Examplesofa150mmcompactedspecimenandcored12.5mmspecimensareshowninFigure.

15. Determinetheair-voidcontentoftheFAMspecimensbyfirstdeterminingthesaturatedsurface-dryspecificgravity(AASHTOT166A)andthencalculatingtheair-voidcontentswiththisandthepreviouslymeasuredtheoreticalspecificgravity(Step10)accordingtoAASHTOT269.TheweighstationusedformeasuringFAMspecimenair-voidcontentisshowninFigure.

16. DrytheFAMspecimensandstoretheminasealedcontainer(Figure)topreventdamageandexcessiveshelf-agingpriortotesting.

16

Figure3.3:FAMspecimenscoredfromaSuperpavegyratory-compactedspecimen.

Figure3.4:Weighstationforair-voidmeasurement(a)andFAMspecimenstorage(b).

Afterpreparationofanumberoftrialmixes,itwasobservedthatthe#4mixeshadlargeaggregatesrelativetothediameterofthe12.5mmcore.Itwasconcludedthatthepresenceoftheselargeraggregatescouldpotentiallyinfluencethetestresultsandintroducevariabilitybetweentestresultswithinthesamemix.Consequentlyallfurthertestingwasrestrictedtomixespreparedwithmaterialpassinga#8(2.36mm)sieve.

17

3.3.3 FineAggregateMatrixMixTestSetupFAMspecimenspreparedaccordingtothemethoddescribedinSection3.3.2weretestedusingasolidtorsionbarfixtureinanAntonPaarMCR302DSR.Thistestingconfigurationisknownasadynamicmechanicalanalyzer(DMA).WhenperformingtestsonFAMspecimens,specialattentionmustbegiventoensuringthatthespecimeniscorrectlyalignedandsecurelyclampedintheDSR.Eachspecimenmustbecarefullyinspectedandcheckedtoensurethatitsedgesarecleanandundamagedintheclampingzone,andthattherearenolocalizedweakareas(e.g.,aggregatestornoutduringcoring)thatcouldinfluencetheresults.Inotherstudies(8-10,30),referenceismadetotheuseofsteelcaps,gluedtobothendsoftheFAMspecimen,tosecurethespecimenintothetestingframe.InitialtestingattheUCPRCcomparedtestswithandwithoutthecaps.ThisapproachwasnotpursuedbasedondiscussionswiththeDSRmanufacturer,whostatedthatthegluezonebetweenthecapandthespecimenwouldlikelyhaveasignificantinfluenceontheresults.InsteadacustomclamprecommendedbytheDSRmanufacturerwasused.FigureshowsthefixedspecimenintheDSR-DMAusedinthisproject.

Figure3.5:DSR-DMAtorsionbarfixtureusedforFAMtesting.

3.3.4 AmplitudeSweepTestsAmplitudesweeptestswereperformedontheFAMspecimenstodeterminethelinearviscoelasticrangeofmaterialbehavior.TheshearmodulusofeachFAMspecimenwasmeasuredat4ºCandafrequencyof10Hzwhentheshearstrainincreasedfrom0.001to0.1percent.AnexampletestresultisshowninFigure.TheshearstiffnessoftheFAMspecimenisindependentoftherateofshearstaininthelinearviscoelasticregion.

18

Figure3.6:ExampleFAMspecimenamplitudesweeptestresults.

3.3.5 FrequencySweepTestsFrequencysweeptestsmeasuredthecomplexshearmodulusinawiderangeoffrequencies(0.1Hzto25Hz)atthreedifferenttemperatures(4°C,20°C,and40°C).Basedontheresultsoftheamplitudesweeptests,frequencysweeptestsatastrainrateof0.002percentwerecompletedtoensurethatthematerialwasinthelinearviscoelasticregion.FAMspecimenshearmodulusmastercurveswereconstructedbasedontime-temperaturesuperpositionprinciplesusingthemeasuredmoduliovertherangeoftemperaturesandfrequencies.ThefunctionsdescribedinSection3.2.3wereusedtoconstructshearmodulusmastercurvesfortheFAMspecimens.Examplesofshearmodulusanddevelopedmastercurvesatthe20°CreferencetemperatureforaFAMmixareshowninFigureandFigure,respectively.

Figure3.7:ExampleofmeasuredshearmodulusofaFAMspecimenat20°C.

