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CHARACTERIZATIONOFASPHALTBINDEREXTRACTEDFROMRECLAIMEDASPHALT
SHINGLES
ByJ.RichardWillis,Ph.D.
PamelaTurner
January2016
CHARACTERIZATIONOFASPHALTBINDEREXTRACTEDFROMRECLAIMEDASPHALTSHINGLES
By
J.RichardWillis,Ph.D.PamelaTurner
NationalCenterforAsphaltTechnologyAuburnUniversity,Auburn,Alabama
January2016
iii
DISCLAIMER
Thecontentsof this reportreflect theviewsof theauthorswhoareresponsible for the factsandaccuracyofthedatapresentedherein.Thecontentsdonotnecessarilyreflecttheofficialviews or policies of the sponsored agency, the National Center for Asphalt Technology, orAuburn University. This report does not constitute a standard, specification, or regulation.Commentscontainedinthisreportrelatedtospecifictestingequipmentandmaterialsshouldnotbeconsideredanendorsementofanycommercialproductorservice;nosuchendorsementisintendedorimplied.
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1. Report No. NCAT Report 16-01
2. Government Accession No.
3. Recipient's Catalog No.
4. Title and Subtitle CHARACTERIZATION OF ASPHALT BINDER EXTRACTED FROM RECLAIMED ASPHALT SHINGLES
5. Report Date January 2016
6. Performing Organization Code
7. Author(s) J. Richard Willis, Ph.D. and Pamela Turner
8. Performing Organization Report No.
9. Performing Organization Name and Address National Center for Asphalt Technology 277 Technology Parkway Auburn, AL 36849
10. Work Unit No. (TRAIS) 11. Contract or Grant No. G00007328
12. Sponsoring Agency Name and Address Federal Highway Administration 1200 New Jersey Avenue, SE Washington, DC 20590
13. Type of Report and Period Covered Final Report 2013-2015
14. Sponsoring Agency Code
15. Supplementary Notes FHWA Contracting Officer’s Representation: Christopher Wagner
16. Abstract An 80% increase in the amount of RAS used in asphalt mixtures was reported from 2009 to 2012. Despite this increase, there is still little guidance given on the characterization of RAS binder in AASHTO MP 023 and PP 078. In addition to the lack of direction, many contractors and owner agencies do not have equipment capable of determining the actual high and low temperature performance grades of the RAS binder; therefore, work needs to be completed which can aid owner agencies and contractors in determining the true PG grades of RAS binder. While a common virgin binder is PG 64 – 22, RAS binders are much stiffer with critical high temperature grades between 140 and 180°C and critical low temperature grades between 0 and 40°C. If this stiffer binder is not considered in design, it can negatively influence fatigue and thermal cracking performance. The objective of this research is to investigate methods of characterizing RAS asphalt binder for both the critical high and low temperatures. Binder was extracted from RAS and tested to determine the true (or measured) PG grade of the binder. In addition to direct measurement, extrapolation methods were assessed to determine appropriateness in case equipment was not available for direct measurement. Finally, within sample and between sample testing variability was quantified for RAS binders using conventional testing methodology. These tests were completed on RAS samples from across the U.S. and included both post-consumer (PC) and manufacturers’ waste (MW) RAS. Ultimately, it was determined that one could extrapolate the critical high temperature grade of RAS binders ensuring that variability and outliers were considered in the analysis; however, less repeatable and reliable results were discovered when assessing critical low temperatures.
17. Key Words SHINGLE, BINDER, VARAIBILITY, PERFORMANCE GRADE
18. Distribution Statement No restriction. This document is available at www.ncat.us.
19. Security Classif. (of this report) Unclassified
20. Security Classif. (of this page) Unclassified
21. No. of Pages 39
22. Price
Form DOT F 1700.7 (8-72) Reproduction of completed page authorized
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TABLEOFCONTENTSTABLE OF CONTENTS ................................................................................................................ 51 Introduction ................................................................................................................................. 6
1.1 Background ....................................................................................................................... 61.2 Objectives and Scope ........................................................................................................ 7
2 Literature Review ........................................................................................................................ 82.1 RAS Asphalt Binder ....................................................................................................... 10
3 Materials and Test Methods ...................................................................................................... 123.1 Materials ......................................................................................................................... 123.2 Test Methods ................................................................................................................... 12
4 Test Results ............................................................................................................................... 184.1 RAS Binder Critical High Temperature Grade ............................................................... 184.2 RAS Binder Critical Low Temperature Grade ............................................................... 26
5 Conclusions and Recommendations ......................................................................................... 326 References ................................................................................................................................. 33Appendix A High temperature test results ............................................................................... 35Appendix B High temperature Extrapolations ......................................................................... 38
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1 INTRODUCTION 1.1 BackgroundEngineersbeganusingreclaimedasphaltshingles(RAS)inpavementmixturesasanalternateasphaltsourceinthe1980sand1990s(1).WhenpolymermodificationofasphaltbindersbecamemorecommonintheSuperpavePerformanceGrading(PG)specifications,practitionersbegantosearchforwaystoreduceasphaltbindercostwhilestillreceivingthedesiredlevelofperformance.Thisencouragedtheasphaltpavementindustrytouserecycledproductssuchasreclaimedasphaltpavement(RAP),groundtirerubber(GTR),andRASintheirmixtures.WhileproductslikeGTRserveasanasphaltmodifierbyeasingtheindustry’sdependenceonthesupplyofpolymers(suchasstyrene-butadiene-styrene),RAPallowscontractorstoreplacebothaggregateandasphaltbinderwhileRASallowscontractorstoreplaceasphalt(primarily).Agency,industry,andacademiahaveworkeddiligentlyandsuccessfullytosuccessfullyincreaseRAPpercentagesonanationalbasis.SuccessfulRASutilizationisstilldevelopingandistheprimaryreasonforthisreport.Nearly11milliontonsofwasteshinglesareproducedeachyear,resultinginapproximately22millioncubicyardsofwastematerialneedingtobelandfilled(2).Environmentalstandardshaveevolvedsincethe1980s,forcingdisposalsitestoeithercloseorlimittheamountofasphaltshinglestheycanaccept.Between1980and1997,morethan11,000RASdisposalsitesclosed,causingtippingfeestoescalatetonear$100perton(1,3,4).Asphaltshinglesaccountforapproximately8to10percentoftheannualbuilding-relatedwasteandconstructiondebrisproducedintheU.S.annuallyandisthethirdlargestbuildingwastematerialintheworld(5).Inadditiontoreducingthebuildingwaste,usingjustonetonofRAStoreplaceaggregateandasphaltinanewmixturecanreducethecarbonfootprintoftheasphaltpavingindustryby55tonsofcarbon(6)Thus,usingRASinasphaltmixtures,ineffect,reducesboththefiscalandenvironmentalcostsofasphaltpavementbeingproduced.RAShasalsobeenshowntoimprovetheperformanceofasphaltmixturesintermsofrutresistance,stability,andhightemperaturesusceptibility(7);however,theimproperuseofRAS(i.e.eitherusingtoomuch,toocoarseagrind(sizeofshingle),ornotusingsoftPGasphalt)hasbeenshowntocauseprematurefailuresinsomepavements.An80%increaseintheamountofRASusedinasphaltmixtureswasreportedfrom2009to2012(8).Despitethisincrease,thereisstilllittleguidancegivenonthecharacterizationofRASbinderinAASHTOMP023andPP078.Inadditiontothelackofdirection,manycontractorsandowneragenciesdonothaveequipmentcapableofdeterminingtheactualhighandlowtemperatureperformancegradesoftheRASbinder;therefore,workneedstobecompletedwhichcanaidowneragenciesandcontractorsindeterminingthetruePGgradesofRASbinder.WhileacommonvirginbinderisPG64–22,RASbindersaremuchstifferwithcriticalhightemperaturegradesbetween140and180°Candcriticallowtemperaturegradesbetween0
7
and40°C.Ifthisstifferbinderisnotconsideredindesign,itcannegativelyinfluencefatigueandthermalcrackingperformance. 1.2 ObjectivesandScopeTheobjectiveofthisresearchistoinvestigatemethodsofcharacterizingRASasphaltbinderforboththecriticalhighandlowtemperatures.BinderwasextractedfromRASandtestedtodeterminethetrue(ormeasured)PGgradeofthebinder.Inadditiontodirectmeasurement,extrapolationmethodswereassessedtodetermineappropriatenessincaseequipmentwasnotavailablefordirectmeasurement.Finally,withinsampleandbetweensampletestingvariabilitywasquantifiedforRASbindersusingconventionaltestingmethodology.ThesetestswerecompletedonRASsamplesfromacrosstheU.S.andincludedbothpost-consumer(PC)andmanufacturers’waste(MW)RAS.
