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www.asa-inc.org.auAPRIL1105TheregenerativefrictionalpropertiesofslagaggregatePolishingStageWeatheringStageConclusionNickJones-HarscoMetalsGroupLimitedconnectionsIthasbeenacceptedbymanyroadauthoritiesintheUKthatsteelslagasphalthasprovidedagoodlevelofskidresistancethroughoutthelifeofthesurfacing.LongtermmonitoringofthefrictionalpropertiesofthesematerialsusingSCRIMSide-waysForceRoutineInvestigatoryMachineandGriptestinghassupportedthisprovidingvaluesabovetheminimuminvestigatorylevelwithoutanysignicantdropinperformance.InanattempttogainabetterunderstandingofthisphenomenontheUniversityofUlsteraleadingauthorityonroadstoneinteractionwascommissionedbyHarscoMetalstoinvestigateavarietyofironandsteelmakingslagsfromHarscositesaroundtheworld.ThisiscomprisedoftwoEAFslagsfromtheUKandonefromAustraliaoneBOSslagfromTheNetherlandsonestabilisedAODstainlessslagfromtheUKandoneMelterironslagfromNewZealand.Thetestingprotocolinvolvedaseriesofstandardteststoevaluatethegeneralphysicalandmechanicalpropertiesoftheslagaggregatesinordertocomparethemwithsimilarqualityaggregatesontheuniversitydatabase.TheresultsofthisstageoftestingconcludedthatalltheslagswereequivalenttothenaturalaggregatesontheuniversitiesdatabaseofapprovedmaterialsforsurfacecoursematerialsintheUK.HoweveralltheslagsprovedtobemoreresistanttofragmentationthannaturalaggregatesandtheresistancetowearunderbothwetanddryconditionswasfoundtobemuchbetterthanthemajorityofhigherPSVpolishedstonevalueaggregatesusedintheUK.Thenextstageoftestingconsistedofaseriesofnon-standardtestsdesignedtosubjecttheaggregatetoextremestressinrelationtopolishingbutalsotoassesstheeffectofenvironmentalconditionsassociatedwithnaturalweatheringi.e.rainfallanddryspellsetc.Threepolishingregimeswerecarriedoutonstandard610mmsamplesofalltheslagtypesusedfortheproject.Thesetooktheformofextendedpolishingtimeandalsoaggressivesidewayspolishingwithanoffsetwheelatsixty60.Thedatashowseachslagtohavelostbetween17to27ofitsunpolishedskidresistanceduringthestandardsix6hourPSVtest.Extendedpolishingwasfoundtofurtherreduceskidresistancebybetween5to12.Theresultsoftheadditionalperiodofintensestressingreducedthevaluestobetween52to65ofthestandardPSV.Allslagsperformeddifferentlytoeachotherbutalsounderdifferentpolishingregimes.Threeregimesofvaryingdegreesofwettinganddryingwereusedforthisstageoftests.RepeatedwettinganddryingresultedinallslagtypesrecoveringskidresistancevaluesabovethestandardPSVafterextendedpolishing.AODshowedadramaticrecoveryofaround70abovethestandardPSV.Airdryingprovidedalesserrecoveryofbetween12and22ofthestandardPSV.Evenaftertheextendedaggressivepolishingtheslagsskidresistancevaluerecoveredtobetween68and87ofthestandardPSV.Furthersoakingshowedthattheslagsrecoveredanaverageof97ofthestandardPSV.Allsix6samplesofslagrecoveredwetskidresistanceinall3postpolishingregimesandthetrendcontinuedupwardsattheendofalltestregimes.Thisdoesnothappenwithnaturalaggregates.Theresultofthisstudydemonstratesthelowabrasionandprolongedskidresistanceofsteelmakingslagaggregatesthusimprovingthesafetyofroadsforlongerandprolongingthelifeoftheroadensuringcosteffectivesolutionsforthehighwayauthorities.