19

Figure3.8:ExampleofshearmodulusmastercurveofaFAMspecimenat20°C.

20

4. TestResults

4.1 AsphaltBinderTesting

4.1.1 RAPandRASBinderCharacterizationRepresentativesamplesofreclaimedasphaltpavement(RAP)andreclaimedasphaltshingle(RAS)materialswerecollectedandsenttoacontractinglaboratoryforextractionandrecoveryoftheasphaltbinder.Thebinderwasextractedusingtrichloroethylene(AASHTOT164)andrecoveredusingtheAbsonmethod(ASTMD1856).TheextractedRAPbinderwastestedaccordingtotheNCHRP9-12guidelinesdiscussedinSection3.2.1.TheperformancegradingcriteriaandvaluesoftherecoveredRAPbindersarelistedinTableandsuggestameangradingequatingtoPG88-6.Theresultswereconsideredtobereasonablyrepresentativeofanagedbinder.Itisnotknownwhetherthechemicalsolventsusedintheextractionprocessinfluencedtheresultsinanyway.FurtherresearchisrequiredtoevaluatetheinfluenceofdifferentchemicalsolventsontheextractionandrecoveryofbindersfromRAPmaterials,includingthosecontainingasphaltrubberandpolymer-modifiedbinders.

Table4.1:High,Intermediate,andLowCriticalTemperaturesofRAPBindersCriticalTemperature Parameter MeanTemperature1

(°C)S

(MPa)m

High(Original,DSR)High(RTFO-aged,DSR)Intermediate(RTFO-aged,DSR)

G*/sinδ≥1.00kPaG*/sinδ≥2.20kPa

G*xsinδ≤5,000kPa

92.886.943.9

N/A N/A

Low@0°C(RTFO-aged,BBR)Low@10°C

Testedat0°CTestedat10°C -6.3

310127

0.2620.365

1Meanoftwotests

ThebinderrecoveredfromtheRAScouldnotbetestedaccordingtoAASHTOM320sinceitwasnotsufficientlyworkabletoallowmoldingofthetestspecimensafterthreehoursofheatingat190ºC,asshowninFigure.Thisobservationwasconsistentwithotherstudies,whichreportedmeasuredhighPGlimitsofRASbinderinexcessof120°Candestimatedlimitstobeashighas240°C(34,36).4.1.2 BlendedRAPandVirginBinderCharacterizationAsecondsampleofRAPmaterialwassenttoanexternallaboratoryforbinderextractionandrecovery.Atoluene-ethanolmix(85:15),whichhasbeenshowntohavelessdetrimentaleffectonthechemistryandrheologyofextractedasphaltbinders(31),wasusedasthesolventinthisextraction.TherecoveredRAPbinderwasblendedwiththedifferentvirginbinderstosimulate25percentand40percentbinderreplacement.Apartialfactorialexperimentoftestingwascompletedtoevaluatethepropertiesoftheseblendedbinders(seeTable3.1)asfollows:• Allfivebindersweretestedat25percentbinderreplacement• Twoofthebinders(sampledfromRefinery-A)weretestedat40percentbinder

replacement

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• Oneofthebinders(Refinery-APG64-16)wastestedwitharejuvenatingagentat40percentbinderreplacement

Figure4.1:RecoveredRASbinderafterthreehoursofconditioningat190°C.

Thevirginandblendedbinderswereshort-termagedinanRTFOandthentestedwithaDSR(8mmparallelplatewith2mmgapsetting)tomeasuretheshearmoduliofthebindersatthreetemperatures(4°C,20°C,and40°C)andarangeoffrequencies(0.1to100Hz).ThemastercurveparametersfortheevaluatedbindersareprovidedinTable.

