EvaluatingthePerformanceofTackCoatMaterialsinSaskatchewanClimatebyMeansofaFieldStudyandLaboratoryStudy–Part1FieldStudy

LauraStasiuk,M.Sc.Candidate

ResearchAssistantUniversityofSaskatchewan

HaithemSoliman,Ph.D.AssistantProfessor

UniversityofSaskatchewan

AniaAnthony,M.Sc.,P.Eng.Director,MaterialsandSurfacing

SaskatchewanMinistryofHighwaysandInfrastructure

ChrisDechkoff,P.Eng.TechnicalManager

ACPAppliedProducts

JenPenner,M.Sc.Candidate,EITAssetIntegrityEngineer

PounderEmulsions(HuskyEnergy)

PaperpreparedforpresentationattheTestingandModelingofRoadandEmbankmentMaterialsSession

ofthe2018ConferenceoftheTransportationAssociationofCanada

Saskatoon,SK

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ABSTRACTTackcoatmaterialsareusedtoprovidesufficientbondbetweenanexistingasphaltconcretelayerandanewasphaltconcreteoverlayand/orin-betweentwoliftsofnewlyplacedasphaltconcrete.Mostofthetime,agenciesandcontractorsrelysolelyonemulsifiedbituminousproductsforuseastackcoats.Recentdevelopmentsintackcoatmaterialsarefocusingonfastcuringandnon-trackingemulsions.TheobjectiveofthisprojectistoevaluatetheperformanceofseveraltackcoatmaterialsinSaskatchewanclimatethroughafieldstudyandalaboratory-testingprogram.TentestsectionswereconstructedinAugust2017onatwo-way,two-laneruralhighway(Highway12)nearBlaineLake,Saskatchewan.Constructionandinstallationofthetackcoatmaterialswascompletedovertwodaystoeliminateanyvariabilityduetoweatherconditions.Apost-constructioninspectionwasconductedinSeptember2017todocumentanysurfacedistressesrelatedtotheconstructionprocess.Adistresssurveywillbeconductedfollowingthespringseasonofeachyearfor5years.CoresampleswerecollectedinSeptember2017toevaluatetheinitialbondstrengthofthetackcoatmaterials.Coresampleswillbecollectedfollowingthespringseasonofeachyeartoevaluatethedegradationofbondstrengthovertime.Findingsfromthisprojectwillbeusedtoupdatetheapprovedtackcoatmaterialslistandproviderecommendationsandguidelinesforconstructionbestpractices.Thispaperintroducestheexperiment,discussestheproductsused,andprovidesasummaryofobservationsfromthefieldcomponentoftheproject.

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1. BACKGROUNDCurrentindustrystandardswidelyoverlooktheimportanceofatackcoatintheperformanceofpavementstructures.Tackcoatsarebituminousmaterialsusedtoprovidebondingbetweenasphaltlayers.Typically,theindustryhasbeenrelyingonemulsifiedasphaltproductsforthispurpose.Anidealtackcoatmaterialwouldhaveshortbreakandsettimestolimittheinconveniencetothecontractorandtothepublicwhicharisefromlongcuringtimes.Shortbreakandsettimesensureachievingproperbondbetweenasphaltconcretelayerswithoutslowingdowntheconstructionprocess.Inaddition,shortbreakandsettimesreducepickupandtrackingofemulsionresidueonconstructionequipmentandontravelingvehicleswhichoccasionallyenduptravelingonatackedroadsurface.Atackcoatmaterial“breaks”whenitscolourchangesfrombrowntoblackasshowninFigure1.Breaktimesvarysignificantly,dependingonthepropertiesofthematerialitself,whetherandhowitisdilutedwithwater,aswellaswithweatherconditions.Atackcoatsetswhentheemulsionresidueisnolongerpickedupfromtheroadsurface.Thiscanbedeterminedbyblottingthesurfacewithatissueontheemulsion,andbyobservingproducttransfertovehicletires.Minimaltransferofresidueindicatesthatanywaterpreviouslypresentinthematerialhasevaporatedandtheasphaltbitumenisformingahomogeneouslayerontheroadsurface.

