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SLAGINSIDERThePortCorporationhasextensivelyuseduncrushedblastfurnaceslaginthemajorInnerHarbourdevelopmentprojectswehavecompletedoverthelastdecadeandwewillagainuseintheOuterHarbourprojectsnowunderway.Itsagreatreclamationllmaterialasithasverygoodengineeringproperties.WehavenormallyusedBFslagthathasbeenagedbylongertermstorageinopenstockpiles.ThiseliminatestheproblemsencounteredwithusingfreshBFslagthatcanproduceodours.UsingagedBFslagforreclamationsworksintheharbourasitminimisesthealkalinityofanyleachatethatcomesfromtheslagandinourexperiencepHlevelsofseawateradjacenttothereclamationllfaceareonlyslightlyhigherthanthenaturalpHofseawateritself.ThenaturalangleofreposeofthefaceslopeofBFslagpushedintotheharbourasareclamationisapproximately1.5Hto1Vorabout34degreestothehorizontalwhichisquitesteepandanidealslopeforourharbourrevetmentssotrimmingofthefrontslopeisminimalpriortoplacingrockarmouredrevetmentsonthereclamationfacetoprotectagainstwavedamage.WehaverecentlytestedBFslagattheUniversityofNSWusinglargeshearboxapparatusinordertodeterminetheangleofinternalfrictionoftheslag.Testresultsindicateaof46.Highfrictionanglemeansthatthefactorofsafetyforslopestabilityofthereclamationfaceishighandinthelongtermtheslopeswillremainsecure.Italsoallowsequipmenttoworkclosetoreclamationfacesduringconstruction.TheBFslagcompactsreasonablywellwithunderwaterplacementduetothesurchargeweightofthematerialitself.Deepcompactionhasnotnormallybeenrequiredasthemixedgradingofthematerialaffordsnaturalunderwatercompaction.Oncethereclamationlevelisabovewaterleveltheslagisthencompactedinlayersusingvibratorypadfootrollerswhichbreaksdowntheslagintosmallerparticlesandgreatlyassistscompactionwithveryhighcompactionlevelsachieved.Smoothdrumrollersthensealthesurface.Thismethodproducesanextremelygoodsubgradethatactuallyimprovesitsstrengthovertimewiththehydrationofthecementitiouscomponentsoftheslag.Inportconstructionthepavementsareveryheavydutyduetotheveryhighaxleloadsofstockyardmachinerysuchasforklifttrucksandreachstackers.Ourpavementsaredesignedtoaccommodateaxleloadsof100tonnesandmoreandportpavementsarenormallyinexcessofametrethick.TypicallyonasubgradewithCBRofaround10wewouldhaveasubbaseof300mmaboundbasecourseof600mmandthen150mmofasphalt.WhenweconstructedBerth106anumberofyearsagotheentirereclamationwasofcompactedBFslagandthisproducedasubgradewithaCBR60.DuetothishighCBRwewereabletocompletelyeliminatetheneedforthesubbaselayerandthepavementwasreducedfrom1050mmto775mmthickrealisingaconsiderablecostsaving.IcanhonestlysaythattheportofPortKemblahasbenetedsignicantlyoverthelastfewdecadesbyusingBFslaginportdevelopmentprojectsbothintermsofitsbenecialengineeringpropertiesbutalsobyreducingourdependencyonquarriedproductsbyreusingaby-productoftheironmakingprocessfromthesteelworksjustoverourbackfence.TonileeAndrewsPortEngineerPortKemblaPortCorpINSIDEconnectionswww.asa-inc.org.au04JULY11PortKemblaPortDevelopmentbenetsfromBlastFurnacerockslagpropertiesandavailability