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NCATReport17-01

EVALUATIONOFLABORATORYFRICTIONPERFORMANCEOFAGGREGATESFORHIGH

FRICTIONSURFACETREATMENTS

ByMichaelHeitzman

JasonMoore

January2017

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EvaluationofLaboratoryFrictionPerformanceofAggregatesforHighFrictionSurfaceTreatments

NCATReport17-01by

MichaelHeitzman,PhD,PE(WA,IA)

AssistantDirectorPrincipalInvestigator

JasonMoore

LaboratoryManager

NationalCenterforAsphaltTechnologyatAuburnUniversityAuburn,Alabama

January2017

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ACKNOWLEDGEMENTSThisstudywassponsoredbytheMichiganDepartmentofTransportationunderthedirectionofPaulSchiefer,RegionBridgeSupportUnit.TheauthorswouldliketoacknowledgetheeffortsoftheNCATstaffwhoperformedlaboratorytesting.Thestudycouldnotbeaccomplishedwithoutthecontributionsofmaterialsfromthefollowingcompanies.

E-BONDEpoxies,Inc,FtLauderdale,FLRedFlintGroup,EauClaire,WIFlintRockProducts,Commerce,OKFXMinerals,Newell,WVC-EMinerals,Andersonville,GAFairmountMinerals,Chardon,OHWashingtonRock,Graham,WAUSSilica,Mauricetown,NJEarthworksSolutions,Gillette,WY

DISCLAIMER

Thecontentsofthisreportreflecttheviewsoftheauthorswhoareresponsibleforthefactsandaccuracyofthedatapresentedherein.ThecontentsdonotnecessarilyreflecttheofficialviewsorpoliciesoftheMichiganDepartmentofTransportation,theNationalCenterforAsphaltTechnologyorAuburnUniversity.Thisreportdoesnotconstituteastandard,specification,orregulation.Commentscontainedinthispaperrelatedtospecifictestingequipmentandmaterialsshouldnotbeconsideredanendorsementofanycommercialproductorservice;nosuchendorsementisintendedorimplied.

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TABLEOFCONTENTS

LISTOFTABLES........................................................................................................................v

LISTOFFIGURES......................................................................................................................v

LISTOFABBREVIATIONS.........................................................................................................vi

INTRODUCTION/BACKGROUND..............................................................................................1

SCOPEOFSTUDY....................................................................................................................3

TESTPROCEDURE...................................................................................................................4SamplePreparation............................................................................................................4TestProtocol......................................................................................................................4TestResults........................................................................................................................6TestQualityControl............................................................................................................6DataAnalysis......................................................................................................................8

CONCLUSIONSANDRECOMMENDATIONS.............................................................................11

REFERENCES..........................................................................................................................12

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LISTOFTABLES

Table1StudyAggregateTypesandSources.................................................................................4Table2SummaryofDFTResults...................................................................................................7Table3SummaryofCTMResults..................................................................................................7

LISTOFFIGURES

Figure1NCATThreeWheelPolishingDevice...............................................................................2Figure2GenericAsphaltSurfaceFrictionPerformanceCurve.....................................................3Figure3SlabReplicateDFTComparison.......................................................................................8Figure4ComparisonofLaboratoryFrictionPerformance............................................................9Figure5ComparisonofLaboratorySurfaceTexturePerformance...............................................9Figure6CorrelationofFrictionandSurfaceMacrotexture........................................................10Figure7CorrelationofLaboratoryandFieldTerminalFrictionValues(7).................................11

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LISTOFABBREVIATIONS

AASHTO.....................AmericanAssociationofStateHighwayandTransportationOfficialsASTM.........................AmericanSocietyforTestingandMaterialsCTM...........................circulartexturemeterDFT............................dynamicfrictiontesterDFT(40)......................dynamicfrictionmeasuredat40km/hDOT............................DepartmentofTransportationFHWA........................FederalHighwayAdministrationFn...............................frictionnumberHFST..........................highfrictionsurfacetreatmentK................................thousandkm/h..........................kilometersperhourlb................................poundsMDOT........................MichiganDepartmentofTransportationMTD...........................meantexturedepthNCAT..........................NationalCenterforAsphaltTechnologypsi..............................poundspersquareinchrpm............................revolutionsperminuteSN40R........................skidnumberat40mphwithribbedtireTWPD.........................threewheelpolishingdevice