Table4.2:MasterCurveParametersforVirginandBlendedBinders

BinderReplacement

(%)

MixIdentification1 MasterCurveParameters

δ α Β γ Ea(J/mol)

0

PG64APG64BPG64CPG58APG58B

-3-3-3-3-3

4.734.614.894.534.49

1.321.341.291.080.80

0.690.700.780.760.81

191,301194,798191,105181,467167,421

25(RAP)

25%RAP_PG64A25%RAP_PG64B25%RAP_PG64C25%RAP_PG58A25%RAP_PG58B

-3-3-3-3-3

5.045.024.985.085.07

-1.39-1.49-1.75-1.12-1.03

-0.62-0.58-0.69-0.60-0.61

203,802211,663211,792195,467192,711

40(RAP)

40%RAP_PG64A40%RAP_PG64A+RA40%RAP_PG58A

-3-3-3

4.995.055.01

-1.83-1.14-1.52

-0.61-0.67-0.58

217,237198,743208,848

15(RAS)

Nottested

1A,B,andCdenotethesourcerefinery. RA=RejuvenatingagentFigureshowsthemastercurvesofthefivevirginbindersevaluated.ThemoduliofthePG58asphaltbinderswerelowerthanthePG64binders,asexpected.ThethreePG64bindershadsimilarshearmoduli,withonebinder(Refinery-C)beingslightlysofteratlowfrequenciesandstifferathighfrequencies.ThePG58-22binderfromRefinery-BwassofterthantheequivalentbinderfromRefinery-A.

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Figure4.2:Shearmoduliofvirginasphaltbinders(20°C).

Figureshowstheshearmodulusmastercurvesforblendedbinderswith25percentRAPbinderreplacement.AlthoughtheRAPbinderreducedthedifferencesbetweenthemoduliofthefiveasphaltbinders,therankingofthebinderswasstillcontrolledbythepropertiesofthebasebinders.Themastercurvesoftheblendedbindersmergedathighfrequencies(>1,000Hz),regardlessofthebasebindersourceandgrade.Figureshowstheshearmodulusmastercurvesforblendedbinderscontaining40percentRAPbinderreplacement.ThePG64-16basebinderblendwasstifferthanthePG58-22blend,asexpected.Therejuvenatingagentreducedthestiffnessoftheblendedbindertoalevelapproximatelyequaltothatofthevirginbinder.ThemastercurvesoftheblendedbinderwerenormalizedtotheircorrespondingvirginbindermastercurvestomoreeasilycomparetheeffectsofincorporatingRAPintothedifferentvirginasphaltbinders(Figure).Thisanalysisshowedthefollowing:

• Using25percentRAPbinderreplacementincreasedthemodulusofthevirginbinderbyuptoeighttimes,dependingonthebindersource,bindergrade,andtestingfrequency.

• ThestiffnessofthePG58bindersincreasedmorethanthatofthePG64bindersforbindersfromthesamerefinery.

• ThebindersfromRefinery-AwereleastaffectedbytheadditionofRAP.

• Whenusing40percentRAPbinderreplacement,thestiffnessoftheblendedbinderincreasedbyupto13.5timesthatofthevirginbinder.

• Whenrejuvenatingagentwasadded,thenormalizedcurveconfirmedthattheshearmodulusoftheblendedbinderwith40percentRAPbinderreplacementwassimilartothatofthevirginbinderovertherangeoftestingfrequencies.

23

• Increasesintheshearmodulusofblendedbindersmostlyoccurredinthefrequencyrangeof0.00001Hzand0.1Hz.

Figure4.3:Shearmoduliofbinderswith25percentRAPbinderreplacement(20°C).

Figure4.4:Shearmoduliofbinderswith40percentRAPbinderreplacement(20°C).

24

PG64-16(Refinery-A) PG58-22(Refinery-A)

PG64-16(Refinery-B) PG58-22(Refinery-B)

Figure4.5:Comparisonofnormalizedshearmodulimastercurvesforblendedbinders.

25

PG64-16(Refinery-C)

Figure4.5:Comparisonofnormalizedshearmodulimastercurvesforblendedbinders(continued).

26

4.2 FineAggregateMatrixMixTesting

FAMmixspecimenswerepreparedaccordingtotheproceduredescribedinSection3.3.2.Atotalof26FAMmixeswereevaluated.ThebindercontentsoftheRAPandRASweredeterminedtobe7.1and23.7percentrespectively,bytotalweightofthemix,usingtheasphaltbinderextractiontest(AASHTOT164).ThetargetaggregategradationusedwasthesameforalltheFAMmixesregardlessofthebindergradeandRAPorRAScontent,andisshowninFigure.ThegradationandquantityofvirginaggregatewereadjustedaccordingtothequantityandgradationoftheRAPand/orRASinthemixtomeetthetargetFAMgradation.TheFAMmixescontainingRAShadaslightlycoarsergradationthantheFAMmixeswithvirginbinderonlyandwithRAPbinderduetothecoarsergradationoftheRASmaterials.However,thedifferencewasnotsignificantgiventhatonly5.4percentRAS(bytotalweightofmix)wasused.

