1、Designation: C 1609/C 1609M 06Standard Test Method forFlexural Performance of Fiber-Reinforced Concrete (UsingBeam With Third-Point Loading)1This standard is issued under the fixed designation C 1609/C 1609M; the number immediately following the designation indicates theyear of original adoption or,
2、 in the case of revision, the year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method evaluates the flexural performance offiber-reinforced concret
3、e using parameters derived from theload-deflection curve obtained by testing a simply supportedbeam under third-point loading using a closed-loop, servo-controlled testing system.1.2 This test method provides for the determination offirst-peak and peak loads and the corresponding stressescalculated
4、by inserting them in the formula for modulus ofrupture given in Eq 1. It also requires determination of residualloads at specified deflections, and the corresponding residualstrengths calculated by inserting them in the formula formodulus of rupture given in Eq 1 (see Note 1). At the option ofthe sp
5、ecifier of tests, it provides for determination of specimentoughness based on the area under the load-deflection curve upto a prescribed deflection (see Note 2).NOTE 1Residual strength is not a true stress but an engineering stresscomputed using simple engineering bending theory for linear elasticma
6、terials and gross (uncracked) section properties.NOTE 2Specimen toughness expressed in terms of the area under theload-deflection curve is an indication of the energy absorption capabilityof the particular test specimen, and its magnitude depends directly on thegeometry of the test specimen and the
7、loading configuration.1.3 This test method utilizes two preferred specimen sizesof 100 by 100 by 350 mm (4 by 4 by 14 in.) tested on a 300 mm(12 in.) span, or 150 by 150 by 500 mm (6 by 6 by 20 in.)tested on a 450 mm (18 in.) span. A specimen size differentfrom the two preferred specimen sizes is pe
8、rmissible.1.4 UnitsThe values stated in either SI units or inch-pound units are to be regarded separately as standard. Thevalues stated in each system may not be exact equivalents;therefore, each system shall be used independently of the other.Combining values from the two systems may result in non-
9、conformance with 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 limitation
10、s prior to use.2. Referenced Documents2.1 ASTM Standards:2C 31/C 31M Practice for Making and Curing Concrete TestSpecimens in the FieldC 42/C 42M Test Method for Obtaining and Testing DrilledCores and Sawed Beams of ConcreteC78 Test Method for Flexural Strength of Concrete (UsingSimple Beam with Thi
11、rd-Point Loading)C 125 Terminology Relating to Concrete and ConcreteAggregatesC 172 Practice for Sampling Freshly Mixed ConcreteC 192/C 192M Practice for Making and Curing ConcreteTest Specimens in the LaboratoryC 823 Practice for Examination and Sampling of HardenedConcrete in ConstructionsC 1140 P
12、ractice for Preparing and Testing Specimens fromShotcrete Test Panels3. Terminology3.1 DefinitionsThe terms used in this test method aredefined in Terminology C 125.3.2 Definitions of Terms Specific to This Standard:3.2.1 end-point deflectionthe deflection value on the load-deflection curve equal to
13、1150 of the span, or a larger value asspecified at the option of the specifier of tests.3.2.2 first-peak load, P1the load value at the first point onthe load-deflection curve where the slope is zero.3.2.3 first-peak deflection, d1the net deflection value onthe load-deflection curve at first-peak loa
14、d.3.2.4 first-peak strength f1the stress value obtained whenthe first-peak load is inserted in the formula for modulus ofrupture given in Eq 1.3.2.5 load-deflection curvethe plot of load versus netdeflection of a flexural beam specimen loaded to the end-pointdeflection.1This test method is under the
15、 jurisdiction of ASTM Committee C09 onConcrete and Concrete Aggregates and is the direct responsibility of SubcommitteeC09.42 on Fiber-Reinforced Concrete.Current edition approved Dec. 15, 2006. Published January 2007. Originallyapproved in 2005. Last previous edition approved in 2005 as C 1609/C 16
16、09M 05.2For 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.1*A Summary of Changes section appears at the end of t
17、his standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.6 net deflectionthe deflection measured at mid-span ofa flexural beam specimen exclusive of any extraneous effectsdue to seating or twisting of the specimen on its suppo
18、rts ordeformation of the support and loading system.3.2.7 peak load, PPthe maximum load on the load-deflection curve.3.2.8 peak-load deflection, dPthe net deflection value onthe load-deflection curve at peak load.3.2.9 peak strength, fPthe stress value obtained when thepeak load is inserted in the f