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INTRODUCTION/BACKGROUND

PavementfrictionisonecomponentoftheFederalHighwayAdministration’s(FHWA)RoadwayDepartureSafetyProgramandoneofthetoolsishighfrictionsurfacetreatments(HFST).AnHFSTisanimportantapplicationforcriticalsafetylocationslikebridgedecks,horizontalcurves,andhighspeeddecelerationramps.HFSTusebeganintheearly1950’sintheUSAasathinpolymer-bondedbridgedecktreatment.Theindustrythatinstalledthisproductformanyyearsusedavarietyofaggregatesthattheyfeltperformedwell.TheuseofcalcinedbauxiteastheHFSTaggregatewasfirstpublishedin1976.Atthispoint,theFHWAandAmericanAssociationofStateHighwayandTransportationOfficials(AASHTO)viewHFSTasaspecializedsubsetofthin-bondedpolymeroverlaysforlocationswithcriticalfrictiondemand.Thequestionthatcontinuestobeexaminedistheuseofotherregionallyavailableandlessexpensivefrictionaggregatesthatcanprovidesatisfactoryperformanceasathin-bondedpolymeroverlay.

WhilethisconceptwasbeingsuccessfullyusedinothercountriesforcrashreductionandsimilarproductswerebeingusedintheUSAonbridges,theFHWAOfficeofPavementTechnologyinitiatedtheSurfaceEnhancementsatHorizontalCurvesprogramtodemonstratetheapplicationofHFSTinroadwaycurves.Whenthedemonstrationprogrambegan,AASHTOhadnotwrittentheguidespecificationforHFSTandcompaniesthatbidthedemonstrationprojectsoftenbidtheirthinpolymer-bondedbridgedecktreatmentsystems,whichdidnotalwaysincludecalcinedbauxite.

FHWA,AASHTO,andtheAmericanTrafficSafetyServicesAssociation(ATSSA)havedevelopedanHFSTguidespecification(PP79-14StandardPracticeforHighFrictionSurfaceTreatmentforAsphaltandConcretePavements).Currently,theguidespecificationonlyrecognizescalcinedbauxiteaggregate(1,2).Therefore,theAASHTOdefinitionforHFSTrequirescalcinedbauxite.

TheMichiganDepartmentofTransportation(MDOT)hasspecialprovision12SP-800A-03forHFST,anditspecifiestheuseofcalcinedbauxite(3).TheDepartment’sspecialprovision12SP-712B-01forthinepoxypolymerbridgedeckoverlayspecifiesaggregatepropertiesandincludesalistofsixapprovedsuppliers(4).

Comparativefieldfrictiontestingofalternativeaggregatesforthinpolymer-bondedbridgedecktreatmentsystemsisnotpractical.Theidealtestsiterequiresasinglelocationandthelengthofeachtestsectionmustaccommodateconsistentlockedwheelskidtrailertestinganduniformtrafficabrasion.Thereareveryfewsitesthatwouldmeetthesecomparativetestingcriteria.Ifmultiplesitesareneeded,itisdifficulttofindsiteswithsimilartraffic,climate,andwintermaintenance.

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TheNationalCenterforAsphaltTechnology(NCAT)ThreeWheelPolishingDevice(TWPD),asshowninFigure1,offersapracticalandtechnicallysoundcontrolledevaluationofalternativefrictionaggregates.Thelabevaluationisnotatruefieldtrafficexaminationofperformance,butthemethodpermitsadirectcomparisonofalternativeaggregatesbyapplyinguniformlycontrolledconditioningandtesting.

Figure1NCATThreeWheelPolishingDevice

Figure2depictsagenericpavementfrictionperformancecurveforanasphaltpavement.Theearlyportionoffrictionperformanceexhibitsadramaticincreaseinfrictionastheasphaltbinderfilmwearsoffthepavementsurfacefollowedbyasteepfrictionlossduetoinitialaggregatepolishing.Aftertheinitialaggregatepolishing,thesurfacefrictionperformancestabilizesasdefinedbylong-termfrictionlosstrend,commonlycalledterminalfriction.Whenathinepoxypolymersurfaceisplacedonanexistingpavementorbridgedeck,thereisnoasphaltfilmonthenewsurface,sothesurfacebeginswithitspeakfrictionvalue.Thisstudyfocusedonthelong-termfrictionlosstrend(terminalfriction)ofeachaggregate.

