evaluation of the combined s of reclaimed asphalt … of reclaimed asphalt pavement (rap), reclaimed...
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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
21
• 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.
22
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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