Figure1.BrokenandUnbrokenTackCoatMaterial

Achievingsufficientproperbondstrengthbetweenasphaltconcretelayersiscriticaltoensurethatthebondedlayerswillactandresiststressesasonehomogeneoussystem.Ifthebondisinadequate,asphaltconcretelayerswillactseparatelyasmultiplelayerswhichwillincreasethestresslevelswithintheselayersandleadtocrackingandprematurefailure.Figure2showsthedifferenceinasphaltconcretelayersbehaviourwithgoodandpoorbond.InFigure2bapoorbondbetweennewandoldasphaltconcretelayersmakesthetwolayersactindependentlyastwothinlayers,whichleadstoexceedingthetensilestrengthofasphaltconcreteandcrackingofthenewasphaltlayer.

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Figure2a.OldandNewACLayersActasOneThickLayerFigure2b.OldandNewACLayersActasTwoSeparateLayers

Figure2.BehaviourofAsphaltConcreteLayerswithGoodandPoorBond

TherehasnotbeenalotofstudyfocusontheeffectivenessoftackcoatmaterialsinCanadianclimate.Pastindustrystudiesreviewedthebondstrengthandapplicationproceduresoftackcoatmaterials,however,thesestudiesdidnottakeintoaccounttheextremeweatherconditionsexperiencedinSaskatchewan.ArecentcomprehensivestudywasperformedbytheTransportationResearchBoard(TRB)andissummarizedinatechnicalpublicationtitledNCHRP712:OptimizationofTackCoatforHMAPlacement[1].Thisstudyexploresmultipleaspectsoftackcoatproceduresincludingapplicationrates,effectsofpoorconstructionpractices,developmentofaninsitutackcoatqualitytest,andthedevelopmentofalabtest(AASHTOTP114).AworldwidesurveywasalsoconductedaspartofthestudytogainknowledgeaboutthemethodsagenciesinNorthAmericaandaroundtheworlduseforconstructionpractices,andqualityassurance[1].AccordingtotheworldwidesurveyconductedaspartoftheNCHRP712project,26%ofthesurveyedagenciesallowconstructiontruckstodriveonunbrokenemulsion.Furthermore70%ofthesurveyedagenciesallowconstructiontrucksonbrokenemulsionbeforeithasset.Outofthe53surveyedagencies,74%oftheagenciesallowpavingtobeginimmediatelyafterthetackcoatmaterialbreaks,whereas26%donotallowpavinguntilthetackcoatemulsionsets.92%ofthesurveyedagenciesstatedthattheydonottesttomeasurethebondstrengthattheinterfacebetweenAClayers.Basedontheabovestatistics,thereisclearlyaneedforfastbreakingandsettingtackcoatmaterialsandbetterconstructionpracticesandmonitoring[1]..TheNCHRP712reportidentifiedtwentytestingmethodsusedbyagenciesfortackcoatbondsincludingbothlaboratoryandin-situtests.Mostofthesetestsmeasureshearstressortensilestrength.SomeofthesetestsincludetheLeutnerShearTest,FloridaDirectShearTest,andtheSwitzerlandPullOffTest[1].Astudyhasbeenperformedin2017atOregonStateUniversitytodeveloptheOregonFieldTorqueTester(OFTT)[2].Thisin-situbondstrengthtesteroffersacheaperandlessdestructivemethodoftestingforinterlayershearstrength.TheOFTTrequiressmallercoresamplesthanpreviouslymentionedmethods.Coresdiametersare2.5inchesandnottakenatfulldepth.TheOFFTdevicesmeasurespeaktorqueinthefield.PeaktorquewascorrelatedwithlabinterlayershearstrengthresultsobtainedfromfollowingtheAASHTOTP

