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1、AbituminoussurfacetreatmentAbituminoussurfacetreatment(BST),alsoknownasasealcoatorchipseal,isathinprotectivewearingsurfacethatisappliedtoapavementorbasecourse.BSTscanprovideallofthefollowing:Awaterprooflayertoprotecttheunderlyingpavement.Increasedskidresistance.
2、Afillerforexistingcracksorraveledsurfaces.Ananti-glaresurfaceduringwetweatherandanincreasedreflectivesurfacefornightdriving.Historically,BSTshavebeeninusesincethe1920s,primarilyonlowvolumegravelroads.BSTsareincreasinglyinuseasapreventativemaintenanceprocedureonf
3、lexiblepavementsofgoodstructure.PurposeABSTofferspreventivemaintenancefromtheeffectsofsunandwater,bothofwhichmaydeterioratethepavementstructure.BSTscreateanewwearingcourse,aswellasawaterproofcoveringfortheexistingpavement.ABSTmakesitmoredifficultforwatertoentert
4、hebasematerial,andpreventingfreezethawdamageforthoselocationswithbelowfreezingtemperatures.BSTsalsoincreasethesurfacefrictionofthepavement,duetotheadditionofthecoveraggregate.Thiscombatstheeffectsofraveling,whichcanmakethepavementslipperyandstoppingdifficult.ABS
5、Tgivesgood,grippingtexturetothepavementsurface.BSTsshouldbeappliedtoadistress-freetomoderatelydistressedpavementsurface.Atwotofouryearservicelifeiscommon,whilefiveyearservicelivesareachievable.MaterialsBSTsarecreatedusingtwomainmaterials:asphaltandacoveraggregat
6、e.AsphaltAsphalt(asasphaltbinder,cutbackasphaltorasphaltemulsion)andaggregate(uniformlygraded).Theasphaltistypicallyanemulsion.Caremustbetakenwiththeweatheronthedayofconstruction–ideally,awarmdaywithlowhumidityispreferred.BSTsshouldneverbeconstructedonrainydayso
7、rwhenrainispredicted.Raincandilutetheasphaltbinderifithasnotyetcured,bringingthebindertothetopofthecoveraggregate;afterthewaterevaporates,tirescanpickupthelooseaggregateortrackbinderacrossthesurface.CutbackAsphaltWhilecutbackasphaltishistoricallyanoptionforBSTs,
8、thesolventused(usuallygasolineorkerosene)isexpensiveandpotentiallydangerous.Acutbackisasphaltdissolvedinasolvent,allowingtheasphalttobepumpedandsprayedwithoutheatingi
