1、Designation:C 1018 97Standard Test Method forFlexural Toughness and First-Crack Strength ofFiber-Reinforced Concrete(Using Beam WithThird-Point Loading)1This standard is issued under the fixed designation C 1018;the number immediately following the designation indicates the year oforiginal adoption
2、or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method evaluates the flexural performance oftoughness parameters derived
3、from fiber-reinforced concrete interms of areas under the load-deflection curve obtained bytesting a simply supported beam under third-point loading.NOTE1Toughness determined in terms of areas under the load-deflection curve is an indication of the energy absorption capability of theparticular test
4、specimen,and,consequently,its magnitude depends di-rectly on the geometrical characteristics of the test specimen and theloading system.1.2 This test method provides for the determination of anumber of ratios called toughness indices that identify thepattern of material behavior up to the selected d
5、eflectioncriteria.These indices are determined by dividing the areaunder the load-deflection curve up to a specified deflectioncriterion,by the area up to the deflection at which first crack isdeemed to have occurred.Residual strength factors that repre-sent the average post-crack load retained over
6、 a specificdeflection interval as a percentage of the load at first crack arederived from these indices.NOTE2Index values may be increased by preferential alignment offibers parallel to the longitudinal axis of the beam caused by fiber contactwith the mold surfaces or by external vibration.However,i
7、ndex valuesappear to be independent of geometrical specimen and testing variables,such as span length,which do not directly affect fiber alignment.1.3 This test method provides for the determination of thefirst-crack flexural strength using the load corresponding to thepoint on the load-deflection c
8、urve defined in 3.1.1 as firstcrack,and the formula for modulus of rupture given in TestMethod C 78.1.4 Values of flexural toughness and first-crack flexuralstrength stated in inch-pound units are to be regarded as thestandard.Values of toughness indices and residual strengthfactors are independent
9、of the system of units used to measureload and deflection.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
10、 of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:C 31 Practice for Making and Curing Concrete Test Speci-mens in the Field2C 42 Test Method for Obtaining and Testing Drilled Coresand Sawed Beams of Concrete2C 78 Test Method for Flexural Strength of Concrete(UsingSimpl
11、e Beam with Third-Point Loading)2C 172 Practice for Sampling Freshly Mixed Concrete2C 192 Practice for Making and Curing Concrete Test Speci-mens in the Laboratory2C 670 Practice for Preparing Precision and Bias Statementsfor Test Methods for Construction Materials2C 823 Practice for Examination and
12、 Sampling of HardenedConcrete in Constructions23.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 first crackthe point on the load-deflection curve atwhich the form of the curve first becomes nonlinear(approxi-mates the onset of cracking in the concrete matrix).3.1.2 first-crack d
13、eflectionthe deflection value on theload-deflection curve at first crack.3.1.3 first-crack strengththe stress obtained when the loadcorresponding to first crack is inserted in the formula formodulus of rupture given in Test Method C 78.3.1.4 first-crack toughnessthe energy equivalent to thearea unde
14、r the load-deflection curve up to the first-crackdeflection.3.1.5 toughnessthe energy equivalent to the area underthe load-deflection curve up to a specified deflection.3.1.6 toughness indicesthe numbers obtained by dividingthe area up to a specified deflection by the area up to first crack.NOTE3Val
15、ues of 5.0,10.0,and 20.0 for I5,I10,and I20respectively,as defined below,correspond to linear elastic material behavior up to firstcrack and perfectly plastic behavior thereafter(see Appendix X1).1This test method is under the jurisdiction ofASTM Committee C-9 on Concreteand ConcreteAggregates and i
16、s the direct responsibility of Subcommittee C09.42 onFiber-Reinforced Concrete.Current edition approved Dec.10,1997.Published October 1998.Originallypublished as C 1018 84.Last previous edition C 1018 94b.2Annual Book of ASTM Standards,Vol 04.02.1Copyright ASTM,100 Barr Harbor Drive,West Conshohocken,PA 19428-2959,United States.3.1.6.1 toughness index I5the number obtained by divid-ing the area up to a deflection of 3.0 times the first-crackdeflection by the area up to first crack.3.1.6.2 toughn