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114procedure.FieldresultsfromtheOFTTwerehighlycorrelatedwiththeshearstrengthresultsofcoresamplesinthelab[2].Severalstudiesreviewedthebestpracticeoftackcoatapplication.DestréeandDeVisscher(2017)concludedfromafieldstudythattherewasnosignificantdifferencebetweenthebondstrengthofcoresthathadbeenexposedtovaryinglevelsofpressurewashingonmilledsurfacepriortotackcoatapplication[3].AstudyfromtheLouisianaTransportationResearchCenterin2010foundthatroughnessoftheunderlyinglayerhadaneffectonbondstrength;amilledHMAyieldedthehighestbondstrengthfollowedbyanexistingunmilledlayerandthenanewHMAlift[4].Tackcoatapplicationproceduresarenotwelldefinedorfollowedbymanytransportationagencies.Someconstructionpractices,suchasallowingdeliverytruckstodriveonthetackcoatbeforeitisset,oftendonotleaveenoughtackcoatmaterialinthewheelpathstoformastrongbondbetweentheasphaltconcretelayers.Poorbondingcontributestoearlydeteriorationofroadsbecausethestressesandstrainsintheasphaltconcreteexceedthedesignlimits.Mostengineersarefamiliarwiththeextremecasesofbondfailures,asshowninFigure3.However,theeffectsofpoorbondingcanalsobesubtleandinsteadofcatastrophicfailures,maymanifestthemselvesmoregradually,intheformofacceleratedfatiguecracking(asshowninFigure4),ofteninthelaterstagesofthepavementlifecycle.Basedoncurrentpractice,tackcoatmaterialstypicallycostbetween1and1.5%oftotalpavementcost.Ifthebondisweak,theresultingcostscanamountto30%andallthewayupto100%oftotalpavementcost[5].Ensuringthatanadequatebondisformedbetweenpavementlayerswillmaximizetheagencypavingbudgetsandtaxpayerinvestmentintoroadinfrastructure.

Figure3.ExampleofSlippageFailuresfromPoorBondingBetweenAsphaltLayers

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Figure4.ExampleofFatigueCracking

SaskatchewanMinistryofHighwaysandInfrastructure(SMHI)isinterestedinexpandingtheirrepertoireoftackcoatasphaltemulsionproducts.SMHIspecificationscurrentlylimittackcoatmaterialstothebasicslowsettingemulsions,SS-1andSS-1h.SMHIisinterestedintestingthebondstrengthandmeasuringfieldparametersofseveraltackcoatmaterialsavailableinSaskatchewantoevaluatetheireffectiveness,andthebestapplicationpracticestofollow.Tocarryoutthisproject,SMHIpartneredwiththeCityofSaskatoon,ACPAppliedProducts,PounderEmulsions(HuskyOil)Ltd.,McAsphaltIndustriesLtd.,Colasphalt,andtheUniversityofSaskatchewan.TheperformanceofseveraltackcoatmaterialswillbeevaluatedintheSaskatchewanclimatethroughafieldstudyandlaboratorytestingprogram.Resultsfromthefieldstudyandthelaboratorytestingwillbeusedtodevelopperformancebasedspecificationsforselectionoftackcoatmaterials,andtorecommendtackcoatapplicationbestpractices.Thisresearchaimstooptimizeroadconstructionandmaintenancecostsandpreventprematurepavementfailures.Thispaperpresentsthepreliminaryresultsofthefieldstudyandthefuturestepsforthisproject.