19、ormula for modulus of rupturegiven by Eq 1.3.2.10 residual load, P150,0.75the load value correspond-ing to a net deflection equal to1600 of the span (or 0.75mm0.03 in.) using a specimen with a depth of 150 mm (6 in.).3.2.11 residual load, P100,0.50the load value correspond-ing to a net deflection eq
20、ual to1600 of the span (or 0.50mm0.02 in.) using a specimen with a depth of 100 mm (4 in.).3.2.12 residual load, P150,3.0the load value correspondingto a net deflection equal to1150 of the span (3.0 mm0.12 in.)using a specimen with a depth of 150 mm (6 in.).3.2.13 residual load, P100,2.0the load val
21、ue correspondingto a net deflection equal to1150 of the span (2.0 mm0.08 in.)using a specimen with a depth of 100 mm (4 in.).3.2.14 residual strength, f150,0.75the stress value obtainedwhen the residual load P150,0.75is inserted in the formula formodulus of rupture given in Eq 1.3.2.15 residual stre
22、ngth, f100,0.50the stress value obtainedwhen the residual load P100,0.50is inserted in the formula formodulus of rupture given in Eq 1.3.2.16 residual strength, f150,3.0the stress value obtainedwhen the residual load P150,3.0is inserted in the formula formodulus of rupture given in Eq 1.3.2.17 resid
23、ual strength, f100,2.0the stress value obtainedwhen the residual load P100,2.0is inserted in the formula formodulus of rupture given in Eq 1.3.2.18 specimen toughness, T150,3.0the energy equivalentto the area under the load-deflection curve up to a net deflectionof1150 of the span (3.0 mm0.12 in.) u
24、sing a specimen with adepth of 150 mm (6 in.).3.2.19 specimen toughness, T100,2.0the energy equivalentto the area under the load-deflection curve up to a net deflectionof1150 of the span (2.0 mm0.08 in.) using a specimen with adepth of 100 mm (4 in.).4. Summary of Test Method4.1 Molded or sawn beam
25、specimens having a squarecross-section of fiber-reinforced concrete are tested in flexureusing a third-point loading arrangement similar to that speci-fied in Test Method C78 but incorporating a closed-loop,servo-controlled testing system and roller supports that are freeto rotate on their axes. Loa
26、d and net deflection are monitoredand recorded to an end-point deflection of at least1150 of thespan. Data are recorded and plotted by means of an X-Yplotter, or they are recorded digitally and subsequently used toplot a load-deflection curve. Points termed first-peak, peak, andresidual loads at spe
27、cified deflections are identified on thecurve, and are used to calculate flexural performance param-eters.5. Significance and Use5.1 The first-peak strength characterizes the flexural behav-ior of the fiber-reinforced concrete up to the onset of cracking,while residual strengths at specified deflect
28、ions characterize theresidual capacity after cracking. Specimen toughness is ameasure of the energy absorption capacity of the test specimen.The appropriateness of each parameter depends on the natureof the proposed application and the level of acceptable crack-ing and deflection serviceability. Fib
29、er-reinforced concrete isinfluenced in different ways by the amount and type of fibers inthe concrete. In some cases, fibers may increase the residualload and toughness capacity at specified deflections whileproducing a first-peak strength equal to or only slightly greaterthan the flexural strength
30、of the concrete without fibers. Inother cases, fibers may significantly increase the first-peak andpeak strengths while affecting a relatively small increase inresidual load capacity and specimen toughness at specifieddeflections.5.2 The first-peak strength, peak strength, and residualstrengths dete
31、rmined by this test method reflect the behavior offiber-reinforced concrete under static flexural loading. Theabsolute values of energy absorption obtained in this test are oflittle direct relevance to the performance of fiber-reinforcedconcrete structures since they depend directly on the size ands
32、hape of the specimen and the loading arrangement.5.3 The results of this test method may be used for com-paring the performance of various fiber-reinforced concretemixtures or in research and development work. They may alsobe used to monitor concrete quality, to verify compliance withconstruction sp
33、ecifications, obtain flexural strength data onfiber-reinforced concrete members subject to pure bending, orto evaluate the quality of concrete in service.5.4 The results of this standard test method are dependenton the size of the specimen.NOTE 3The results obtained using one size molded specimen ma
34、y notcorrespond to the performance of larger or smaller molded specimens,concrete in large structural units, or specimens sawn from such units. Thisdifference may occur because the degree of preferential fiber alignmentbecomes more pronounced in molded specimens containing fibers that arerelatively