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2 LITERATUREREVIEWAsphaltroofingmaterialsincludecompositionshingles,built-uproofing,andtorchdownroofing(apolymer-modifiedasphaltmembranestrengthenedwithfabricsandcommonlyusedonflatroofs).Themajorcomponentsofasphaltroofingwasteincludeasphalt,mineralfillerandgranules,glassfibermatting,organicpaperfelt,andnails.Thereareanumberofpotentialendusagesforasphaltroofingwaste,includingasphaltmixtures,whichiscurrentlythelargestmarketforRAS(9).Asphaltshinglescontainatleasttwoproductsneededinasphaltmixtureproduction:asphaltbinderandfinecrushedaggregate.Theyalsoproducefibers(10-20%byweight)thatmaybeusefulincertaintypesofasphaltmixtures.RAScontainsapproximately19to36%asphaltbinderbyweight.Inaddition,thegranulesintheshingles(approximately20-38%byweight)areasourceofaggregateusedinasphaltpavementmixtures.Anumberoflaboratoryandfield-scaleresearchstudieshavebeenconductedtoevaluatetheuseofasphaltshinglesinhotmixasphalt(HMA)andstonematrixasphalt(SMA).Someofthesebenefitsincludethefollowing(10):
• Reduceddemandforvirginasphaltbinderandaggregate,• SignificantreductiontopurchasedMFforSMAmixtures,• Improvedresistancetoruttingduetothereinforcementprovidedbyfiberscontainedin
shingles,and• ReducedproductioncostofHMA.
TheasphaltbinderinRASdecreasesthedemandforvirginasphaltcementandprovidesseveralbenefitstoboththeindustryandstateagencies.First,recycledbinderfromRASreducesthecostoftheasphaltbinderneededdependingonthestateand/orsource.Wastefromshinglefactoriescanbeprocessedandimmediatelybeaddedtothehotmixasphaltprocessorrenewedwithrejuvenatingchemicalspriortothemixprocess.Secondly,asphaltmixturesrequirespecificaggregategradationswithspecificdurabilityproperties.ThemineralorceramicaggregateinRASprovidesasourceoffineaggregateandreducesthedemandforvirginaggregate;however,thisreductionofaggregateissmall.Finally,certainpropertiesofasphaltpavementhavebeenshowntoimprovewiththeadditionofrecycledasphaltshingles.Theseincluderuttingresistance(11).Whilethecompositionofshinglesvariesdependingonthemanufacturerandroofingapplication,mostarecomposedoffourbasicmaterials:asphaltcement,feltorfiber,mineralorceramicaggregate,andmineralfiller.Organicorfiberglassfeltbackingsformthebasicstructureforshingles.Theorganicfeltistypicallycomposedofeithercelluloseorwoodfibersandisdesignedtosupporttheasphaltandaggregategranules.Fiberglassbackingsaremanufacturedbymixingfineglasswithwaterintheformofaglasspulpthatisthenformedintoafiberglasssheet(12,13).Thebackingisthensaturatedwithasphaltcement.
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Shingleasphaltsare“airblown,”whichincreasestheirstiffnesswhenusedinasphaltmixturescomparedtoconventionalpavingasphalt.Theyarefurtherstabilizedwithafiller(70%passingthe#200sieve)(10,14).Asecondapplicationof“airblown”asphaltisappliedasacoveringforbothsidesoftheshingle.Thetopsideoftheshingleisthencoveredwithgranulesdesignedtoprotecttheasphaltfromboththesun’sultravioletraysandphysicaldamageduetoabrasiononrooftops.Mostshinglemanufacturersuseacombinationofcrushedrockscoatedwithceramicmetaloxidesasgranules.Additionalheadlapgranulescanbeusedinthisapplication.Bothaggregategranulesareidealforroofingshinglesduetotheiruniformsize,toughness,andangularshapes(13).Insomecases,chemicalsarealsoaddedtotheaggregatetopreventalgaegrowth(14).Shinglesarefinishedwithadustingoffinesandtothebacksurfacetopreventtheagglomerationoftheshinglesthatcouldoccurduringtransportation.AschematicofthefinalproductisshowninFigure1.Table1presentsestimatesofthepercentageofeachmaterialinorganicandfiberglassshingles.
Figure1Schematicofasphaltshinglecomposition(10).Table1CompositionofShingles(14,15,16)Component OrganicFelt FiberglassMatAsphaltCement 30-36% 19-22%Felt(Fiber) 2-15% 2-15%MineralAggregate 20-38% 20-38%MineralFiller 8-40% 8-40%Justastherearedifferencesbetweenorganicandfiberglassshingles,therearealsodifferencesinthematerialcompositionbasedonshinglesource.LossofaggregateparticlesinthePCshinglesgenerallycauseshigherasphaltcontentthantheMWshingles.ExposuretocontaminantsalsocausesPCshinglestocontainmoredeleteriousmaterialsthanMWshinglessuchaspaper,wood,andnails.Whilemanyofthesecontaminantsareremovedduringthegrindingprocess,furtherremovalofdeleteriousmaterialsmaybenecessarybeforeRAScanbeusedinasphaltmixtures(13).
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AnunderstandingofeachcomponentinRASandhowitcancontributetoanasphaltmixtureisessential.PCshinglestockpilestendtoexhibitmorevariabilitythanMWshinglesinsize,aggregategradation,andasphaltcontentaswellasmaterialpropertiessuchasspecificgravity.Shingletype,manufacturer,andagecansignificantlyinfluencethesefactors(17).Currently,PCRASisusedmorefrequentlythanMWRASbecausethereis10timestheamountofPCshinglesavailableforuse.2.1 RASAsphaltBinderThedesiretouseRASinasphaltmixturesstemsfromtheabilitytosubstantiallyreducetheoverallmaterialcostbyreplacingvirginasphaltbinderwithreclaimedasphaltinapavementmixture.Inorderforthistobecost-effective,theasphaltcontentoftheRASformixtureproportioninganditsperformancegrade(PG)mustbequantifiedtoensuremixtureperformance.SinceRASasphalthavebeenairblown,theyareinherentlystifferthanvirginormodifiedasphaltsandhavedifferentrheologicalproperties.Thisstiffnesscausesmanystateagenciestobeconcernedaboutlong-termdurabilityofmixturescontainingRASinrelationshiptocrackingandstripping.(3,18,19).Oneexampleofthiswasseenatthe2012NCATTestTrack,intestsectionsdesignedfortheFloridaDepartmentofTransportation.TwocomparativesectionsweredesignedusingPG76-22basebinders.Thefirstsectionhad20percentRAPwithoutanyRAS,andthesecondsectioncontained20percentRAPwithanadditional5percentRAS.ThesectionwhichincludedRAShadsignificantlymorelowseveritytop-downcrackingthantheRAPonlysection(20).ThemostcommontoolforassessingasphaltbinderstodayisAASHTOM320,StandardSpecificationforPerformanceGradeBinderGrading.ManystatesdonotrequiretheRASbindertobeperformancegradedduetothedifficultyinhandlingandtesting.Inordertousehighershingleorbinderreplacements,AASHTOPP78,DesignConsiderationsWhenUsingReclaimedAsphaltShingles(RAS)inAsphaltMixtures,requiresuserstoknowthePGoftheRASbindertocompleteblendingchartsusedtodeterminethecorrectvirginbindergradetobeusedinthemixdesign.Despitepotentialhandlingandtestingdifficulties,itisimportantthatblendedRASasphaltandvirginbindermeetsthesameperformancecriterionasvirginbinderintermsofbindergrade,strength,anddurability(21).ThePerformanceGradeofRASbindersisdeterminedusingAASHTOM320onmaterialsthathavebeenextractedusingmethodspreviouslymentionedandthenrecoveredusingASTMD5404.Inthecurrentperformancegradingsystem,thestiffnessandelasticitypropertiesoftheasphaltbinderareevaluatedatthreeaginglevels.First,theoriginal,unagedbinderisassessed.Second,theasphaltbinderundergoesasimulatedshort-termagingintherollingthinfilmoven(RTFO)beforebeingassessedagain.Thefinalassessmentoccursafterasimulatedlong-termaginginthepressureagingvessel(PAV).CurrentmixdesignandbindergradingspecificationsdonotrequireRAPbinderstoundergolong-termagingsincetheyhavealreadybeenagedinthefield,buttheydoundergoshort-termaging.