2. MATERIALSSeventackcoatmaterialsprovidedbyindustrypartnerswillbeevaluatedinthisstudy.Threeslowsettingemulsionswereprovided:SS-1,SS-1h,andacationicSS-1h(CSS-1h).Ananionicmediumsettingemulsion,MS-1,wasalsotested.TheslowsettinganionicemulsionSS-1wastestedinthreesectionsandSS-1hwastestedintwosections.SS-1willbeusedasthecontrolmaterialforcomparisonbecauseitisthetypicalmaterialusedinallSaskatchewanHighwaysprojects.Threefastbreaking/quicksettingproprietaryproductswerealsoprovidedbytheindustrypartners;theseproductsarelabelledasA,B,andCthroughoutthepaper.Twosamplesofeachproductweretakenfromthedistributoratthetimeofapplication.Thesesamplesweresenttotwoindustrypartnerlabsforqualitycontroltesting.Testsincluded:

• ASTMD5:StandardTestMethodforPenetrationofBituminousMaterials[6]

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• ASTMD6997:StandardTestMethodforDistillationofEmulsifiedAsphalt[7]• ASTMD7175:StandardTestMethodforDeterminingtheRheologicalPropertiesof

AsphaltBinderUsingaDynamicShearRheometer[8]• ASTMD7404:StandardTestMethodforDeterminationofEmulsifiedAsphaltResidue

byMoistureAnalyzer[9]• ASTMD7496:StandardTestMethodforViscosityofEmulsifiedAsphaltbySayboltFurol

Viscometer[10]Bothlabsprovidedsimilarresultsindicatingconsistenciesintesting.InTable1belowarethequalitycontrolresultsprovidedbythemanufacturerspriortoconstruction.Table1.MeasuredPropertiesforTackCoatMaterialsfromSuppliersPriortoConstruction

Product SS-1 SS-1h CSS-1h MS-1 A B C

ResiduebyDistillation(%b.w.)-ASTMD6997 60.1 61.3 61 59.5 55.6 61.4 58.9OilPortionofDistillate(%b.v.)-ASTM6997 0.5 0.5 1.0 0.8 0.5 0.5 2Penetration(dmm)-ASTMD5 130 69 95 151 70 46 135

3. METHODLOGYThisresearchprojectiscomprisedofafieldstudyandalaboratorytestingprogram.Thefieldstudywillevaluatetheconstructabilityandperformanceoftackcoatmaterialsinnormalfieldconditions.Constructionandenvironmentaldatawererecordedatthetimeofinstallationoftackcoatmaterials.Apost-constructiondistresssurveywascompletedtodocumentearlydistressesrelatedtotheconstructionprocess.Futuredistresssurveyswillbeconductedfollowingeachwinterseasonforfouryears.Inadditiontodistresssurveys,coresampleswerecollectedafterconstructiontoevaluatetheinitialbondstrength.Additionalcoresampleswillbecollectedfollowingeachwinterseasontoevaluatethedeteriorationonbondduetotrafficloadingandenvironmentalconditions.Thelaboratorytestingprogramfocusesontestingthebondstrengthofthetackcoatmaterialsusingthecoresamplescollectedfromthefieldtestsections.BondstrengthtestswillbeconductedaccordingtoAASHTOTP114:DeterminingtheInterlayerShearStrength(ISS)ofAsphaltPavementLayers[11].Partofthepost-constructioncoresampleswillbeconditionedinthelabunderacceleratedfreeze-thawcyclingtosimulatefieldconditionsincoldregions.Resultsofthebondstrengthtestsforlabconditionedandfieldconditionedcoresampleswillbecomparedandusedtoestablishguidelinesandproceduresforacceleratedtestingoftackcoatmaterials.

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A1.1kmtwo-way,two-laneroadsegmentonHighway12nearBlainLake,SK,wasdesignatedforthefieldstudy.Withinthisroadsegment,tentestsectionswereconstructed,fiveineachlane.ThelayoutoftheproductsandtestsectionswithintheroadsegmentisshowninFigure5.

Figure5.LayoutofTestSectionsandTestedMaterials

Eachtestsectionwasapproximately225minlengthandwasfurtherdividedintospecificareas.Theseareasarecalibration/applicationratetestingarea,pickupandtrackingtestingarea,non-destructivetesting(NDT)area,andtwocoringareas.Figure6showsaschematicofthefieldtestsection.

