Designation:C138/C138M−17aAmericanAssociationStateHighwayandTransportationOfficialsStandardAASHTONo.:T121StandardTestMethodforDensity(UnitWeight),Yield,andAirContent(Gravimetric)ofConcrete1ThisstandardisissuedunderthefixeddesignationC138/C138M;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.ThisstandardhasbeenapprovedforusebyagenciesoftheU.S.DepartmentofDefense.1.Scope*1.1Thistestmethodcoversdeterminationofthedensity(seeNote1)offreshlymixedconcreteandgivesformulasforcalculatingtheyield,cementcontent,andaircontentoftheconcrete.Yieldisdefinedasthevolumeofconcreteproducedfromamixtureofknownquantitiesofthecomponentmateri-als.1.2ThevaluesstatedineitherSIunitsorinch-poundunitsaretoberegardedseparatelyasstandard.Thevaluesstatedineachsystemmaynotbeexactequivalents;therefore,eachsystemshallbeusedindependentlyoftheother.Combiningvaluesfromthetwosystemsmayresultinnon-conformancewiththestandard.NOTE1—Unitweightwasthepreviousterminologyusedtodescribethepropertydeterminedbythistestmethod,whichismassperunitvolume.1.3Thetextofthistestmethodreferencesnotesandfootnotesthatprovideexplanatoryinformation.Thesenotesandfootnotes(excludingthoseintables)shallnotbeconsid-eredasrequirementsofthistestmethod.1.4Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.(Warning—Freshhydrauliccementitiousmixturesarecausticandmaycausechemicalburnstoskinandtissueuponprolongedexposure.2)1.5Thisinternationalstandardwasdevelopedinaccor-dancewithinternationallyrecognizedprinciplesonstandard-izationestablishedintheDecisiononPrinciplesfortheDevelopmentofInternationalStandards,GuidesandRecom-mendationsissuedbytheWorl...