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WhilethisprovisionisgivenforRAPbinders,nosuchguidanceisprovidedforRASbinders.Itisknownthatairblowingduringshingleproductionincreasesthebinderviscosity.ThebinderofPCshinglesisfurtheragedwhiletheshingleisactingasaroofingmaterial.Still,researchershavepresentedresultsusingboththeRTFOandPAVagingprocedures(21).AgencieshavereporteddifficultyworkingwithrecoveredRASbindersduetotheirextremestiffnessatnormalbinderhandlingtemperaturesandthesmallmoldshapesrequiredforsomebindertesting(21).Additionally,commonDSRmodelsusingwaterbathsfortemperaturecontrolcannotbeusedtodirectlyassessthehightemperaturegradeoftheRASbindersincemanyRASbindershavecriticalhightemperaturesabovetheboilingpointofwater(18).Inmanycases,RASbindersalsoaredifficulttotestforcriticallowtemperatures,asthebindersmustproceedbelow-36°Ctoreachthecriticallowtemperaturestiffnessbuthavem-valuesthatwillonlypassattemperaturesgreaterthan0°C(18).ThisdifferenceinlowtemperaturefailurevaluesindicatesthatrecoveredRASbindersareextremelybrittle,makingthecreationoftestspecimensforlowtemperaturetestingdifficult.AgencieshavereportedusingcheesegraterstoshredRASbindersoitcouldbePGgraded(22).ExampleperformancegradesofshinglebindersarepresentedinTable2toshowthedifficultiesandextremecriticaltemperaturesdeterminedwhenassessingRASbinders.Whilethislistofbindergradesisnotexhaustive,onecommonlyseesthatPCRASbinderismuchstifferthanMWRASbinderwhenreviewinglowPGgradesfortheRAS.Table2RASPGGradesReference Location RASType HighPG LowPG23 Oregon MW 134 NA18 Wisconsin MW 124-154 0>22 Missouri MW 143+ 0>24 Minnesota MW 134-153.9 (-12.7)to(-6.1)24 Minnesota PC 121.2–133.1 (-6.9)to(10.6)NCAT Alabama PC 175.4 41.7NCAT Alabama MW 132.6–137.2 (-18.6)to(-13.0)
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3 MATERIALSANDTESTMETHODS3.1 MaterialsSixRASsampleswereobtainedtoevaluatethehightemperatureperformanceofRASbinder,andfourweresuppliedforlowtemperatureevaluation(Table3).ThesesamplesweresenttoNCATfromcontractorswhovolunteeredtoprovidematerial.Someofthesampleswerenotlargeenoughtoconductthefullsuiteoftesting;therefore,thesampleswereeitherusedforhightemperatureorlowtemperaturetesting.TheresearchteamtriedtoreceivesamplesfromdifferentgeographicregionsofthecountrythatcommonlyuseRASaswellassamplesfrombothPCandWMshingletypes.ThesameofRASfromOregonwasablendofbothPCandMWRASinsteadofjustasingleRASsource.Table3RASSamples
State ShingleType TemperatureTestingMW PC High Low
Michigan ü ü ü ü
Oregon ü ü ü üNewHampshire ü ü ü
Georgia ü ü Texas ü ü ü
Wisconsin ü ü3.2 TestMethods 3.2.1 ExtractionandRecovery AsphaltbinderwasextractedandrecoveredfromeachRASsourceusingthecentrifugeextractionmethod(ASTMD2172-05MethodA)withTrichloroethylene(TCE)asthesolvent.Othersolventsareusedbyotheragencies,andtheAsphaltInstituteiscurrentlyconductingsomeworktocomparetheeffectsofusingdifferentsolventsonRASbindertestingresults.SomestatesdonotuseTCEasasolventbecauseofthelimitedavailabilityandenvironmentalconcernsassociatedwithitsuse.Therotaryevaporatorrecoveryprocedure(ASTMD5404-03)wasusedtoremovethesolventfromtheextractedbinder.DuetothehighviscosityoftherecoveredRASbinder,itwasnecessarytoincreasethedraintimeandtemperatureusedforremovingtherecoveredbinderfromtherecoveryflask.Forthistesting,atotaldraintimeof30minutesatatemperatureofapproximately190°CwasusedwhichmightcauseRASstiffeningatthispointoftesting.Threeextraction/recoveryprocedureswereperformedforeachRASsourcewiththerecoveredbindersfromeachprocedurebeingstoredinseparatecontainersforhightemperaturetesting.Afourthextraction/recoveryprocedurewasperformedforeachRASsourcetoobtainrecoveredbinderforlowtemperaturetesting.
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3.2.2 BinderTestingMethodsTherecoveredRASbindersweretestedinaccordancewiththeproceduresdescribedinAASHTOM320-10,AASHTOR29-08,andAASHTOD7643-10todeterminehighandlowperformancegradesandcontinuousgradingtemperatures.TruegradingtemperaturesasdescribedinASTMD7643-10aredefinedasthetemperatureatwhichatestcriterionismet(forexample,thecontinuousgradingtemperatureforRTFO-agedmaterialtestedintheDSRisthetemperatureatwhichG*/sin(δ)=2.20kPa)andareusuallydeterminedbyinterpolatingbetweenapassingandfailingtestresult.ThereisnoofficialguidancegivenregardingagingofrecoveredbindersexceptforAASHTOM323-13,AppendixX1,StandardSpecificationforSuperpaveVolumetricMixDesign,whichstatesthattherecoveredbinderfromRAPshouldonlybeshort-termagedintheRollingThinFilmOven(RTFO)priortotesting.AnattemptatagingrecoveredRASbinderintheRTFOshowedthattheviscosityoftheRASbinderwastoohighandthatitdidnotmoveinthebottlesduringtheprocedure.Therefore,theRASbindersforthisstudyweretestedintheiras-recoveredstatewithnoadditionalaging.ShorttermandlongtermagingofRASbindersintheRTFOorPAVisconsideredredundantduetothepreviousagingofinservicePCshinglesandtheagingduetotheairblownprocessofallshingles.Thesemanufacturingandin-situagingconditionsaremoreseverethantheRTFOandPAV.ThehightemperaturepropertiesoftheRASbindersweremeasuredasdescribedinAASHTOT315-08usingaTAInstrumentsAR2000EXmodelDynamicShearRheometer(DSR).ThisDSRmodelhasthecapabilityoftestingattemperaturesupto150°Cusingaheatedupperplateassembly.Fortemperatureshigherthan150°C,anenvironmentaltemperaturechamberassemblywithaliquidnitrogenpurgewasused.TheDSRprocedureisperformedusinga25-mmdiameterparallelplategeometrywitha1000micronsamplegap.Asinusoidalshearloadisappliedtothetestspecimenatafrequencyof10rad/secandatargetangularstrainlevelof10%todeterminecomplexshearmodulus(G*)andphaseangle(δ).Forcriteriapurposes,therecoveredRASbinderwastestedasRTFO-agedmaterial,eventhoughnoagingwasperformed.ThetemperaturesnecessarytoachieveafailinghightemperatureresultforrecoveredRASbindertypicallyexceedthetemperaturerangeofmanyDSRmodels.Thisresultsintheneedtoextrapolateby50–60°Cormoretodeterminethecontinuousgradingtemperature.Toaddresstheissueofextrapolationoversuchawidetemperaturerangeanditseffectoncontinuousgradedetermination,twomethodswereusedtocalculatethehighcontinuousgradingtemperatureoftheRASbinders.Onesetofsamplesfromeachindividualextractionwastestedat82,88,and94°C,thehigheststandardtesttemperaturesthatawatercontrolledDSRshouldbeabletomaintain.TheresultingvaluesofG*/sin(δ)wereplottedversustemperatureonalogscaleandextrapolatedtoavalueof2.20kPa.ThesecondsetofsampleswastestedatelevatedtemperaturescorrespondingtopassingandfailingvaluesofG*/sin(δ)andthecontinuousgradingtemperaturecalculatedbyinterpolatingbetweenthetworesultsusingtheequationsprovidedinASTMD7643-10.