Figure6.TestSectionSchematic

Thefirstareawasthecalibration/applicationratetestingarea.This25mareawasusedtocalibratethedistributorbymeansofapatchtest.Apatchtestwasperformedtoensurethedistributorwasapplyingaconsistentdesiredsprayrate[12].Elevenabsorbentpatcheswereplacedontheroad.Thedistributorsprayedthisfirst25mareaandstopped.Patcheswereweighedandactualapplicationratewouldbedetermined.Adjustmentsweremadetothedistributoron-boardratecontrolcomputerifnecessary.Figure7showsalayoutforthepatchtest.

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Figure7.PatchTestLayout[12]

Oncethecalibrationofthedistributorwasfinalized,theremaining200mwassprayed.Thisincludedthepick-upandtrackingtestingarea,non-destructivetesting(NDT)area,andthetwocoringareas.Thesecondareawasthepick-upandtrackingtestarea.This25mareawasusedtoevaluatethebreakingandsettingtimesaswellasthematerialseveritytopick-up/trackingbytrucktires.Oncetheproducthadset,atruckwasdrivenoverthesectionandthematerialwasgivenaratingofnone,low,medium,orhighaccordingtoitspick-up/trackingbytrucktires.Thethirdareawasthenon-destructivetestingarea.This125mareawillbeusedtoperformthedistresssurveyfollowingwinterofeachyear.Fallingweightdeflectometer(FWD)testingmaybeperformedaswell.Thelastareasarethetwocoringareas.Eachcoringareawillhave32coresextractedfromitduring5coringperiods.Thefirstsetofeightcoreswascollectedfromeachzonefollowingthecompletionofconstruction.ThesecoresareredinFigure8below.Coreswerecollectedfromtheinnerandouterwheelpaths(IWP&OWP),andthecentreofeachlane.Table2showsabreakdownofthecorescollectedpost-construction.Theremaining24coreswillbetakenfromtheroadfollowingthewintersofyears2018,2019,2020,and2021.

Figure8.CoringMap

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Table2.Post-ConstructionCoringCounts

CoringArea1 CoringArea2

IWP OWP Centre IWP OWP Centre TotalZone1

TotalZone2

TotalIWP

TotalOWP

TotalCentre Total

3 3 2 3 3 2 8 8 6 6 4 16

4. FIELDSTUDYTheconstructionofthetackcoattestsectionwascompletedonAugust22and23,2017.ThelocationofthetestsectionsisonSaskatchewanHighway12justsouthofBlaineLake(approximately80kmfromSaskatoon).Thishighwayisatwo-way,two-laneruralhighway.Resurfacingofthishighwaywasunderwayandaportionofthehighwaywasallocatedtothetackcoatfieldstudy.Theresurfacingprojectinvolvedmilling30mmoftheoldasphaltsurfaceandlayingtwoliftsofasphaltconcrete,each50mminthickness.A1.1kmroadsegmentwasdesignatedfortheresearchproject,andthetestsectionswereplacedoncebottomliftasphaltconcretewascompleted.Asaresult,thisstudyfocusesonevaluatingthebondcreatedbetweenthetwonewlayersofasphaltconcrete.Constructiontookplaceovertwoconsecutivedaystominimizedifferencesinweatherconditions.Whileeffortsweremadetominimizethedifferenceinweatherconditions,therewasstillsomevariationintemperatureandhumidity.Sectionsconstructedinthemorningwereexposedtocolderandmorehumidconditionsthansectionsconstructedlaterintheafternoon.Temperaturesduringconstructionwerebetween11°Cand24°C.Humiditywasbetween39%and85%.Whiletheconstructiontookplace,parametersrelatedtomaterials,weather,andconstructionprocesswererecorded.Therecordedinformationaboutthetackcoatmaterialsweredilution%,tackcoatapplicationtemperature(atthesprayernozzle),breaktime,settime,andpick-up/trackingrating.Therecordedweatherinformationparameterswere:airtemperature,windspeed,pavementtemperature,humidity,andweathercondition.Therecordedconstructioninformationwastargetapplicationrate,actualapplicationratefrompatchtest,andaverageapplicationratefromthedistributordata.Table3belowshowstheresultsofthepick-up/trackingtest,andbreakingandsettingtimes.Someproductsdidnotbreakandsetbeforepavingoccurredsoatrackingtestwasnotperformed.Table4containstherecordedfieldparameters.

