ASTM_C_918_-_C_918M_-_13.pdf

Designation:C918/C918M13Standard Test Method forMeasuring Early-Age Compressive Strength and ProjectingLater-Age Strength1This standard is issued under the fixed designation C918/C918M;the number immediately following the designation indicates the yearof original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.A superscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope*1.1 This test method covers a procedure for making andcuring concrete specimens and for testing them at an early age.The specimens are stored under standard or accelerated curingconditions and the measured temperature history is used tocompute a maturity index that is related to strength gain.1.2 This test method also covers a procedure for using theresults of early-age compressive-strength tests to project thepotential strength of concrete at later ages.1.3 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard.The values stated ineach system may not be exact equivalents;therefore,eachsystem shall be used independently of the other.Combiningvalues from the two systems may result in non-conformancewith the standard.1.4 The text of this standard references notes and footnoteswhich provide explanatory material.These notes and footnotes(excluding those in tables and figures)shall not be consideredas requirements of the standard.1.5 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.(WarningFreshhydraulic cementitious mixtures are caustic and may causechemical burns to skin and tissue upon prolonged exposure.)22.Referenced Documents2.1 ASTM Standards:3C31/C31M Practice for Making and Curing Concrete TestSpecimens in the FieldC39/C39M Test Method for Compressive Strength of Cylin-drical Concrete SpecimensC192/C192M Practice for Making and Curing Concrete TestSpecimens in the LaboratoryC470/C470M Specification for Molds for Forming ConcreteTest Cylinders VerticallyC617/C617M Practice for Capping Cylindrical ConcreteSpecimensC670 Practice for Preparing Precision and Bias Statementsfor Test Methods for Construction MaterialsC1074 Practice for Estimating Concrete Strength by theMaturity MethodC1231/C1231M Practice for Use of Unbonded Caps inDetermination of Compressive Strength of Hardened Con-crete CylindersC1768/C1768M Practice forAccelerated Curing of ConcreteCylinders3.Terminology3.1 Definitions:3.1.1 Refer to Practice C1074 for the definitions of thefollowing terms:datum temperature,equivalent age,maturity,maturity function,maturity index,and temperaturetime factor.3.2 Definitions of Terms Specific to This Standard:3.2.1 potential strength,nthe strength of a test specimenthat would be obtained at a specified age under standard curingconditions.3.2.2 prediction equation,nthe equation representing thestraight-line relationship between compressive strength and thelogarithm of the maturity index.3.2.2.1 DiscussionThe prediction equation is used to proj-ect the strength of a test specimen based upon its measuredearly-age strength.The general form of the prediction equationused in this test method is:SM5 Sm1blog M 2 log m!(1)where:SM=projected strength at maturity index M,Sm=measured compressive strength at maturity index m,b=slope of the line,1This test method is under the jurisdiction of ASTM Committee C09 onConcrete and Concrete Aggregatesand is the direct responsibility of SubcommitteeC09.61 on Testing for Strength.Current edition approved Dec.1,2013.Published January 2014.Originallyapproved in 1980.Last previous edition approved in 2007 as C918 07.DOI:10.1520/C0918_C0918M-13.2Section on Safety Precautions,Manual of Aggregate and Concrete Testing,Annual Book of ASTM Standards,Vol.04.0.2.3For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 M=maturity index under standard curing conditions,andm=maturity index of the specimen tested at early age.The prediction equation is developed by performingcompressive strength tests at various ages,computing thecorresponding maturity indices at the test ages,and plottingthe compressive strength as a function of the logarithm of thematurity index.A best-fit line is drawn through the data andthe slope of this line is used in the prediction equation.3.2.3 projected strength,nthe potential strength estimatedby using the measured early-age strength and the previouslyestablished prediction eq