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Figure2GenericAsphaltSurfaceFrictionPerformanceCurve

SCOPEOFSTUDY

Forthepurposesofthisstudy,thetermsbauxiteandHFSTareusedgenericallyanddonotfullyagreewiththerecentlyadoptedAASHTOstandardpractice(PP79-14)discussedintheIntroduction.Whilethetermbauxitereferstoanaturalaggregatewithrelativelysoftproperties,inthisreport,calcinedbauxitewillbesimplyreferredtoasbauxite.Inthisreport,thetermHFSTwillbeusedtodescribetheplacementofathinpolymer-bondedfrictionaggregatesurfacetreatmenttoimprovethefrictionpropertiesofthepavementsurface.Assuch,thetermHFSTdoesnotmeetallthecriteriaofPP79-14.

ThisstudywasadirectcomparisonofelevenaggregatesappliedasHFSTusinganNCATlaboratoryevaluationprocess.TheuseoftheTWPDforsurfacefrictioncomparisonsinthelaboratoryisananalysisprocessthatisstilldeveloping.Sincetherearenospecifiedstandardsorthresholdsforfrictionvalues,thistestprocedureallowsengineersandresearcherstomakerelativecomparisonsoffrictionperformancebetweensurfaces.Itwillbetheresponsibilityofgoverningagenciestodeterminewhatanacceptablethresholdshouldbe.

ThescopeofthelaboratorystudywastoprovideMDOTwithfrictionperformancedatafordeterminingwhichaggregatesourcesmettheagency’scriteriaforHFST.Theobjectivewastoevaluatethefrictionperformanceofelevenaggregatesusingidenticalconditioning(polishing)withtheNCATTWPD.ThedescriptionandsourceoftheaggregatesaregiveninTable1.Testingeachaggregateforspecificationcompliancewasnotapartofthestudy.Eachaggregatesample,asreceived,wasexpectedtomeetthinepoxypolymerbridgedeckoverlaycriteria.

MeasurementVariation

TemperatureImpactVariation

Frictio

n

CumulativeTraffic

Long-termFrictionLossTrend

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Table1StudyAggregateTypesandSources

AggregateName/AggregateType

Location Supplier Supplier’sOfficeLocation

Basalt EauClaire,WI RedFlintGroup EauClaire,WICopperSlag EauClaire,WI RedFlintGroup EauClaire,WIFlint65-8 Picher,OK FlintRockProducts Commerce,OKRKBauxite6x14Ccalcinedbauxite Newell,WV FXMinerals Newell,WV47-4x20calcinedkaolin Roswell,GA C-EMinerals Andersonville,GA60-4x20calcinedkaolin Roswell,GA C-EMinerals Andersonville,GA70-4x20calcinedkaolin Roswell,GA C-EMinerals Andersonville,GABestSand612quartz Chardon,OH FairmountMinerals Chardon,OHArmorStonequartz KingCreekPitOrting,WA WashingtonRock Graham,WAEP5-Modquartz Frederick,MD USSilica Mauricetown,NJTractionControlFeldsparmineral Gillette,WY EarthworksSolutions Gillette,WY

TESTPROCEDURE

SamplePreparation

The11HFSTaggregateswereplacedon20x20inchasphalttestslabs.Tworeplicateslabsweremadeforeachaggregate.Theasphaltsurfacesofthe22slabswerecleanedusingalightsand-blastspraytoremovethesurfaceasphaltfilm.Toensureagoodbondbetweentheaggregateandepoxy,eachaggregatesamplewaswashedtoremovedustandovendried.Theepoxybondingagent,E-BOND526,wasappliedtothesurfaceofeachslabatanapproximaterateof0.04gal/sqftandspreaduniformlywithanotched-toothtrowel.Theaggregatewasbroadcastedbyhandontotheuncuredepoxysurface.Aftertheepoxycuredfor24hours,thesurfacewasswepttoremovelooseaggregate,aggressivelyrubbedwithawoodenboardtodislodgelooselyboundaggregate,andsweptagain.

TestProtocol

ThelaboratoryprotocolfortheNCATTWPDisadevelopingprocedure.TheNCATTWPDwasinitiallydevelopedatNCATina2004-2006study(5).Asecondstudycompletedin2010refined

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thetestparametersandfoundareasonablecorrelationbetweenlaboratoryresultsandfieldtests(6).TheTWPDisdesignedtouniformlycondition(polish)a284mmdiameterpathonthesurfaceofatestslab.