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Table3.Pick-Up,BreakTimes,andSetTimesProduct Pickup

RatingBreakTime

(min)SetTime(min)

SS-1(50-50W)SB None 79 134SS-1h(50-50W)SB N/A N/A N/AA None 10 120MS-1(70-30W) Medium 20 49SS-1(30-70W) N/A N/A N/ASS-1(50-50W)NB N/A 360 N/ACSS-1h(50-50W) None 30 68C None 5 14SS-1h(50-50W)NB N/A N/A N/AB None 3 10Note:ProductsthatcontainN/Aforpickupratingwerenotsubjectedtoatracking/pickuptestduetothematerialtakingtoolongtobreakandset.Atrackingtestwasonlyperformedonsetmaterial.MaterialswithN/Aforbreakandsettimeswerepavedwithouthavingthetackcoatmaterialset.Table4.FieldParameters

ProductName:

SS-1(SB) SS-1 SS-1

(NB)SS-1h(SB)

SS-1h(NB) CSS-1h MS-1 A B C

Dilution(%):

50-50W

30-70W

50-50W

50-50W

50-50W

50-50W 70-30W 0 0 0

AppTemp(°C): 26.3 40 31 30.1 42.2 36.3 32.3 32.0 49.7 40.8

PavementTemp(°C): 20 37 24 31 40 33 42 37 35 41

TargetAppRate(L/m2):

0.5 0.5 0.5 0.5 0.5 0.5 0.41 0.36 0.33 0.33

ActualAppfromPatchTest(L/m2):

0.50 0.28 0.52 0.45 0.21 0.47 0.36 0.27 0.23 0.28

AirTemp(°C)*: 14 22 11 16 24 17 22 20 24 22

Humidity(%)*: 64 48 85 50 39 65 44 47 43 49

WeatherCondition*:

PartlyCloudy -- Sunny -- Sunny Sunny Sunny Partly

Cloudy Sunny Sunny

Wind(km/h)*: -- 2 11 8 18 10 10 9 17 17

*WeatherparametersfromTheWeatherNetworkConstructionofthetestsectionswasdoneaccordingtotheplanandlayoutoutlinedinthemethodologysection.Thedistributorusedtoapplythetackcoatmaterialswasa2015BearCat

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ComputerRateControlledDistributorandisshownbelowinFigure9.Thenozzlesweresetataheightof15-20cmfromtheground,withanozzleangleof30degreeswhichallowedfortripleoverlaptobeachieved.Thedistributorcomputerwassettosprayaconstantapplicationrateindependentofthetruck’sspeed.Thedistributor’ssetapplicationratewasadjustedbasedonthetackcoatmaterial’sdilutionpercentagetoaimforthesameresidualapplicationrateforallproducts.Thedifficultyinspraying10productsofbothanionicandcationicvarietieswithinatwodayperiodwasachallengetothecontractorasthedistributorhadtobeflushed(cleaned)betweenproductstoensurethattherewerenocontaminationbetweentheproducts.

Figure9.TackCoatDistributorTruck

Thetracking/pickuptestwasperformedonsixofthetentestsections.ThefoursectionsthatwerenottestedweretwotestsectionsofSS-1h(both50-50W)andtwotestsectionsofSS-1(30-70Wand50-50W).Theproductstooktoolongtobreakandsetandthesetimescouldnotbemonitoredfully.Performingatrackingtestontheseproductsbeforetheysetwouldnothaveofferedanyvaluableinformationbecausethetrackingwouldhavebeensevere.Figure10showstheroadfollowingcoringandtheeightfour-inchcorestakingfromacoringarea.Coreholeswerefilledwithacoldmixasphalt.Coresweredrilledusingacoringdrillmountedonthebackofapickuptruck.Followingextraction,eachcorewaslabelledbasedontestsectionnumber(1-10),coringzonenumber(1or2),andlocationintheroad(innerwheelpath,centre,orouterwheelpath.Coreswerecarefullywrappedinbubblewraptopreventdamageduringtransportandwhileinstorage.Coreswerestoredatroomtemperature.

