ASTM_C_1399_-_C_1399M_-_10_2015.pdf

Designation:C1399/C1399M10(Reapproved 2015)Standard Test Method forObtaining Average Residual-Strength of Fiber-ReinforcedConcrete1This standard is issued under the fixed designation C1399/C1399M;the number immediately following the designation indicates theyear of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of lastreapproval.A superscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope*1.1 This test method covers the determination of residualstrength of a fiberreinforced concrete test beam.The averageresidual strength is computed using specified beam deflectionsthat are obtained from a beam that has been cracked in astandard manner.The test provides data needed to obtain thatportion of the loaddeflection curve beyond which a significantamount of cracking damage has occurred and it provides ameasure of postcracking strength,as such strength is affectedby the use of fiberreinforcement.1.2 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.1.3 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.2.Referenced Documents2.1 ASTM Standards:2C31/C31M Practice for Making and Curing Concrete TestSpecimens in the FieldC42/C42M Test Method for Obtaining and Testing DrilledCores and Sawed Beams of ConcreteC78 Test Method for Flexural Strength of Concrete(UsingSimple Beam with Third-Point Loading)C172 Practice for Sampling Freshly Mixed ConcreteC192/C192M Practice for Making and Curing Concrete TestSpecimens in the LaboratoryC823 Practice for Examination and Sampling of HardenedConcrete in ConstructionsC1609/C1609M Test Method for Flexural Performance ofFiber-Reinforced Concrete(Using Beam With Third-PointLoading)3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 deflectionmidspan deflection of the test beam ob-tained in a manner that excludes deflection caused by thefollowing:(1)the flexural test apparatus,(2)crushing andseating of the beam at support contact points,and(3)torsion ofthe beam;sometimes termed net deflection.3.1.2 initial loading curvethe loaddeflection curve ob-tained by testing an assembly that includes both the test beamand a specified steel plate(Fig.1);plotted to a deflection of atleast 0.20 mm 0.008 in.(Fig.2).3.1.3 reloading curvethe loaddeflection curve obtainedby reloading and retesting the pre-cracked beam,that is,afterthe initial loading but without the steel plate.(Fig.2)3.1.4 reloading deflectiondeflection measured during thereloading of the cracked beam and with zero deflectionreferenced to the start of the reloading.3.1.5 residual strengththe flexural stress on the crackedbeam section obtained by calculation using loads obtainedfrom the reloading curve at specified deflection values(SeeNote 1).NOTE1Residual strength is not a true stress but an engineering stresscomputed using the flexure formula for linear elastic materials and gross(uncracked)section properties.3.1.6 average residual strengththe average stresscarry-ing ability of the cracked beam that is obtained by calculationusing the residual strength at four specified deflections.4.Summary of Test Method4.1 Cast or sawed beams of fiberreinforced concrete arecracked using the thirdpoint loading apparatus specified inTest Method C78 modified by a steel plate used to assist insupport of the concrete beam during an initial loading cycle(Fig.1).The steel plate is used to help control the rate of1This test method is under the jurisdiction of ASTM Committee C09 onConcrete and Concrete Aggregatesand is the direct responsibility of SubcommitteeC09.42 on Fiber-Reinforced Concrete.Current edition approved July 1,2015.Published September 2015.Originallyapproved in 1998.Last previous edition approved in 2010 as C139910.DOI:10.1520/C1399_C1399M-10R15.2For 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 deflection when the beam cracks.After the beam has beencracked in the specified manner,the steel plate is removed andthe cracked beam is reloaded to obtain data to plot a reloadingloaddeflection curve.Load values at specified deflectionvalues on the reloading curve are averaged and used tocalculate the averag