TheconditionedpathistestedbyASTMtestmethodsE2157(StandardTestMethodforMeasuringPavementMacrotexturePropertiesUsingtheCircularTrackMeter)andE1911(StandardTestMethodforMeasuringPavedSurfaceFrictionalPropertiesUsingtheDynamicFrictionTester),commonlycalledthecirculartexturemeter(CTM)anddynamicfrictiontester(DFT),respectively.TheCTMandDFTareusedformeasuringthesurfacetextureandfrictionofpavementsurfaces.Bothtestmethodscanbeusedinthelaboratoryorinthefield.TheCTMmeasuresthepavementsurfacemacrotextureprofileandprovidesameanprofiledepth(MPD)inmillimeterstoquantifythemacrotexture.TheDFTmeasurespavementsurfacefrictionpropertiesasafunctionofspeed(20,40,and60km/hforthisstudy)andprovidesadimensionlessvaluecalledthefrictionnumber(Fn).ThereisnoconsistenttrendthathigherDFTspeedmeasureshigherfriction,sothespeedthatproducesthemostrepeatablemeasure,40km/h,wasusedfortheentirestudy.Inthisreport,theDFTfrictionvaluesarecommonlyexpressedasDFT(40),meaningtheFnat40km/h.Forbothtestprocedures,increasingvaluesindicatehighersurfacefrictioncharacteristics.

FortheevaluationofHFSTaggregatesinthislaboratorystudy,thefollowingtestprotocolwasused.

• ThetworeplicateslabsofeachHFSTaggregateweredividedforconditioningonseparateTWPDunits.

• AnewsetofthreeTWPDtireswasinstalledforeachslabtested.TheTWPDwasoperatedat60rpm,50psitirepressure,and91lbgrosscarriageweight.PreviousstudiesusingtheTWPDshowedthat80,000to100,000(80Kto100K)conditioningcycleswereneededtoreachaterminalsurfacefrictioncondition.Thisstudyextendedthepolishingto140Kcyclestohelpdistinguishperformancebetweenthehigherqualityaggregates.

• EachCTMtestincludedthreereplicatemeasurementsonthedryslabsurface.Atemplatewasplacedovertheslabtoensurethemeasurementsweretakenatthesamelocation.

• EachDFTtestincludedthreereplicatemeasurements.Atemplatewasplacedovertheslabtoensurethemeasurementsweretakenatthesamelocation.DFTrubbersliderpadswerereplacedaftereverysixmeasurements.AlthoughtheASTMstandardallowstherubbersliderstobeusedfortwelvemeasurements,theaggressivewearonHFSTsurfacesrequiresmorefrequentreplacement.

• ThesequenceofDFTtestingandNCATTWPDconditioningwasasfollows:

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1. Onepairofslabswaspreparedfortestingandconditioning.2. InitialCTMandDFTmeasurementsweretakenoneachslab.3. TWPDconditioningfor70Kcycleswasperformedoneachslab.4. Theslabsweredriedovernight.5. CTMandDFTmeasurementsweretakenoneachslab.6. Anadditional70Kcyclesofconditioningwasperformedforeachslabmatching

thesameTWPDandslab.7. Theslabsweredriedovernight.8. FinalCTMandDFTmeasurementsweretaken.9. Thetestprotocolsequencewasrepeatedforeachsetofslabs.

TestResults

TheDFTmeasurementsarelistedinTable2andCTMmeasurementsarelistedinTable3.

TestQualityControl

Laboratorytestingconsistedof99setsofDFTmeasurements(threecycleperiods,threemeasurementspeeds,andelevenmaterials).TestingqualitycontrolexaminedthedifferencebetweentheDFTmeasurementsofthereplicateslabstodetermineifthetwoslabsforeachHFSTaggregategeneratedsimilarresults.Forexample,theaverageDFT(40)resultsfrom70KcyclesofTWPDforslab1werecomparedtothesameresultsforslab2.Differencesbetweentheslabmeasurementswerecombinedintoahistogramtoshowthedistributionofslabtestdifferences,showninFigure3.Overall,theaveragedifferencewasaDFTdeltaof0.034.Twostandarddeviationsfromthemeanwas0.08andonlythreedeltavaluesweregreaterthantwostandarddeviations.ThosevaluesarehighlightedinTable2.ThosetestvaluesrepresentinitialDFTtestsonunconditionedsurfacesandarenotcriticaltotheanalysis.

TheresultsofthisqualitycontrolanalysisweresimilartoanearlierHFSTstudypresentedinNCATreport15-04.Thatstudyobservedthat65%oftherangeswerebelow0.040and98%werebelow0.120.

CTMmeasurementsareveryrepeatable.Noqualitycontrolevaluationwasperformedonthedata.