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Figure10.Cores

5. CONSTRUCTIONOBSERVATIONS

TheapplicationratesselectedforeachtackcoatproductweredeterminedbasedonbestpracticessetoutinthepreviousworkcompletedanddocumentedintheNCHRP712[1].Thepavingcontractorrepresentativescommentedthatingeneral,theapplicationratesthatwerebeingusedforthetestsectionsfarexceedtheapplicationratestypicallyseenonSMHIprojects.ThisisdirectlylinkedtothefactSS-1takesalongtimetobreakandset,andasaresult,SMHIhastraditionallyusedlowerapplicationratestoallowforfastersetting,andtominimizepickupofmaterialinwheelpaths.EventhoughSMHIbegantoincludespecifiedminimumapplicationratestwoyearsago,thepracticeofincreasingratesforbetterbondinghasnotyetbeenwidelyadopted.ThisisalsoduetothefactthatSMHIhasbeenreluctanttoenforcetheminimumrateswithouthavingavarietyoftackcoatproductsapprovedandavailableforcontractorstoselectfrom.Fromthetraditionaltackcoatemulsionsthatweretested,itwasveryclearthattheCSS-1hbrokeandsetfasterthanSS-1.ThesamewastruefortheMS-1emulsion.Further,thethreeproprietaryproductstestedweresuperiorintheirbreakingandsettingtimes.Unfortunately,thefirstSS1-hsectiondidnotbreakevenafterseveralhours.Whenthiswasevident,anadditionalsectionofSS-1hwasconstructed,however,thesameproblemwasencountered.Itissuspectedthateitherthedilutionwateraffectedtheproduct,ortherewerepossibleresidualchemicalsinthetotesinwhichtheemulsionwasshipped,whichimpactedtheperformance.Therefore,theSS-1hfieldobservationsareinconclusive.Thebreakandsettimesofthetestedproductswereplottedwithtemperaturereadingstoseeifanytrendscanbeobserved.FromFigure11,itcanbenotedthatbreakandsettimesshowedsomecorrelationtopavementtemperature,airtemperature,andproducttemperature.Asapplicationtemperature,airtemperature,andpavementtemperatureincrease,thebreakandsettimesdecrease.Thisindicatesthattemperaturehasaneffectontheseparameters.Inaddition,Figure12showsacorrelationbetweenhumidityandbreakandsettimes.Figure12

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showsthatlowerhumiditycorrelatestofasterbreakingandsettingtimes.Alowerhumiditylevelacceleratestheevaporationrateofwaterfromthetackcoatmaterials.

Figure11.PlotofBreakandSetTimeswithTemperature

Figure12.PlotofBreakandSetTimeswithHumidity

6. SUMMARY&FINDINGSThisresearchprojectiscomprisedofafieldstudyandlaboratorytestingprogram.Thefieldstudyexaminedtheperformanceandcontractibilityparametersforsevenproducts:SS-1,SS-1h,CSS-1h,MS-1,andthreesupplierproprietarytackcoatproducts.Thesevenproductswereinstalledintentestsections.Apost-constructiondistresssurveywasconductedonemonthafterconstructioncompletionandindicatednodeficienciesduetoconstruction.Atthesametimeasthepost-constructiondistresssurvey,coreswerecollectedfromeachofthetentest