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LowcontinuousgradingtemperaturesweredeterminedfortherecoveredRASbinderusingtwotestprocedures.TheBendingBeamRheometer(BBR)procedureasdescribedinAASHTOT313-12measureslowtemperaturestiffnessandrelaxationpropertiesusingthinbeamsofasphaltbindertowhicha980mNcreeploadisappliedfor240seconds.Thestiffnessparameter,S(t),iscalculatedbasedonthemeasureddeflectionofthebeamduringtheloadingperiod.Therelaxationparameter,m(t),iscalculatedastheslopeoftheS(t)curveattimet.ContinuousgradingtemperaturesforlowtemperaturetestingaredefinedasthetemperaturesatwhichS(60sec)=300Mpaandm(60sec)=0.300,withthewarmerofthetwotemperatureschosenasthecontinuousgrade.TestingrecoveredRASbinderintheBBRpresentedsomechallengesthatmadeitdifficulttoobtainreliableresults.ThehighviscosityoftherecoveredRASbinderincombinationwiththesmalldimensionsoftheBBRsamplemold(6.35-mmx12.70-mmx127-mm)madepreparingtestspecimensdifficult,asthebinderdidnotflowintothemoldsevenly.TheRASbindertendedtocoolandstiffenbeforereachingthebottomofthemold,leavinggapsinthetestspecimen.Inadditiontothedifficultywithpreparingthetestspecimens,thebehavioroftherecoveredRASbinderatthetesttemperaturestypicallyusedintheBBR(below0°C)prohibitedtestingattemperaturesthatbracketthelowtemperaturepass/failcriteria.Atlowtemperatures,recoveredRASbinderhasverypoorrelaxationpropertiesandtypicallyfailsthem(60sec)criteriaatthewarmesttemperaturethattheBBRbathcanreliablymaintain(+6°C).Thelowtemperaturestiffnessvaluesrequiretestingatmuchcoldertemperaturesthanwhatthem(60sec)requirestoachieveafailingtestresultbasedontheS(60sec)criteria.ThepoorrelaxationpropertiesoftheRASbindersmakethetestspecimensbrittleatcoldertemperaturesandpronetobreakagewhenthetestloadisapplied.Sincethem-valueisthecontrollingcriteriaforRASbinders(itscontinuousgradetemperatureishigherthanthecontinuousgradetemperatureforthestiffnesscriteriaandisusedtodeterminethelowPGgradeofthebinder),testingwasperformedatthetwowarmeststandardtesttemperaturespossible:+6and0°C.ThetestresultswerethenextrapolatedtovaluesofS(60)=300Mpaandm(60)=0.300todeterminethelowcontinuousgradingtemperaturesbasedontheBBRcriteria.ThelowcontinuousgradingtemperaturesoftherecoveredRASbindersweredeterminedusingaproceduredevelopedbyWesternResearchInstitute(WRI).The4-mmplateDSRprocedureprovidesamethodforestimatingBBRS(t)andm(t)valuesthateliminatestheneedtomoldtestspecimensandallowsfortestingatwarmertemperaturesthancanbeachievedintheBBRbath.Theprocedureuses4-mmdiameterDSRtestspecimentodeterminevaluesofstoragemodulus(G’(t))overarangeoffrequenciesfrom0.1–100rad/secat0.1%angularstrain(chosentobewithinthelinearregionforthebindersbeingtested).Thefrequencysweepswereperformedattwotemperatures(4and14°Cforthisresearch)andtheresultingisothermswereshiftedusingtheChristensen-Andersonmodeltocreateamastercurveatachosenreferencetemperature.Oncethemastercurvewascreated,G’(t)andtheslopeofthecurveat60seconds,mg’,werecalculatedbyfittingaquadraticpolynomialfunctiontothemastercurve.Equations1and2(developedbyWRI)werethenusedtoconverttheDSRdatatoBBRresultsatthereferencetemperature(25).
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S(t)=21.380+1.718*G’(t (1)m=-0.115*+0.708*mg’ (2)ThecalculationswererepeatedatmultiplereferencetemperaturesandtheresultingS(60)andm(60)valueswereusedtodeterminethelowcontinuousgradingtemperaturesoftherecoveredRASbinders.3.2.3 TestingVariabilityAnalysis ForeachRASsource,threetypesofvariabilitywereconsidered:
• Withinsample–howrepeatablearetestresultsobtainedfrommultipletestspecimentakenfromthesameextraction/recoveryprocedure,
• Betweensample–howreproduciblearetestresultsobtainedfromtestspecimenofthesameRASbindertakenfromdifferentextraction/recoveryprocedures,and
• Testorcalculationmethod–howdodifferentmethodsofdeterminingthesamecriteriaaffectthetestresults.
Table4showsasampletestingmatrixforoneRASbindersource.Table4SampleTestingMatrix
HighTemperature LowTemperature
Extraction Measured Extrapolated BBR 4-mm1 Test1 Test1 Test1 Test1
Test2 Test2 Test2 Test2Test3 Test3 Test3 Test3
2 Test1 Test1 Test1 Test1
Test2 Test2 Test2 Test2Test3 Test3 Test3 Test3
3 Test1 Test1 Test1 Test1
Test2 Test2 Test2 Test2 Test3 Test3 Test3 Test3
EachcellinTable4representsthreereplicatetestresultstoallowfordeterminationofwithinsamplevariability.StatisticalanalysiswasperformedonthereplicateresultsfromeachtestproceduretodeterminewhetherornottheresultsobtainedfromasinglesampleofRASbinderwererepeatable.Iftheresultswerenotrepeatable,thiscouldimplythateithertheRASbinderitselfwasnotahomogenousmaterialorthatitwassensitivetosomeportionofthehandlingortestingprocedures.
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BetweensamplevariabilityforthehightemperaturetestswasevaluatedbyrepeatingthetestproceduresonthreeseparatesamplesofthesamerecoveredRASbinder.Thiswasdonetoevaluateiftheextraction/recoveryprocedurecouldproducerecoveredRASbinderthathadconsistent,reproducibletestresults.Duetotimeandsamplequantitylimitations,betweensamplevariabilityatcoldtemperatureswasnotevaluated.Statisticalcomparisonswerealsoperformedtodeterminetheeffectofthedifferentmethodsofdetermininghighandlowcontinuousgradetemperatures.Forthehightemperatureresults,acomparisonwasmadebetweenthecontinuousgradetemperaturesdeterminedbyextrapolationandthoseobtainedbytestingatpassingandfailingtemperatures.Forthelowtemperatureresults,acomparisonwasmadebetweentheBBRcontinuousgradingtemperaturesandthoseobtainedfromthe4-mmDSRprocedure.3.2.4 HighTemperaturePredictionThetemperaturesnecessarytoachieveafailinghightemperatureresultforRASbindersfrequentlyexceedthetemperaturerangeofsomeDSRmodels,particularlythosethatuseawaterbathfortemperaturecontrol.Becauseofthis,itisoftennecessarytoextrapolateby50–60°Cormoretodeterminethecontinuousgradingtemperature.TwomethodswereusedtocalculatethehighcontinuousgradingtemperatureoftheRASbinders,andtheresultswerecomparedtodeterminewhateffect,ifany,thedifferenceintestprocedurehadonthecontinuousgradetemperatureresults.
