ASTM-C78

Designation:C78/C78M–10StandardTestMethodforFlexuralStrengthofConcrete(UsingSimpleBeamwithThird-PointLoading)1ThisstandardisissuedunderthefixeddesignationC78/C78M;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.ThisstandardhasbeenapprovedforusebyagenciesoftheDepartmentofDefense.1.Scope*1.1Thistestmethodcoversthedeterminationoftheflexuralstrengthofconcretebytheuseofasimplebeamwiththird-pointloading.1.2ThevaluesstatedineitherSIunitsorinch-poundunitsaretoberegardedseparatelyasstandard.Thevaluesstatedineachsystemmaynotbeexactequivalents;therefore,eachsystemshallbeusedindependentlyoftheother.Combiningvaluesfromthetwosystemsmayresultinnon-conformancewiththestandard.1.3Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.2.ReferencedDocuments2.1ASTMStandards:2C31/C31MPracticeforMakingandCuringConcreteTestSpecimensintheFieldC42/C42MTestMethodforObtainingandTestingDrilledCoresandSawedBeamsofConcreteC192/C192MPracticeforMakingandCuringConcreteTestSpecimensintheLaboratoryC617PracticeforCappingCylindricalConcreteSpecimensC1077PracticeforLaboratoriesTestingConcreteandCon-creteAggregatesforUseinConstructionandCriteriaforLaboratoryEvaluationE4PracticesforForceVerificationofTestingMachines3.SignificanceandUse3.1ThistestmethodisusedtodeterminetheflexuralstrengthofspecimenspreparedandcuredinaccordancewithTestMethodsC42/C42MorPracticesC31/C31MorC192/C192M.Resultsarecalculatedandreportedasthemodulusofrupture.Thestrengthdeterminedwillvarywheretherearedifferencesinspecimensize,preparation,moisturecondition,curing,orwherethebeamhasbeenmoldedorsawedtosize.3.2Theresultsofthistestmethodmaybeusedtodeterminecompliancewithspecificationsorasabasisforproportioning,mixingandplacementoperations.Itisusedintestingconcretefortheconstructionofslabsandpavements.4.Apparatus4.1ThetestingmachineshallconformtotherequirementsofthesectionsonBasisofVerification,Corrections,andTimeIntervalBetweenVerificationsofPracticesE4.Handoperatedtestingmachineshavingpumpsthatdonotprovideacontinu-ousloadinginonestrokearenotpermitted.Motorizedpumpsorhandoperatedpositivedisplacementpumpshavingsuffi-cientvolumeinonecontinuousstroketocompleteatestwithoutrequiringreplenishmentarepermittedandshallbecapableofapplyingloadsatauniformratewithoutshockorinterruption.4.2LoadingApparatus—Thethirdpointloadingmethodshallbeusedinmakingflexuretestsofconcreteemployingbearingblocksthatwillensurethatforcesappliedtothebeamwillbeperpendiculartothefaceofthespecimenandappliedwithouteccentricity.Adiagramofanapparatusthataccom-plishesthispurposeisshowninFig.1.4.2.1Allapparatusformakingflexuretestsofconcreteshallbecapableofmaintainingthespecifiedspanlengthanddistancesbetweenload-applyingblocksandsupportblocksconstantwithin61.0mm[60.05in.].4.2.2Theratioofthehorizontaldistancebetweenthepointofapplicationoftheloadandthepointofapplicationofthenearestreactiontothedepthofthebeamshallbe1.060.03.1ThistestmethodisunderthejurisdictionofASTMCommitteeC09onConcreteandConcreteAggregatesandisthedirectresponsibilityofSubcommitteeC09.61onTestingforStrength.CurrenteditionapprovedAug.1,2010.PublishedSeptember2010.Originallyapprovedin1930.Lastpreviouseditionapprovedin2009asC78–09.DOI:10.1520/C0078_C0078M-10.2ForreferencedASTMstandards,visittheASTMwebsite,@astm.org.ForAnnualBookofASTMStandardsvolumeinformation,refertothestandard’sDocumentSummarypageontheASTMwebsite.1*ASummaryofChangessectionappearsattheendofthisstandard.Copyright©ASTMInternational,100BarrHarborDrive,POBoxC700,WestConshohocken,PA19428-2959,UnitedStates.CopyrightASTMInternationalProvidedbyIHSunderlicensewithASTMLicensee=UniversityofTennessee/5622000001NotforResale,11/22/201213:27:50MSTNoreproductionornetworkingpermittedwithoutlicensefromIHS--``,,,,`,,,```,,,,,``,,`,,``,`,-`-`,,`,,`,`,,`---4.2.3IfanapparatussimilartothatillustratedinFig.1isused:theload-applyingandsupportblocksshallnotbemorethan65mm[2.50in.]high,measuredfromthecenterortheaxisofpivot,andshouldextendentirelyacrossorbeyondthefullwidthofthespecimen.Eachcase-hardenedbearingsurfaceincontactwiththespecimenshallnotdepartfromaplanebymorethan0.05mm[0.002in.]andshallbeaportionofacylinder,theaxisofwhichiscoincidentalwitheithertheaxisoftherodorcenteroftheball,whichevertheblockispivotedupon.Theanglesubtendedbythecurvedsurfaceofeachblockshallbeatleast0.80rad[45°].Theload-applyingandsupportblocksshallbemaintainedinaverticalpositionandincontactwiththerodorballbymeansofspring-loadedscrewsthatholdthemincontactwiththepivotrodorball.TheuppermostbearingplateandcenterpointballinFig.1maybeomittedwhenasphericallyseatedbearingblockisused,providedonerodandoneballareusedaspivotsfortheup