Figure4.6:GradationofFAM,RAP,andRASmaterials.

4.2.1 FAMSpecimenAir-VoidContentOneofthemainconcernswithregardtotherepeatabilityoftestresultsusingFAMspecimensistherangeofair-voidspermixtype.FigureandFigureshowtheair-voidcontentsmeasuredonthespecimens(fourspecimenspermix).Theair-voidcontentsrangedbetween10.5and12.5percent,whichwaswithinthetargetrangeandconsideredacceptableforthisstudy.Air-voidcontentswereconsideredinalltestresultanalyses.

0.0%

20.0%

40.0%

60.0%

80.0%

100.0%

Perc

ent P

assi

ng

Particle Size (mm)

RAP gradation

RAS gradation

FAM target gradation

0.075 0.1500.3000.6001.1802.360

#200 #100 #50 #30 #16 #8

0.075 0.150 0.300 0.600 1.180 2.360

Sieve Number

27

Figure4.7:FAMspecimenair-voidcontentsforPG64mixes.

Figure4.8:FAMspecimenair-voidcontentsforPG58mixes.

4.2.2 AmplitudeSweepStrainTestResultsThestrainlimitsforlinearviscoelastic(LVE)behavioroftheFAMmixes,determinedfromtheresultsoftheamplitudesweeptest,areshowninFigureandFigure.Thefollowingobservationsweremade:

• TheLVEstrainlimitswereinfluencedbyvirginbindergrade,bindersource,andRAP/RAScontent.TheeffectofbindersourceappearedtohavealesserinfluenceontheresultsofthePG64binderscomparedtothePG58binders.

• TheRAPbinderappearedtomobilizeandblendwiththevirginbinderduringmixing,therebychangingtheviscoelasticpropertiesofthemixasshownbythereductionintheLVEstrainlimit.

28

Figure4.9:FAMspecimenLVErangeformixeswithPG64virginbinders.

Figure4.10:FAMspecimenLVErangeformixeswithPG58virginbinders.

• TheLVEstrainlimitdecreasedwithincreasingRAPcontent,asexpected.Replacing25

and40percentofthevirginbinderwithagedbinderfromtheRAPresultedinabout20to70percentand70to90percentreductionintheLVEstrainlimit,respectively.

• ReductionsinLVEwerealsonotedonthemixescontainingRAS,withthechangeconsistentwiththepercentbinderreplacement(15percent).

• RejuvenatingagenthadanotableinfluenceonthemixescontainingRAP,butonlyamarginalinfluenceonthemixescontainingRAS.ThisimpliesthattheRASbindermightnothavebeeneffectivelymobilizedatthemixproductiontemperaturesusedinthis

29

studyanddidnoteffectivelyblendwiththevirginbinderevenwhenarejuvenatingagentwasadded.Inthiscase,theobservedreductionsinLVEontheRASmixescanprobablybeattributedtotheeffectivelowervirginbindercontent,ratherthantheeffectofthestifferblendedbinder.

4.2.3 FrequencyandTemperatureSweepTestResultsSigmoidalfunctionmastercurveswereconstructedusingthemeasuredshearmodulusatvariouscombinationsoftemperatureandfrequency.Theestimatedparametersofthesigmoidalfunction(Equation3.1)andactivationenergytermintheArrheniusshiftfactor(Equation3.3)fortheFAMmixesareprovidedinTable.

Table4.3:MasterCurveParametersforFAMMixesBinder

Replacement(%)

MixID1 MasterCurveParameters

δ α β γ Ea(J/mol)

0

PG64APG64BPG64CPG58APG58B

00000

3.763.873.633.713.74

-0.96-0.93-1.41-0.79-0.53

-0.52-0.43-0.62-0.52-0.51

164,414174,701172,503162,828158,722

25(RAP)

25%RAP_PG64A25%RAP_PG64B25%RAP_PG64C25%RAP_PG58A25%RAP_PG58B

00000

4.173.994.103.963.99

-1.06-1.19-1.22-1.07-1.19

-0.39-0.38-0.45-0.42-0.38

176,435179,082179,341170,216165,906

40(RAP)