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Figure2ExtrapolatedHighContinuousGradeExtrapolationThesecondsetofsampleswastestedatelevatedtemperaturescorrespondingtopassingandfailingvaluesofG*/sin(δ)andthecontinuousgradingtemperaturecalculatedbyinterpolatingbetweenthetworesults.
1.0
10.0
100.0
1000.0
60.0 80.0 100.0 120.0 140.0 160.0
G*/sinδ
,kPa
Temperature,°C
4-extrapolated
2.20
18
4 TESTRESULTSSevenRASsamplesweredeliveredtoNCATforevaluation.Thischapterdescribestheevaluationofthosesamplesforbothcriticalhighandlowtemperatures.4.1 RASBinderCriticalHighTemperatureGrade 4.1.1 DeterminingCriticalHighTemperatureGradeandVariabilityThecriticalhightemperaturegradeofsixRASsampleswasdeterminedusingthepreviouslydescribedmethodology.ThreeofthesamplestestedwerePCRASwhiletwosampleswerefromMWRASstockpiles.ThefinalsamplewasablendofPCandMWRASusedinOregon.OncetheRASbinderhadbeenextracted,thecriticalhightemperaturegradeofeachRASsamplewasdeterminedonthreereplicatesfromthreeseparateextractionsforeachsample.ThisresultedinnineindividualtestpointsforeachRASsample.Table5providesthemeasuredtestresultsfromeachRASsample.IndividualtestresultsaregivenintheAppendixA.Itshouldbenotedthatthesetestresultsandconclusionsarebasedonlimitedtestresultsusingverychallengingtestingprocedures.Whencomparingthevariabilityofthehightemperaturetestresults,Table5showsthatasexpected,thewithinextractionvariabilitywaslowerthanthevariabilityoftheentiredataset.Eightofthe18extractionshadcoefficientsofvariation(COV)lessthan1%,whilesixhadCOVslessthan2%.WhencomparingthecoefficientsofvariationfortheentiredatasetofasingularRASsource,theCOVsrangedfrom3.2to7.7%.Thestandarddeviationsweresimilar.Tenoftheextractionshadstandarddeviationsoftriplicatemeasurementslessthan2°C.Sixextractionshadstandarddeviationsgreaterthan4°C.Thesinglelargeststandarddeviationforasingleextractionwas11.7°C.However,whencomparingthestandarddeviationsofthreereplicatesforthreeextractions,thedataweremorevariable.Standarddeviationsrangedfrom4.6to12°C. ThestatisticsshowthatMWRASwascommonlylessvariablethanPCRAS;however,theonesamplewiththeleastvariabilitybetweenextractionswastheMW/PCRASblendfromOregon.Whentryingtoestablish95%confidenceintervalsforthestandarddeviationsofthewithinextractionandbetweenextractiondatasets,Figures3and4showthatwhilethebetweendatasetisnormalbytheAnderson-DarlingNormalityTest(p=0.328),thewithinextractionstandarddeviationsarenotnormal.Whentransposedonalogscale(Figure5),however,thedatabecomesnormal,andonecanascertaina95percentconfidenceinterval.Therefore,usingthesetwo95percentconfidenceintervals,onemightexpectthestandarddeviationforthetestingofRASbinderbetweentwodifferentsamplestobe4.4and10.3°C.TheexpectedrangefortestingthehightemperaturegradeofRASbinderwithinsingleextractionswouldbe0.9to2.4°C.
19
Table5HighTemperatureTestResults
State Michigan Texas Oregon MichiganNew
Hampshire Georgia
Source MW MWMW/PCBlend PC PC PC
Extract1
Average 135.4 126.6 143.8 160 159.8 148.2StandardDeviation 2 0.2 1.2 1.7 3.7 2.8CoefficientofVariation 1.5 0.2 0.9 1 2.3 1.9
Extract2
Average 133.1 137.4 146 161.7 163.8 151.1StandardDeviation 2.1 3.1 1 0.4 2.2 0.8CoefficientofVariation 1.6 2.3 0.7 0.2 1.3 0.6
Extract3
Average 144.7 131.7 151.9 144.4 145.4 170.3StandardDeviation 0.5 1.8 5.6 0.8 0.6 11.7CoefficientofVariation 0.4 1.4 3.7 0.6 0.4 6.8
Setof9Tests
Average 137.7 131.9 147.2 155.4 156.3 156.5StandardDeviation 5.5 5 4.6 8.3 8.7 12CoefficientofVariation 4 3.8 3.2 5.4 5.6 7.7
20
Figure3BetweenExtractionStandardDeviationNormalityTestResults
Figure4WithinExtractionStandardDeviationNormalityResults
1stQuartile 4.9000Median 6.90003rdQuartile 9.5250Maximum 12.0000
4.3502 10.3498
4.7429 10.8214
1.7843 7.0108
A-Squared 0.35P-Value 0.328
Mean 7.3500StDev 2.8585Variance 8.1710Skewness 0.818897Kurtosis -0.262603N 6
Minimum 4.6000
Anderson-Darling NormalityTest
95% ConfidenceIntervalforMean
95% ConfidenceIntervalforMedian
95% ConfidenceIntervalforStDev
121086
Median
Mean
10864
95%ConfidenceIntervals
SummaryReportforBetween
1stQuartile 0.7500Median 1.75003rdQuartile 2.8750Maximum 11.7000
0.9994 3.6895
0.8000 2.4892
2.0296 4.0548
A-Squared 1.79P-Value < 0.005
Mean 2.3444StDev 2.7047Variance 7.3156Skewness 2.72845Kurtosis 8.68264N 18
Minimum 0.2000
Anderson-Darling NormalityTest
95% ConfidenceIntervalforMean
95% ConfidenceIntervalforMedian
95% ConfidenceIntervalforStDev
121086420
Median
Mean
4.03.53.02.52.01.51.0
95%ConfidenceIntervals
SummaryReportforWithin
21
Figure5Log(within)StandardDeviationNormalityTests4.1.2 ExtrapolatingCriticalHighTemperatureGradeAsshownintheprevioustables,allsixRASsourceshadcriticalhightemperaturegradesgreaterthan100°C.DSRsusingwater-controlledtemperaturebathscannotachievereliabletemperaturesfortestinggreaterthanapproximately94°Cbeforeproblemssuchaswaterboilingbegintooccur.Therefore,inorderforagenciesandcontractorsusingwater-controlledtemperaturebathstodeterminecriticalhightemperaturegradesofRASbinder,anextrapolationmethodologyneedstobedetermined.ThesimplestmethodofextrapolatingthesedatawouldbetousealinearmodeltoplotG*/sinδat82,88,and94°C,andthencalculatethetemperaturewherethedatameetthecriticalhightemperaturecriterion.Thismethodologyisdescribedpreviouslyinmoredetail.Table6providestheextrapolatedhightemperatureresultsforallthreereplicatetestsofeachextraction.AppendixBshowstheindividualtestresults.
