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MASSON,AdhesionMechanisms,1/16AREVIEWOFADHESIONMECHANISMSATTHECRACKSEALANT/ASPHALTCONCRETEINTERFACEJ-F.MassonandM.A.LacasseInstituteforResearchinConstruction,NationalResearchCouncilofCanada,CanadaAbstractExistingadhesiontheoriesandassociatedmechanismsarereviewedandappliedtobituminouscracksealantsandtothecracksealingofasphaltconcrete(AC)roadways.Assuch,thepossiblecontributionofeachmechanismtothesealant-interface-ACsystemiscriticallyassessed.Ofsixpossibleadhesionmechanisms,onlysealantadsorptionandinterlockcanexplainadhesionbetweensealantandAC.Inthisregard,intrinsicsealantpropertiessuchasviscosityandcompositionareparticularlyimportant.Incontrast,sealantfailurecanbeexplainedbestbythepresenceofdefectsatthesealant-ACinterfacesuchasdust,voidsandmicrocracks.Theexistenceofthesedefectsismorecloselyrelatedtosealantinstallationthantothesealantitself.Intheend,thereviewallowsfortheidentificationofmanyfactorsthatmustbebetterunderstoodifsealantadhesionandperformanceistobeenhancedsignificantly.RésuméLesthéoriessurl’adhérenceetlesmécanismesconnexessontanalyséesetappliquéesauxbouche-fissuresbitumineuxetàl’obturationdesroutesenbétonasphaltique.Àcetitre,ellesfontl’objetd’uneévaluationcritiquedelacontributionpossibledechacundesmécanismesàl’interfacebouche-fissures/bétonasphaltique.Dessixmécanismesd’adhérencepossibles,seulesl’absorptionetl’imbricationpeuventexpliquerl’adhérenceentrelebouche-fissuresetlebétonasphaltique.Àcetégard,lespropriétésintrinsèquesdubouche-fissurescommelaviscositéetlacompositionrevêtentuneimportanceparticulière.Parcontre,ladégradationdubouche-fissurespeutmieuxs’expliquerparlaprésenced’irrégularitésauniveaudel’interfacebouche-fissures/bétonasphaltiquetellesquelapoussière,lesvidesetlesmicro-fissures.L’existencedecesirrégularitésestdavantageimputableàlaposedubouche-fissuresqu’aubouche-fissureslui-même.Enfin,cetteanalysepermetdedéterminerdenombreuxfacteursquidoiventêtremieuxcomprissil’onveutaméliorerdemanièreconsidérablel’adhérenceetlaperformancedesbouche-fissures.1.IntroductionBituminoussealantsareusedtosealcracksinasphaltconcrete(AC)pavements.InmanyNorth-Americancitieswhichexperiencecoldwinters,recommendedcracksealingproceduresincludethecleaning,theroutingandtheheatingofcracks[1,2].Thecracksealingtechniqueisstillevolving,however,anddespiterecentadvances,sealantsoftenMASSON,AdhesionMechanisms,2/16showprematurefailure[3-6].Inmanycases,theexactcauseforsealantfailureremainsunknownandconversely,successfulsealantinstallationcannotberepeatedconsistentlydespiteevidenceforextendedservice-lifeofcracksealants.Bituminouscracksealants,producedwithbitumenmodifiedwithpolymer(s)orcrumbrubber(insomecases,both),willeitherfailadhesivelyorcohesively.Cohesivefailures,characterizedbythefractureofthesealantinthebulk,butstilladheredtothecrackwalls,isuncommonincoldweatherlocations[5,6].Incontrast,theadhesivefailure,adebondingnearthesealant/ACinterfaceismuchmorecommon[5,6],andaswillbeseenlater,itmaysometimesmistakenlybetakenforACfailureinproximitytotheinterface.Studiesonbituminouscracksealantshavebeenmostlyconcernedwithbulkproperties,e.g.[4,7].Manufacturersretainarelativelygoodunderstandingofthesepropertiesandhavebeenabletoimprovetheirphysicalpropertiesovertheyears.Thishasleadtosealantswithgoodcohesion,andthusrarecohesivefailures[5,6].Incontrast,sealantinterfacialpropertieshavenotbeenextensivelystudiedinthecontextofACpavements.ThenatureofadhesionbetweenbituminoussealantsandACisthusstillnotwellunderstood,andtocompensateforthislackofunderstanding,practitionershavetranscribedgeneralknowledgeofadhesivesystemstothesealant/ACsystem.Thistransferofknowledgehasnotbeenperfect,asmightbeexpected,andconsequently,ithasbeendifficultforpractitionerstodesignthestrongestpossiblesealant/ACinterface.Thustheimprovedadhesionthatreducesadhesivefailureandextendtheservicelifeofcracksealantshasbeenelusive.Thelackofattentiongiventointerfacialsealantpropertiespartlystemsfromtheperceptionthatthebulkpropertiescontroladhesion,i.e.,sealantmodulusandstressrelaxationgovernthetensileforcesatthesealant/ACinterface,andadhesiondependsonlyonthemagnitudeoftheseparameters.ThisperceptionsuggeststhatmanypossiblemechanismsforadhesionbetweensealantandAChavenotbeenadequatelyreviewed.Hereweaddresssomeoftheseoversightsandfocusonthecriticalaspectsoftheinterface.Forimprovedclarity,wefirsthighlightworkonsealantbulkproperties,andthen,reviewexistingadhesionmechanismsbasedonathreephasesystem:thesealant,theinterfaceandtheAC.ThisleadstosixpossiblemechanismsforadhesionbetweensealantandAC,andonegeneralrouteforinterfacialfailure.Eachscenarioiscriticallyassessed,completewithfieldandmicroscopicobservationsofACorthesealant/ACinterfacetofurtherelucidatetheconcepts.2.Highlightsofworkonsealantbulkproperties2.1AnalyticalworkEarlyworkbyTons[8]andCastiffetal.[9-11]focusedonthedeterminationofstraininthebulkandatthesurfaceofsealantuponelongationandcompression.Throughacombinationofexperimentalandnumericalwork,theycorrelatedtheeffectofjointwidth,depth,andmovementwithstressthatdevelopinsealants.Itwasalways
本文标题:A Review of Adhesion Mechanisms at the Crack Seala
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