ASTM C457-2008

Designation:C457–08StandardTestMethodforMicroscopicalDeterminationofParametersoftheAir-VoidSysteminHardenedConcrete1ThisstandardisissuedunderthefixeddesignationC457;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(e)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope*1.1Thistestmethoddescribesproceduresformicroscopicaldeterminationsoftheaircontentofhardenedconcreteandofthespecificsurface,voidfrequency,spacingfactor,andpaste-airratiooftheair-voidsysteminhardenedconcrete(1).2Twoproceduresaredescribed:1.1.1ProcedureA,thelinear-traversemethod(2,3).1.1.2ProcedureB,themodifiedpoint-countmethod(3,4,5,6).1.2Thistestmethodisbasedonprescribedproceduresthatareappliedtosawedandlappedsectionsofspecimensofconcretefromthefieldorlaboratory.1.3Itisintendedtooutlinetheprinciplesofthistestmethodandtoestablishstandardsforitsadequateperformancebutnottodescribeindetailallthepossiblevariationsthatmightbeusedtoaccomplishtheobjectivesofthistestmethod.1.4ThevaluesstatedinSIunitsaretoberegardedasthestandard.Thevaluesinparenthesesareprovidedforinforma-tionpurposesonly.1.5Thisstandarddoesnotpurporttoaddressallofthesafetyconcernsassociatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappropriatesafetyandhealthpracticesanddeterminetheapplicabilityofregulatorylimitationspriortouse.Forspecifichazardstatementssee8.3and10.1.2.ReferencedDocuments2.1ASTMStandards:3C42/C42MTestMethodforObtainingandTestingDrilledCoresandSawedBeamsofConcreteC138/C138MTestMethodforDensity(UnitWeight),Yield,andAirContent(Gravimetric)ofConcreteC173/C173MTestMethodforAirContentofFreshlyMixedConcretebytheVolumetricMethodC231TestMethodforAirContentofFreshlyMixedConcretebythePressureMethodC670PracticeforPreparingPrecisionandBiasStatementsforTestMethodsforConstructionMaterialsC823PracticeforExaminationandSamplingofHardenedConcreteinConstructionsC856PracticeforPetrographicExaminationofHardenedConcreteD92TestMethodforFlashandFirePointsbyClevelandOpenCupTester2.2AmericanConcreteInstituteStandards:201.2RGuidetoDurableConcrete4211.1RecommendedPracticeforSelectingProportionsforNormal,Heavyweight,andMassConcrete43.Terminology3.1Definitions:3.1.1aircontent(A)—Theproportionofthetotalvolumeoftheconcretethatisairvoids;expressedaspercentagebyvolume.3.1.2airvoid—Aspaceenclosedbythecementpasteandthatwasfilledwithairorothergaspriortothesettingofthepaste.3.1.2.1Discussion—Thistermdoesnotrefertovoidsofsubmicroscopicaldimensions,suchastheporosityinherenttothehardened-cementpaste.Airvoidsareusuallylargerthanafewmicrometersindiameter.Thetermincludesbothentrappedandentrainedvoids.3.1.3averagechordlength(l)—Theaveragelengthofthechordsformedbythetransectionofthevoidsbythelineoftraverse;theunitisalength.3.1.4paste-airratio(p/A)—Theratioofthevolumeofhardenedcementpastetothevolumeoftheairvoidsintheconcrete.1ThistestmethodisunderthejurisdictionofASTMCommitteeC09onConcreteandConcreteAggregatesandisthedirectresponsibilityofSubcommitteeC09.65onPetrography.CurrenteditionapprovedJan.1,2008.PublishedJanuary2008.Originallyapprovedin1960.Lastpreviouseditionapprovedin2006asC457–06.2Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendofthistestmethod.3ForreferencedASTMstandards,visittheASTMwebsite,@astm.org.ForAnnualBookofASTMStandardsvolumeinformation,refertothestandard’sDocumentSummarypageontheASTMwebsite.4AvailablefromAmericanConcreteInstitute(ACI),P.O.Box9094,FarmingtonHills,MI48333-9094,*ASummaryofChangessectionappearsattheendofthisstandard.Copyright©ASTMInternational,100BarrHarborDrive,POBoxC700,WestConshohocken,PA19428-2959,UnitedStates.3.1.5pastecontent(p)—Theproportionofthetotalvolumeoftheconcretethatishardenedcementpasteexpressedaspercentagebyvolume.3.1.5.1Discussion—Whenthisparameteriscalculated,itisthesumoftheproportionalvolumesofthecement,thenetmixingwater(includingtheliquidportionsofanychemicaladmixtures),andanymineraladmixturespresent(7,8).3.1.6spacingfactor(L)—Aparameterrelatedtothemaximumdistanceinthecementpastefromtheperipheryofanairvoid,theunitisalength.3.1.7specificsurface(a)—Thesurfaceareaoftheairvoidsdividedbytheirvolume,expressedincompatibleunitssothattheunitofspecificsurfaceisareciprocallength.3.1.8voidfrequency,n—Voidsperunitlengthoftraverse;thenumberofairvoidsinterceptedbyatraverselinedividedbythelengthofthatline;theunitisareciprocallength.3.1.8.1Discussion—Thevalueforvoidfrequency(n)can-notbedirectlydeterminedbythepaste-airratiomethodasthisvaluereferstothevoidsperunitmeasureoftraverseinthetotalconcrete(includingaggregate).3.1.9watervoid—Aspaceenclosedbythecementpastethatwasoccupiedbywateratthetimeofsettingandfrequentlyfoundunderanaggregateparticleorreinforcingbar.Awater-voidisusuallyidentifiedbyitsirregularshapeorevidencethatachannelorcavityhasbeencreatedbybleedwatertrappedintheconcreteatthetimeithardened.4.SummaryofTestMethod4