1stQuartile -0.12814Median 0.242863rdQuartile 0.45821Maximum 1.06819
-0.04664 0.38442
-0.09691 0.39291
0.32523 0.64975
A-Squared 0.14P-Value 0.972
Mean 0.16889StDev 0.43341Variance 0.18785Skewness 0.008242Kurtosis 0.103291N 18
Minimum -0.69897
Anderson-Darling NormalityTest
95% ConfidenceIntervalforMean
95% ConfidenceIntervalforMedian
95% ConfidenceIntervalforStDev
0.80.4-0.0-0.4
Median
Mean
0.40.30.20.10.0-0.1
95%ConfidenceIntervals
SummaryReportforLog (within)
22
Table6HighTemperatureExtrapolations
State Michigan Texas Oregon MichiganNew
Hampshire Georgia
Source MW MWMW/PCBlend PC PC PC
Extract1
Average 136.3 137.2 145.5 150.9 141.3 137.2StandardDeviation 6.2 0.9 6.5 23.5 25.4 0.9CoefficientofVariation 4.55 0.6 4.5 15.6 17.9 0.6
Extract2
Average 131.1 137.5 139.3 192.0 146.1 137.5StandardDeviation 2.8 1.8 0.6 43.1 1.7 1.8CoefficientofVariation 2.15 1.3 0.5 22.4 1.2 1.3
Extract3
Average 131.1 198.5 148.1 160.5 147.2 198.5StandardDeviation 2.2 53.1 1.1 23.8 4.0 53.1CoefficientofVariation 1.50 26.8 0.7 14.9 2.7 26.8
Setof9Tests
Average 132.9 157.7 144.3 167.8 144.9 157.7StandardDeviation 4.4 40.5 5.1 33 13.1 40.5CoefficientofVariation 3.29 25.68 3.56 19.68 9.08 25.68
ItisnoteworthythatwhenconsideringwithinextractionCOV,fiveoftheRASsampleshadCOVsfortwoextractionsatlessthan3percent,whilethethirdRASextractionhadasignificantlylargerCOV.InmostcaseswheretheCOVwassignificantlylarger,onlyonetestresultcausedtheskewinthedata.TheonlyRASsamplethathadwithinextractionCOVsconsistentlygreaterthan14percentwastheMichiganPCRASwheretherewereconsistentdifferencesbetweenallthreeextrapolations.Whileoneshouldconsidervariabilityintheextrapolations,oneultimatelyneedstoknowiftheextrapolationsareaccuratecomparedtogivenmeasureddata.Tostatisticallyassessthesedata,pairedt-tests(α=0.05)wereusedvalidatethenullhypothesisofnodifferencebetweenthemeasuredandextrapolatedcriticalhightemperatures.ThistestwasconductedontheninetestresultsforeachRASsampleaswellastheentirepopulationoftests.P-valesarepresentedinTable7andshownostatisticaldifferencesbetweenthemeasuredandextrapolateddataforanyofthesixsamplesaswellastheentirepopulation.ThesepreliminaryresultswerebasedononlysixdifferentRASsamples.AdditionaltestingistakingplaceaspartofNationalCooperativeHighwayResearchProject9-55todetermineifthesetrendscontinuebeforemoredefinitiveconclusionsaredrawn.
23
Table7StatisticalAnalysisofExtrapolatedtoMeasuredCriticalHighTemperaturesSample Michigan
MWMichiganPC
OregonBlend
NewHampshirePC
GeorgiaPC
TexasMW
Population
p-value 0.078 0.194 0.178 0.077 0.906 0.095 0.766Despitethelackofevidenceshowingstatisticaldifferences,scatterplotscomparingthemeasuredtoextrapolatedhightemperaturesshowdisagreementbetweenthemeasuredandextrapolateddata(Figure6).Furtherevidenceisgivenbythehistogramofthedifferencesbetweenthemeasuredandextrapolateddata(Figure7).Thoughmanyoftheresultsarewithinafewdegreesofeachother,numerousresultsstillshowerrorsintheextrapolationofmorethan15°Conapointtopointbasisshowingthatsinglereplicateextrapolationcanleadtoerrorincriticalhightemperatureexpectations.
Figure6DifferencesbetweenMeasuredandExtrapolatedData
24
Figure7HistogramofMeasuredMinusExtrapolatedCriticalHighTemperatureBetteragreementisfoundwhencomparingtheaveragesoftriplicatetestingonasingleextraction.Thescatterplot(Figure8)showsthatmuchofthevariabilityseenfromindividualtestingisremoved,andthemajorityofthetestresultsaremorecomparablebetweenthedatasets.However,whenassessingthehistogramofthedifferences(Figure9),sixoftheeighteendatacomparisonshavedifferencesgreaterthan10°C,showingthatfurthertestingmayberequiredtoremovevariabilityfromtheanalysis.Someofthistestingiscurrentlyunderway.Thestatisticalanalysesmaybeslightlyskewedbythelimitedtestresults.
75604530150-15-30
25
20
15
10
5
0
Measured- Extrapolated,C
Freq
uenc
yH istogramofDifferences
25
Figure8ComparisonofMeasuredandExtrapolatedDataofTriplicateTesting
Figure9HistogramofDifferencesbetweenMeasuredandExtrapolatedCriticalHighTemperatureAverageofTriplicateTestingfromSingleExtraction
20100-10-20-30
6
5
4
3
2
1
0
Measured- ExtrapolatedAveragefromTriplicateTesting,C
Freq
uenc
y
26
Similarresultsareseenwhencomparingtheaveragesoftriplicatedatafromthreeseparateextractions.Approximately1/3ofthevarianceshavedifferencesgreaterthan10°C.Therefore,usingtheresultsofthisstudy,oneshouldextrapolatedatainordertoascertainacriticalhightemperaturegradeforRASbinder,runningtriplicatetestsfromasingleextractionandremovingobviousoutlierswouldbethemostappropriatemethod.Theslighterrorsfromtheextrapolatedresultswouldhavelittleeffectonchoosingavirginbinder.TheRASbindershaveacriticalhightemparound120Cto180°C.Thisismuchhotterthanapavementwillseeinitslife.Thecriticaltemperatureisimportantbecauseitwillaffectthefinalblendedbindercriticalhighandlowtemps. 4.2 RASBinderCriticalLowTemperatureGrade ThetwolowtemperaturetestingmethodsdescribedinthemethodologywereusedtodeterminecriticallowtemperaturesforfourRASsources(TexasMW,WisconsinMW,OregonBlend,andNewHampshirePC).ThepurposeofthisportionofthetestingwastodetermineiftheDSRmethodcouldgivecriticallowtemperaturescomparabletothoseobtainedfromtheBBRmethod.Asecondaryreasonforthetestingwastodetermineifonemethodcouldprovidebetterrepeatabilitythantheother.OnlyoneextractionprocedurewasperformedforeachRASsourceduetomaterialandtimelimitations.Usingtherecoveredbinder,threereplicatetestswereperformedforboththeBBRtestandthe4-mmdiameterDSRtest.TheresultsfromeachofthesetestswereusedtocalculatecriticallowtemperaturesbasedontheS(60)andm(60)criteria.ThisresultedinadatasetoftwelvecriticallowtemperaturesforeachRASsource(threepertest/criteriacombination).Itshouldbenotedthatthesetestresultsandconclusionsarebasedonlimitedtestresultsusingverychallengingtestingprocedures. 4.2.1 DeterminingCriticalLowTemperatureGradeUsingBendingBeamRheometerTables8and9showtheBBRS(60)andm(60)criticallowtemperaturesforeachRASsource.Ascanbeseenfromthetables,theresultsbasedontheBBRtestfollowtypicalcriticallowtemperaturetrendsfortheMWRASsourceswiththevaluescalculatedusingtheBBRm(60)criteriabeingwarmerthanthevaluescalculatedusingtheBBRS(60)criteria.TheOregonBlendedRASalsofollowedthistrendfortwoofthethreereplicates,whilethePCRASonlyfolloweditforoneofthethreereplicates.