35、long compared with the cross-sectional dimensions of the mold.Moreover, structural members of significantly different thickness experi-ence different maximum crack widths for a given mid-span deflection withthe result that fibers undergo different degrees of pull-out and extension.6. Apparatus6.1 Te
36、sting MachineThe testing machine shall be capableof servo-controlled operation where the net deflection of thecenter of the beam is measured and used to control the rate ofincrease of deflection. Testing machines that use stroke dis-placement control or load control are not suitable for estab-lishin
37、g the portion of the load-deflection curve immediatelyafter first-peak. The loading and specimen support system shallbe capable of applying third-point loading to the specimenwithout eccentricity or torque. The fixtures specified in TestMethod C78are suitable with the qualification that supportingro
38、llers shall be able to rotate on their axes and shall not beplaced in grooves or have other restraints that prevent their freerotation.C 1609/C 1609M 0626.2 Deflection-Measuring EquipmentDevices such aselectronic transducers or electronic deflection gages shall belocated in a manner that ensures acc
39、urate determination of thenet deflection at the mid-span exclusive of the effects of seatingor twisting of the specimen on its supports. One acceptablearrangement employs a rectangular jig, which surrounds thespecimen and is clamped to it at mid-depth directly over thesupports (Figs. 1 and 2). Two e
40、lectronic displacement trans-ducers or similar digital or analog devices mounted on the jigat mid-span, one on each side, measure deflection throughcontact with appropriate brackets attached to the specimen.The average of the measurements represents the net deflection.6.3 Data Recording SystemAn X-Y
41、 plotter coupled di-rectly to electronic outputs of load and deflection is anacceptable means of obtaining the relationship between loadand net deflectionthat is, the load-deflection curve. A dataacquisition system capable of digitally recording and storingload and deflection data at a sampling freq
42、uency of at least 2.5Hz is an acceptable alternative. After a net deflection of L/600has been exceeded, it is permissible to decrease the dataacquisition sampling and recording frequency to 1 Hz.NOTE 4For X-Y plotters, accurate determination of the area under theload-deflection curve and the loads c
43、orresponding to specified deflectionsis only possible when the scales chosen for load and deflection arereasonably large. A load scale chosen such that 25 mm (1 in.) correspondsto a flexural stress of the order of 1 MPa (150 psi), or no more than 20 %of the estimated first-peak strength, is recommen
44、ded. A recommendeddeflection scale is to use 25 mm (1 in.) to represent about 10 % of theend-point deflection of1150 of the span, which is 2 mm (0.08 in.) for a 350by 100 by 100 mm (14 by 4 by 4 in.) specimen size, and 3 mm (0.12 in.)for a 500 by 150 by 150 mm (20 by 6 by 6 in.) specimen size. When
45、dataare digitally stored, the test parameters may be determined directly fromthe stored data or from a plot of the data. In the latter case, use a plot scalesimilar to that recommended for an X-Y plotter.7. Sampling, Test Specimens, and Test Units7.1 General RequirementsThe nominal maximum size ofag
46、gregate and cross-sectional dimensions of test specimensshall be in accordance with Practice C 31/C 31M or PracticeC 192/C 192M when using molded specimens, or in accor-dance with Test Method C 42/C 42M when using sawn speci-mens, provided that the following requirements are satisfied:7.1.1 The leng
47、th of test specimens shall be at least 50 mm (2in.) greater than three times the depth, and in any case not lessthan 350 mm (14 in.). The length of the test specimen shall notbe more than two times the depth greater than the span.7.1.2 The tolerances on the cross-section of the test speci-mens shall
48、 be within 6 2 %. The test specimens shall have asquare cross-section within these tolerances.7.1.3 The width and depth of test specimens shall be at leastthree times the maximum fiber length.7.1.4 When the specimen size is not large enough to meet allthe requirements of 7.1-7.1.3, specimens of squa
49、re cross-section large enough to meet the requirements shall be used.The three times maximum fiber length requirement for widthand depth may be waived at the option of the specifier of teststo permit specimens with a width and depth of 150 mm (6 in.)when using fibers of length 50 to 75 mm (2 to 3 in.).NOTE 5The results of tests on beams with relatively stiff fibers, suchas steel fibers, longer than one-third the width and depth of the beam maynot be comparable with test results of similar-sized beams with fibersshorter than one-third the