40%RAP_PG64A40%RAP_PG64A+RA40%RAP_PG64B40%RAP_PG64B+RA40%RAP_PG64C40%RAP_PG64C+RA40%RAP_PG58A40%RAP_PG58B

00000000

4.213.844.084.144.603.954.104.29

-1.06-1.03-1.14-0.86-0.94-1.17-1.15-0.85

-0.34-0.46-0.36-0.40-0.35-0.49-0.38-0.36

180,414166,743177,121170,255173,209167,399171,885169,832

15(RAS)

15%RAS_PG64A15%RAS_PG64A+RA15%RAS_PG64B15%RAS_PG64B+RA15%RAS_PG64C15%RAS_PG64C+RA15%RAS_PG58A15%RAS_PG58B

00000000

3.743.803.653.473.773.983.793.82

-0.93-0.70-0.88-0.87-1.18-0.74-0.88-0.65

-0.45-0.48-0.42-0.49-0.53-0.54-0.42-0.44

170,253162,233171,575169,124166,295160,332170,828161,161

1A,B,andCdenotethesourcerefinery. RA=RejuvenatingagentTheshearmodulusmastercurvesfortheFAMmixesdifferentiatedbybinderreplacementrateareshowninFigurethroughFigure,anddifferentiatedbybindersourceareshowninFigurethroughFigure.NormalizedmastercurvesareincludedwiththelattergroupofplotstobetterillustratetheeffectoftheRAPandRAS.ThenormalizedcurveswereobtainedbydividingthemodulioftheFAMmixeswithbinderreplacementbythecorrespondingmoduliofthecontrolmixesateachrespectivefrequency.Thefollowingobservationsweremade:

30

• Thedifferencesinshearmodulusbetweenthedifferentcontrolmixeswereconsistentwiththedifferencesinbindergrade.Minordifferenceswerenotedbetweenthebinderswiththesamegradebutfromdifferentrefineries;thisbeingattributedtotheslightdifferencesbetweentheair-voidcontentsofeachspecimenandpotentiallytothebinder(i.e.,crudeoil)source.MixesproducedwithPG58binderswerelessstiffthanthemixesproducedwithPG64binders,asexpected.

• AddingRAPtothemixincreasedthestiffnessofallthemixesatallfrequencies,asexpected.Themixeswith40percentbinderreplacementwerecorrespondinglystifferthanthosewiththe25percentbinderreplacement,especiallyatthelowertestingfrequencies.Thenormalizedplotsshowthat25percentand40percentbinderreplacementcausedrespectivestiffnessincreasesupto4.5timesand7.5timesthatofthevirginbinder.ThevariationbetweenthedifferentmixesandbindergradeswaslessapparentwhencomparedtothemixeswithoutRAPbinderreplacement.

• AddingRAStothemixesappearedtohavelittleeffectontheshearmodulus,supportingtheconclusioninSection4.2.2thattheRASbinderdidnotfullyblendwiththevirginbinderandthatdifferencesinperformancebetweenthevirginandblendedbindersareattributabletodifferencesintheeffectivebindercontentandtoair-voidcontent(seeFigureandFigure).

• TheshearmodulioftheFAMmixeswithrejuvenatingagentwerelowerthoseofthecorrespondingmixeswithouttherejuvenator,asexpected.TheeffectoftherejuvenatingagentwasmorenoticeableinthemixescontainingRAPthaninthemixescontainingRAS.

4.2.4 AnalysisofVariance(ANOVA)TheANOVAapproachwasusedtostatisticallyidentifythesignificancelevelofinfluentialfactors,whichincludethevirginbindersourceandgrade,percentageofRAPandRASbinderreplacement,anduseofarejuvenatingagent.TheANOVAwasperformedusingthecomplexshearmodulus(G*)valuesat0.001Hz,1.0Hz,and1,000Hzfrequenciesatthereferencetemperatureof20°Casthedependentvariables,andusingbindersource,bindergrade,percentbinderreplacement,anduseoftherejuvenatingagentastheindependentvariables.ThechoiceofG*0.001Hz,G*1Hz,andG*1,000Hzasthedependentvariableseliminatedanypotentialbiascausedbyfrequencyandtemperature.Thenullhypothesisfortheanalysiswasthatthemeanshearmoduluswasthesameforallindependentvariablecategories(i.e.,thesamplemeansofG*0.001Hzwouldbeequalregardlessoftheamountofbinderreplacement).Asignificancelevelof0.01wasusedintheanalysis(i.e.,anyvariablewithap-valuelargerthan0.01wasconsideredtobestatisticallyinsignificant).