27
Table8CriticalLowTemperaturesBasedonBBRS(60)CriteriaReplicate TXMW WIMW ORBlend NHPC1 -67.7 -31.5 -36.7 -42.62 -39.4 -26.0 -33.0 -72.23 -35.1 -32.8 -25.7 -26.0Average -47.4 -30.1 -31.8 -46.9StandardDeviation 17.7 3.6 5.6 23.4COV,% 37.3 12.1 17.6 49.9Table9CriticalLowTemperaturesBasedonBBRm(60)CriteriaReplicate TXMW WIMW ORBlend NHPC1 -3.3 2.5 -28.9 -118.02 -9.3 -3.5 -44.5 -64.03 -9.1 -2.3 21.3 14.3Average -7.2 -1.1 -17.3 -55.9StandardDeviation 3.4 3.2 34.4 66.5COV,% 46.7 293.4 198.3 119.0BothsetsofBBRcriticallowtemperatureshadhighvariabilitywithCOVvaluesrangingfrom12.1-293%.AlthoughtheCOVvaluesfortheBBRS(60)resultsappearedtobelowerthantheCOVvaluesfortheBBRm(60)results,apairedt-testanalysis(α=0.05)showedthattherewasnostatisticaldifferencebetweenthevariabilityforthetwocriteria(p=0.087).Inthisanalysisthem(60)andS(60)criteriawerepairedfromasingularRASsource.Standarddeviationsrangedfrom3.6-23.4°CfortheBBRS(60)criticallowtemperaturesand3.2-66.5°CfortheBBRm(60)criticallowtemperatures.Apairedt-testanalysis(α=0.05)showedthattherewasnostatisticaldifferencebetweenthestandarddeviationsforthetwosetsofdata(p=0.401).ThisanalysiswascompletedsimilarlytothepreviouslymentionedCOVanalyses.4.2.1 DeterminingCriticalLowTemperatureGradeUsingDynamicShearRheometerTables10and11showtheS(60)andm(60)criticallowtemperaturescalculatedusingthetestresultsfromthe4-mmdiameterplateDSRprocedure.TheDSRcriticallowtemperaturesalsofollowedtypicaltrendswiththeDSRm(60)criteriahavingwarmercriticaltemperaturesthanthosecalculatedusingtheDSRS(60)criteriaforallfourRASsources.COVvaluesfortheDSRcriticallowtemperaturesrangedfrom40-163.7%fortheDSRS(60)resultsandfrom32.7-147.7%fortheDSRm(60)results.Standarddeviationsforbothcriteriawerehigh,rangingfrom25.1°C-70.4°CfortheDSRS(60)criticallowtemperaturesandfrom10.5°C-35.8°CfortheDSRm(60)criticallowtemperatures.Pairedt-testanalysis(α=0.05)showednostatisticaldifference
28
ineitherCOVorstandarddeviationbetweenthetwocriteria(COVp-value=0.927,Standarddeviationp-value=0.133).Table10CriticalLowTemperaturesBasedonDSRS(60)CriteriaReplicate TXMW WIMW ORBlend NHPC1 -58.9 -12.0 -61.5 -74.72 -87.4 -11.6 -102.3 -26.83 -132.7 -55.3 34.8 -18.8Average -93.0 -26.3 -43.0 -40.1StandardDeviation 37.2 25.1 70.4 30.2COV,% 40.0 95.5 163.7 75.4Table11CriticalLowTemperaturesBasedonDSRm(60)CriteriaReplicate TXMW WIMW ORBlend NHPC1 -25.8 -14.0 -32.9 -50.02 -31.0 5.0 -68.6 -7.93 -47.6 -12.4 2.9 -12.3Average -34.8 -7.1 -32.9 -23.4StandardDeviation 11.4 10.5 35.8 23.1COV,% 32.7 147.7 108.8 98.94.2.3ComparisonofBBRandDSRCriticalLowTemperatureResultsTostatisticallycomparethecriticallowtemperaturesresultsobtainedfromtheBBRtothoseobtainedusingtheDSR,pairedt-tests(α=0.05)wereusedwiththenullhypothesisofnodifferencebetweenthecriticallowtemperaturevalues.SeparateanalysesweredonecomparingtheS(60)andm(60)criticallowtemperaturesforeachRASsample.Acomparisonforeachcriterionwasalsocompletedusingtheentirepopulationoftests.P-valesarepresentedinTables12and13.Table12StatisticalAnalysisofBBRS(60)toDSRS(60)CriticalLowTemperaturesSample TexasMW WisconsinMW OregonBlend NewHampshirePC Populationp-value 0.128 0.820 0.809 0.774 0.425Table13StatisticalAnalysisofBBRm(60)toDSRm(60)CriticalLowTemperaturesSample TexasMW WisconsinMW OregonBlend NewHampshirePC Populationp-value 0.016 0.396 0.617 0.469 0.752TheresultsshownostatisticaldifferencescouldbefoundbetweenthemeasuredandextrapolatedresultsforalmostalltheRASsamplesaswellastheentirepopulation.Theonlyexceptionwasthem(60)criticallowtemperaturesfortheTexasMWRASsource.
29
Despitethelackofevidenceshowingstatisticaldifferences,scatterplotscomparingtheBBRtoDSRcriticallowtemperaturesshowalackofcorrelationbetweenthetwomethodsforeithercriteria(Figures10-13).Furtherevidenceofthislackofagreementisgivenbythehistogramofthedifferencesbetweentheresults.Thoughsomeresultsarewithinafewdegreesofeachother,mostresultsshowdifferencesbetweenthetestmethodsofmorethan25°Conapointtopointbasiswhichwouldmakethesedifferencesbeconsideredpracticalinnature.ThisindicatesthatthereisnotgoodagreementbetweentheDSRandBBRmethodsfortheseRASsamples.DuetothecomplexnatureRASbinders,itisdifficulttodeterminewhichtestresultprovidesthemostaccuratetestresult.
Figure 10 Comparison of BBR S(60) and DSR S(60)
y=0.4679x-32.333R²=0.02432
-160.0
-120.0
-80.0
-40.0
0.0
40.0
80.0
-160.0 -120.0 -80.0 -40.0 0.0 40.0 80.0
DSRS(60)Low
Cric
calTem
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BBRS(60)LowCriccalTemperature,°C
30
1007550250-25-50
3.0
2.5
2.0
1.5
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0.5
0.0
BBR S(60) - DSR S(60)
Freq
uenc
yHistogram of S(60) Differences
Figure11HistogramofS(60)Differences
Figure12ComparisonofBBRm(60)andDSRm(60)
y=0.3033x-18.366R²=0.27715
-160.0
-120.0
-80.0
-40.0
0.0
40.0
80.0
-160.0 -120.0 -80.0 -40.0 0.0 40.0 80.0DSRm(60)Low
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31
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BBR m(60) - DSR m(60)
Freq
uenc
yHistogram of m(60) Differences
Figure13ComparisonofBBRm(60)andDSRm(60)Pairedt-testanalyses(α=0.05)wereusedtoevaluatetheCOVvaluesandthestandarddeviationbetweenthetwotestmethods.TheDSRandBBRtestmethodswerefoundtohavestatisticallythesameCOVvalues(p=0.971)andstandarddeviations(p=0.315).Basedontheseresults,itwouldappearthatthe4-mmDSRtest,whilesimplertorunmaynotprovidecriticallowtemperaturesthatareequivalenttothoseobtainedfromtheBBRprocedureforthissetofRASsamples.TheDSRprocedurealsodoesnotappeartoprovidemorerepeatableresultsthantheBBRprocedure.
32
5 CONCLUSIONSANDRECOMMENDATIONS BasedonthelimitedstudywhichevaluatedvarioustestingandextrapolationmethodsfordeterminingRASbinderproperties,thefollowingconclusionsweredrawn:
• WithinsamplecriticalhightemperaturegradeswerelessvariablethanbetweensamplecriticalhightemperaturegradesforagivenRASsource.Onewouldexpecttheresultsofthreecriticalhightemperaturestovarybetween0.9and2.4°CforagivenRASsource.Thestandarddeviationsforbetweensampletestsrangedfrom4.6to12°C.