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Table2SummaryofDFTResults

Table3SummaryofCTMResults

#Cycles km/h Slab1-Avg Slab2-Avg Slab1-Avg Slab2-Avg Slab1-Avg Slab2-Avg Slab1-Avg Slab2-Avg20 0.60 0.54 0.78 0.82 0.90 0.94 0.72 0.7240 0.62 0.55 0.81 0.88 0.95 0.97 0.75 0.7760 0.68 0.58 0.87 0.95 0.94 1.05 0.80 0.8320 0.50 0.52 0.55 0.56 0.78 0.81 0.54 0.4940 0.53 0.51 0.57 0.59 0.77 0.79 0.58 0.5360 0.51 0.55 0.57 0.61 0.74 0.79 0.64 0.5720 0.48 0.52 0.55 0.55 0.79 0.81 0.50 0.5040 0.52 0.52 0.57 0.56 0.79 0.80 0.53 0.5360 0.51 0.54 0.56 0.59 0.77 0.82 0.56 0.54

#Cycles km/h Slab1-Avg Slab2-Avg Slab1-Avg Slab2-Avg Slab1-Avg Slab2-Avg Slab1-Avg Slab2-Avg20 0.82 0.80 0.81 0.77 0.84 0.79 0.87 0.8240 0.86 0.82 0.84 0.80 0.86 0.79 0.85 0.8160 0.92 0.86 0.87 0.80 0.89 0.84 0.85 0.8120 0.62 0.61 0.60 0.59 0.58 0.55 0.59 0.6640 0.64 0.63 0.64 0.63 0.60 0.58 0.61 0.6760 0.66 0.66 0.66 0.61 0.65 0.59 0.63 0.7020 0.57 0.54 0.58 0.54 0.57 0.54 0.51 0.5740 0.60 0.58 0.60 0.57 0.59 0.57 0.52 0.5760 0.64 0.61 0.65 0.58 0.63 0.56 0.53 0.60

#Cycles km/h Slab1-Avg Slab2-Avg Slab1-Avg Slab2-Avg Slab1-Avg Slab2-Avg20 0.69 0.64 0.60 0.62 0.77 0.7840 0.70 0.67 0.62 0.66 0.80 0.8160 0.72 0.73 0.66 0.69 0.80 0.8220 0.45 0.44 0.41 0.43 0.51 0.5440 0.48 0.49 0.43 0.45 0.55 0.5760 0.51 0.50 0.45 0.49 0.57 0.6220 0.41 0.43 0.41 0.39 0.47 0.5140 0.45 0.46 0.43 0.41 0.47 0.5460 0.48 0.49 0.47 0.44 0.50 0.53

Basalt FlintRock-Flint RKBauxite CopperSlag

TractionControl

0cycles

70,000cycles

140,000cycles

0cycles

70,000cycles

140,000cycles

47-4x20 60-4x20 70-4x20 ArmorStone

0cycles

70,000cycles

140,000cycles

BestSand EP5MOD

Basalt FlintRock-Flint RKBauxite CopperSlag 47-4x20 60-4x200cycles 2.09 2.38 1.97 2.14 2.88 1.8170Kcycles 1.82 1.64 1.35 1.57 1.79 1.62140Kcycles 1.67 1.65 1.39 1.44 1.76 1.55

70-4x20 ArmorStone BestSand EP5MOD TractionControl0cycles 2.30 1.83 2.22 1.65 1.6270Kcycles 1.33 1.53 1.33 1.45 1.54140Kcycles 1.29 1.40 1.35 1.50 1.49

allvaluesareMTD(mm)

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Figure3SlabReplicateDFTComparison

DataAnalysis

Theanalysisfocusedontheterminal(70Kand140Kcycles)frictioncharacteristicsofthehighfrictionsurfaces,includingthechangeinvaluesbetweenthe70Kand140Kmeasurementincrement.Thecomparisonofthechangeintestmeasurementsbetween70Kcyclesand140Kcyclesisparticularlyimportanttodetermineiftheaggregatereachedaterminalfrictioncondition.Figure4displaystheDFTfrictionresultsforallaggregatestested.Figure5displaystheCTMmacrotextureresultsforallaggregatestested.TheCTMsurfacetexturedatashowsallsurfaceswithMTDmacrotextureintherangeof1.2to1.8mm,whichiscommonforHFSTafterconditioning.Incomparison,typicalconventionaldense-gradeasphaltmixtureshaveterminalmacro-texturebelow0.60mmandporousmixturesarebelow1.2.Figure6displaysthe140KterminalDFTfrictionandCTMsurfacetextureterminalvaluesfortheelevenaggregates.Similartopreviousstudies,thereisnocorrelationbetweenmeasuredfrictionandsurfacemacrotextureforHFSTsurfaces.