31

Figure4.11:MastercurvesofcontrolFAMmixes. Figure4.12:MastercurvesofFAMmixeswith25percentRAP

binderreplacement.

Figure4.13:MastercurvesofFAMmixeswith40percentRAP

binderreplacement.Figure4.14:MastercurvesofFAMmixeswith15percentRAS

binderreplacement.

32

Figure4.15:PG64-16-A:ShearandnormalizedmodulusmastercurvesofFAMmixes.

Figure4.16:PG58-22-A:ShearandnormalizedmodulusmastercurvesofFAMmixes.

33

Figure4.17:PG64-16-B:ShearandnormalizedmodulusmastercurvesofFAMmixes.

Figure4.18:PG58-22-B:ShearandnormalizedmodulusmastercurvesofFAMmixes.

34

Figure4.19:PG64-16-C:ShearandnormalizedmodulusmastercurvesofFAMmixes.

35

TheANOVAresultsarelistedinTable.Basedonthep-valuesforthesignificantvariables,theamountofreclaimedasphaltmaterialusedwasthemostsignificantfactorinfluencingshearmodulusatthethreedefinedtestingfrequencies.Theuseoftherejuvenatingagentwasthenextmostsignificantfactor.AsphaltbindersourceandbindergradehadtheleastinfluenceontheshearmodulusofFAMmixesattheselectedfrequencies.

Table4.4:ANOVAResults

Variable TypeG*0.001Hz G*1Hz G*1,000Hz

F-value p-value F-value p-value F-value p-value

%BinderReplacement

0%25%RAP40%RAP15%RAS

135.789 2.52e-15 121.726 1.63e-14 47.579 1.3e-08

BinderSourceRefinery-ARefinery-BRefinery-C

0.217 0.806 15.859 5.77e-06 9.204 0.000434

BinderGradePG64-16PG64-16PG58-22

2.920 0.064 1.043 0.361 0.174 0.841182

RejuvenatingAgentEffect

NoRAWithRA 91.360 1.68e-12 69.448 9.58e-11 15.319 0.000298

4.2.5 ComparingAsphaltBinderandFAMTestResultsFigurethroughFigureshowtherelationshipbetweentheshearmoduliofasphaltbindersandthecorrespondingshearmodulioftheFAMmixesatfrequenciesof0.1Hz,1.0Hz,and10Hz(atthe20°Creferencetemperature),obtainedfromfrequencysweeptesting.Thesefrequencieswereselectedsinceloadingfrequenciesbeyondthisrangearenottypicalonin-servicepavements.Reasonablecorrelations(r2values)wereobservedbetweentheasphaltbinderstiffnessesandtheFAMmixstiffnessesatthesethreefrequencies.DiscrepanciesbetweenthetwomeasuredstiffnessesmaybeanindicationthatcompleteblendingofthevirginandreclaimedasphaltbinderswasnotachievedintheFAMmix,butwasforcedduringthechemicalextractionandrecovery.Althoughthesepreliminaryresultsappearpromising,onlyalimitednumberoftestswerecompleted,andadditionaltestingwillberequiredbeforefirmconclusionscanbedrawn.

36

Figure4.20:Comparisonofasphaltbinder

andFAMmixshearmodulus(0.1Hzat20°C).Figure4.21:Comparisonofasphaltbinder

andFAMmixshearmodulus(1.0Hzat20°C).

Figure4.22:ComparisonofasphaltbinderandFAMmixshearmodulus(10Hzat20°C).