• Linearlyextrapolatedcriticalbinderhightemperaturegradeswerestatisticallythesameastestedresults;however,scatterplotsshowedpracticaldifferenceswereevidentwithinthedataset.Usingaveragesoftriplicatetestresultsreducedvariabilityanddisagreement.
• BothDSRandBBRlowtemperaturetestingprovidedvariableandinconsistentcriticallowtemperaturesforRASbinder.
Basedontheseconclusions,thefollowingrecommendationscanbemade:
• OnecanextrapolatecriticalhightemperaturesofRASbinder;however,careshouldbetakentoreducevariability.Removeoutliersandtakeatleastanaverageoftriplicateresultstoensuremorepreciseandaccurateresults.
• BoththeBBRandDSRarevariableandprovideresultswhichmaynotbeaccurateforascertainingthecriticallowtemperaturegradeofRASbinder.Additionalworkneedstobecompletedonthissubject.AnewtestingmethodmaybeneededfordeterminingthelowtemperaturepropertiesofRASbinder.
• OthermethodsshouldbeconsideredforextrapolationofcriticalhighandlowtemperaturegradesforRASbinders.Currently,theAsphaltInstituteisworkingondevelopingandquantifyingthevariabilityofotherextrapolation/blendingmethodsusingthesamematerialsusedinthisstudy.
33
6 REFERENCES
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March2010,AccessedMarch12,2012.4. Bauman,A.“AsphaltShingleRecyclinginMassachusetts,”greenGoatFactSheet,2005.5. BioCycle.“AnalyzingWhat’sRecyclableinC&DDebris,”p.53,2003.6. Caulfield, M. “Asphalt Shingles in Paving,” SolidWaste Association of North America
Meeting,2010.7. C&DRecyclingProgram.“AsphaltRoofingShinglesinAsphaltPavement,”2005.8. Hansen, K. and A. Copeland. Annual Asphalt Pavement Industry Survey on Recycled
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APPENDIXA HIGHTEMPERATURETESTRESULTSTableA-1MichiganMWRASMeasuredCriticalHighTemperatureGradeReplicate MeasuredCriticalHighTemperature,°C
Extraction1 Extraction2 Extraction31 137.6 130.7 144.32 133.8 133.8 144.53 134.7 134.7 145.3Average 135.4 133.1 144.7StandardDeviation 2.0 2.1 0.5COV,% 1.5 1.6 0.4AverageofNineTests 137.7StandardDeviationofNineTests 5.5COVofNineTests,% 4.0TableA-2MichiganPCRASMeasuredCriticalHighTemperatureGradeReplicate MeasuredCriticalHighTemperature,°C
Extraction1 Extraction2 Extraction31 161.6 161.8 144.12 158.3 162.0 145.33 160.2 161.3 143.7Average 160.0 161.7 144.4StandardDeviation 1.7 0.4 0.8COV,% 1.0 0.2 0.6AverageofNineTests 155.4StandardDeviationofNineTests 8.3COVofNineTests,% 5.4TableA-3OregonRASBlendMeasuredCriticalHighTemperatureGradeReplicate MeasuredCriticalHighTemperature,°C
Extraction1 Extraction2 Extraction31 142.4 144.9 145.62 144.3 146.2 156.43 144.7 146.9 153.6Average 143.8 146.0 151.9StandardDeviation 1.2 1.0 5.6COV,% 0.9 0.7 3.7AverageofNineTests 147.2StandardDeviationofNineTests 4.6COVofNineTests,% 3.2
36
TableA-4NewHampshirePCRASMeasuredCriticalHighTemperatureGradeReplicate MeasuredCriticalHighTemperature,°C
Extraction1 Extraction2 Extraction31 164.1 166.1 145.62 158.1 161.9 144.73 157.3 163.4 145.8Average 159.8 163.8 145.4StandardDeviation 3.7 2.2 0.6COV,% 2.3 1.3 0.4AverageofNineTests 156.3StandardDeviationofNineTests 8.7COVofNineTests,% 5.6TableA-5GeorgiaPCRASMeasuredCriticalHighTemperatureGradeReplicate MeasuredCriticalHighTemperature,°C
Extraction1 Extraction2 Extraction31 151.5 152.0 161.92 146.6 150.3 165.43 146.6 150.9 183.7Average 148.2 151.1 170.3StandardDeviation 2.8 0.8 11.7COV,% 1.9 0.6 6.8AverageofNineTests 156.5StandardDeviationofNineTests 12.0COVofNineTests,% 7.7
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TableA-6TexasMWRASMeasuredCriticalHighTemperatureGradeReplicate MeasuredCriticalHighTemperature,°C
Extraction1 Extraction2 Extraction31 126.7 133.9 133.82 126.4 138.4 131.03 126.8 139.9 130.4Average 126.6 137.4 131.7StandardDeviation 0.2 3.1 1.8COV,% 0.2 2.3 1.4AverageofNineTests 131.9StandardDeviationofNineTests 5.0COVofNineTests,% 3.8
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APPENDIXB HIGHTEMPERATUREEXTRAPOLATIONSTableB1MichiganMWRASExtrapolatedCriticalHighTemperatureGradeReplicate MeasuredCriticalHighTemperature,°C
Extraction1 Extraction2 Extraction31 142.7 128.9 130.12 136.0 130.2 130.33 130.3 134.3 131.3Average 136.3 131.1 131.1StandardDeviation 6.2 2.8 2.2COV,% 4.55 2.15 1.50AverageofNineTests 132.9StandardDeviationofNineTests 4.4COVofNineTests,% 3.29TableB2MichiganPCRASExtrapolatedCriticalHighTemperatureGradeReplicate MeasuredCriticalHighTemperature,°C
Extraction1 Extraction2 Extraction31 150.3 162.4 136.62 127.7 241.4 160.83 174.8 172.1 184.3Average 150.9 192.0 160.5StandardDeviation 23.5 43.1 23.8COV,% 15.6 22.4 14.9AverageofNineTests 167.8StandardDeviationofNineTests 33.0COVofNineTests,% 19.68TableB3OregonBlendedRASExtrapolatedCriticalHighTemperatureGradeReplicate MeasuredCriticalHighTemperature,°C
Extraction1 Extraction2 Extraction31 152.8 140.0 147.12 140.2 138.8 147.93 143.6 139.0 149.2Average 145.5 139.3 148.1StandardDeviation 6.5 0.6 1.1COV,% 4.5 0.5 0.7AverageofNineTests 144.3StandardDeviationofNineTests 5.1COVofNineTests,% 3.56
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TableB4NewHampshirePCRASExtrapolatedCriticalHighTemperatureGradeReplicate MeasuredCriticalHighTemperature,°C
Extraction1 Extraction2 Extraction31 126.6 147.0 144.52 170.6 144.1 145.43 126.7 147.1 151.8Average 141.3 146.1 147.2StandardDeviation 25.4 1.7 4.0COV,% 17.9 1.2 2.7AverageofNineTests 144.9StandardDeviationofNineTests 13.1COVofNineTests,% 9.08TableB5GeorgiaPCRASExtrapolatedCriticalHighTemperatureGradeReplicate MeasuredCriticalHighTemperature,°C
Extraction1 Extraction2 Extraction31 138.3 136.9 150.52 136.6 136.0 189.43 136.8 139.5 255.6Average 137.2 137.5 198.5StandardDeviation 0.9 1.8 53.1COV,% 0.6 1.3 26.8AverageofNineTests 157.7StandardDeviationofNineTests 40.5COVofNineTests,% 25.68TableB6TexasMWRASExtrapolatedCriticalHighTemperatureGradeReplicate MeasuredCriticalHighTemperature,°C
Extraction1 Extraction2 Extraction31 138.3 136.9 150.52 136.6 136.0 189.43 136.8 139.5 255.6Average 137.2 137.5 198.5StandardDeviation 0.9 1.8 53.1COV,% 0.6 1.3 26.8AverageofNineTests 157.7StandardDeviationofNineTests 40.5COVofNineTests,% 25.68