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sectionstomeasuretheinitialbondstrengthofthetackcoatmaterials.Monitoringofthefieldtestsectionswillcontinueuntil2021.Thefieldcoreswillbetestedinthelaboratoryforbondstrengthoftackcoatmaterials(interlayershearstrength)accordingtoAASHTOTP114:DeterminingtheInterlayerShearStrength(ISS)ofAsphaltPavementLayers.Partofthepost-constructioncoreswillbesubjectedtoacceleratedconditioninginthelaboratoryunderfreezethawcyclingpriortobondstrengthtesting.Earlyresultsshowreducedtrackingforproprietaryproductswhichhavefasterbreakingandsettingtimesthanslowsettingtackcoatmaterials.TheslowsettingemulsionsCSS-1handMS-1brokeandsetfasterthanSS-1.TheseearlyresultsindicatethatusinganyofthetestedproductsinsteadofSS-1maybebeneficial.Supplierproprietaryproductswerethefastesttobreakandsetandprovedsuperiorintrackingandpick-upperformance.Bondstrengthtestingandlong-termresistancetofreeze-thawcyclingwillconfirmifthesematerialsaresuperiorintheirperformanceaswell.Finally,thedatarecordedduringconstructionofthetestsectionsshowsthatbreakandsettimesarecorrelatedtoairtemperature,pavementtemperature,applicationtemperature,andhumidity.

7. ACKNOWLEDGEMENTSTheauthorsaregratefulto:SaskatchewanMinistryofHighways&Infrastructure,TheCityofSaskatoon,SaskatchewanCentreofExcellenceforTransportationandInfrastructure(SCETI),ACPAppliedProducts,PounderEmulsions(HuskyOil)Ltd.,McAsphaltIndustriesLtd.,andColasphaltforsupportingthisresearch.

8. REFERENCES

1) TransportationResearchBoard(TRB).2012.NationalCooperativeHighwayResearchProgram(NCHRP)712OptimizationofTackCoatforHMAPlacement.Washington,DC.

2) Mahmoud,A.,Coleri,E.,Batti,J.,Covey,D.2017.“DevelopmentofaFieldTorqueTest

toEvaluateIn-SituTackCoatPerformance.”ConstructionandBuildingMaterials.Volume135:377-385.

3) Destrée,A.,DeVisscher,J.2017.“ImpactofTackCoatApplicationConditionsontheInterlayerBondStrength.”EuropeanJournalofEnvironmentalandCivilEngineering,21:sup1,3-13.

4) Mohammed,L.,Bae,A.,Elseifi,M.,Button,J.,Patel,N.2010.“EffectsofPavement

SurfaceTypeandSamplePreparationMethodonTackCoatInterfaceShearStrength.”

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TransportationResearchRecord:JournaloftheTransportationResearchBoard,No.2180,pp.93-101.

5) AsphaltInstitute.2014.“TackCoatBestPractice”Webinar.

6) ASTMStandardD5,2013,"StandardTestMethodforPenetrationofBituminous

Materials,"ASTMInternational,WestConshohocken,PA.

7) ASTMStandardD6997,2012,“StandardTestMethodforDistillationofEmulsifiedAsphalt,”ASTMInternational,WestConshohocken,PA.

8) ASTMStandardD7175,2015,“StandardTestMethodforDeterminingtheRheologicalPropertiesofAsphaltBinderUsingaDynamicShearRheometer,”ASTMInternational,WestConshohocken,PA.

9) ASTMStandardD7404,2007(2016),“StandardTestMethodforDeterminationof

EmulsifiedAsphaltResiduebyMoistureAnalyzer,”ASTMInternational,WestConshohocken,PA.

10) ASTMStandardD7496,2011,“StandardTestMethodforViscosityofEmulsifiedAsphalt

bySayboltFurolViscometer,”ASTMInternational,WestConshohocken,PA.

11) AASHTOTP114,2015,“StandardMethodofTestforDeterminingtheInterlayerShearStrength(ISS)ofAsphaltPavementLayers,”AmericanAssociationofStateHighwayandTransportationOfficials,Washington,DC.

12) WSP.2017.“ProcedureforDistributorCalibrationTest.”