37

5. ConclusionsandInterimRecommendations

ThisreportsummarizesthemainfindingsfromaprojectfundedbytheNationalCenterforSustainableTransportation(NCST)toinvestigatetheuseofhigherpercentagesofreclaimedasphaltpavement(RAP)andreclaimedasphaltshingles(RAS)asareplacementforapercentageofthevirginbinderinnewasphaltmixesinCalifornia.Theresearchfocusedontestingproceduresthatdonotfirstrequirechemicalextractionandrecoveryoftheage-hardenedasphaltbindersfromtheRAPandRAS.Fivedifferentasphaltbinderscoveringtwoperformancegrades(PG64-16andPG58-22)andsourcedfromthreeCaliforniarefinerieswereevaluatedinthisstudy.TheinfluenceoftwodifferentpercentagesofRAP(25and40percentbybinderreplacement)andonepercentageofRAS(15percentbybinderreplacement)wereevaluatedthroughpartialfactorialasphaltbindertestingandfullfactorialfineaggregatematrix(FAM)mixtesting.Theeffectofapetroleum-basedrejuvenatingagentaddedtoselectedmixes(with40percentRAPand15percentRASbinderreplacement)wasalsoinvestigated.Testingwaslimitedtotheintermediatetemperaturepropertiesofthemixes(i.e.,4°Cto40°C).Keyobservationsandfindingsfromthisprojectincludethefollowing:

• AsphaltbinderextractedandrecoveredfromRAScouldnotbetestedduetoitsveryhighstiffness.TheRASbinderwasnotsufficientlyworkabletomoldsamplesfortestinginadynamicshearrheometer(DSR)orinabendingbeamrheometer(BBR).

• Testingproceduresweredevelopedaspartofthispreliminarytestingphasetomeasuredynamicshearmodulusatdifferenttemperaturesandfrequencies,andamethodforpreparingandtestingFAMspecimenswasdeveloped.Cylindricalspecimens0.5in.(12.5mm)indiametercoredfromaSuperpavegyratory-compactedFAMspecimenweretestedusingatorsionbarfixtureinaDSR.PreliminarytestingofFAMmixespreparedwithmaterialspassingthe#4,#8,or#16(4.75mm,2.36mm,or1.18mm)sievesindicatedthatthisapproachisrepeatableandreproducible,andproducesrepresentativeresultsforcharacterizingtheperformancerelatedpropertiesofcompositebinderatbinderreplacementratesupto40percentandpossiblyhigher.Useofmaterialspassingthe#8sieve(2.36mm)isrecommended.

• TheeffectofRAPinincreasingthestiffnessofblendedbinderswasdependentprimarilyontheasphaltbindergradeand,toalesserextent,bythesourceofasphaltbinder.

• Statisticalanalysesofthetestresultsindicatedthatasphaltbindergradeandsource,RAPandRAScontent,andrejuvenatingagentallhadasignificantinfluenceonFAMmixstiffness,asexpected.

• TheFAMmixescontainingRASshowedsimilarstiffnessestothecorrespondingcontrolmixes(i.e.,containingnoreclaimedmaterials),suggestingthattheRASbinderdidnoteffectivelyblendwiththevirginbinderatthetemperaturesandmixingdurationsusedinthisstudy.

• TheinfluenceofrejuvenatingagentonreducingtheblendedbinderandFAMmixstiffnesseswasevident.Additionaltesting(beyondthescopeofthisstudy)isrequiredto

38

evaluatethelong-termbehaviorofmixesproducedwithrejuvenatingagentstodeterminewhetherthebenefitsarelimitedtoproductionandearlylife,orwhethertheyextendthroughthedesignlifeofthelayer.

• ReasonablecorrelationswereobservedbetweenthestiffnessesofasphaltbinderandthestiffnessesofFAMmixesattestingfrequenciesrangingfrom0.1Hzto10Hz.DiscrepanciesbetweenthetwomeasuredstiffnessesmaybeanindicationthatcompleteblendingofthevirginandreclaimedasphaltbinderswasnotachievedintheFAMmix,butwasforcedduringthechemicalextractionandrecovery.Thiswarrantsfurtherinvestigation.

Basedonthefindingsfromthisstudy,FAMmixtestingisconsideredtobeapotentialappropriateprocedureforevaluatingthepropertiesofblendedasphaltbinderinmixescontainingrelativelyhighquantitiesofRAPandRAS.Furthertestingonawiderrangeofasphaltbindergrades,asphaltbindersources,andRAPandRASsourcesisrecommendedtoconfirmthisconclusionandtodevelopmodelsforrelatingbinderpropertiesdeterminedfromFAMmixtestingtothosedeterminedfromconventionalperformancegradetesting.Chemicalanalysesofblendedbindersmayprovideadditionalinsightsforinterpretingtestresultsandwarrantsfurtherinvestigation.

39

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