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Figure4ComparisonofLaboratoryFrictionPerformance

Figure5ComparisonofLaboratorySurfaceTexturePerformance

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Figure6CorrelationofFrictionandSurfaceMacrotexture

ThelegendinFigure4placestheaggregatesinorderfromhighestfrictionafter140KpolishingcyclestolowestfrictionbasedonDFT(40)values.Fromthesummaryofthefrictiontesting,thefollowingobservationsaremade.

• Calcinedbauxitemaintainshigherfrictionthanallotheraggregatesinthestudy.• AllthreeproductsfromRoswell,GAandFlintRockdisplayedsimilarhighperformance

comparedtootheraggregates(exceptbauxite).• ArmorStonecontinuedtopolishbetween70Kcyclesand140Kcycles.Basedon140Kcycle

ranking,itfallsintoamiddlecategory,butat70Kcyclesitwasperforminginahighercategory.

• CopperslagandTractionControlshowedsimilarmiddlecategoryfrictionperformance.• Basaltdisplayedconsistentfriction,losingminimalfrictionperformancefrom0cyclesto

140Kcycles.TheaggregatehaslessangularitypriortopolishingasnotedbythelowDFT(40)at0cycles,buthasverygoodpolishresistanceasshownbytheminimalfrictionlossafterpolishing.

• BestSandandEP5MODdemonstratedthelowestfrictionperformance.

BasedonapreviousFHWAstudyonHFSTfriction,laboratoryterminalfrictionvaluesarehigherthanfieldterminalfrictionvalues,asshowninFigure7(7).UsingtheFHWAstudy’scorrelation,theexpectedterminalfieldfrictionwouldbeapproximately40(SN40R)fortheRoswellproductsandFlintRock.

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Figure7CorrelationofLaboratoryandFieldTerminalFrictionValues(7)

CONCLUSIONSANDRECOMMENDATIONS

Thisstudycomparedthelaboratoryperformanceof11differentfrictionaggregatespreselectedbytheagency.ThestudyfocusedonlaboratorytestmeasurementsthatresembleaterminalfrictionconditionafterpolishingwiththeNCATThreeWheelPolishingDevice.Thefriction,measuredbytheDynamicFrictionTester,hasawiderangefrom0.40to0.80,indicatingthattherewasasubstantialdifferenceinfrictionperformancebetweenaggregates.Themacrotexturerange,measuredasmeantexturedepth,wascommonforHFSTafterconditioning.TherewasnocorrelationbetweenmeasuredfrictionandsurfacemacrotextureforHFSTsurfaces.

ItistheresponsibilityofthegoverningagencytodetermineanacceptablethresholdforHFSTperformance.Thesuccess(reductionincrashes)oflocallyplacedsectionswithregionallyavailablefrictionaggregatemaybeanappropriateapproachforsettingacceptablematerialthresholds.

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REFERENCES

1. EveryDayCounts:ReportontheEDC2Summits.FHWA,U.S.DepartmentofTransportation,2013.

2. HighFrictionSurfaceTreatmentsFrequentlyAskedQuestions.ReportFHWA-CAI-14-019.FHWA,U.S.DepartmentofTransportation,2014.

3. MichiganDepartmentofTransportation.SpecialProvisionforHighFrictionSurfaceTreatment.12SP-800A-03.http://mdotcf.state.mi.us/public/dessssp/spss_source/12SP-800A-03.pdf.

4. MichiganDepartmentofTransportation.SpecialProvisionforThinEpoxyPolymerBridgeDeckOverlay.12SP-712B-01.http://mdotcf.state.mi.us/public/dessssp/spss_source/12SP-712B-01.pdf.

5. Vollor,T.,D.Hanson.DevelopmentofLaboratoryProcedureforMeasuringFrictionofHMAMixturesPhaseI.NCATReport06-06.NationalCenterforAsphaltTechnology,Auburn,Ala.,2006.

6. Erukulla,S.RefiningaLaboratoryProceduretoCharacterizeChangeinHot-MixAsphaltSurfaceFriction.MSthesis.AuburnUniversity,Auburn,Ala.,2011.

7. Heitzman,M.,P.Turner,M.Greer.HighFrictionSurfaceTreatmentAlternativeAggregatesStudy.NCATReport15-04.NationalCenterforAsphaltTechnology,Auburn,Ala.,2015.