1、Designation: C1399/C1399M 10Standard 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, t
2、he 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
3、 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 provi
4、des ameasure of postcracking strength, as such strength is affectedby the use of fiberreinforcement.1.2 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 heal
5、th practices and determine the applica-bility of regulatory limitations prior to use.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
6、of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.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 Concr
7、eteC78 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 ConcreteTest Specimens in the LaboratoryC823 Practice for Examination and Sampling of HardenedConcrete in Constru
8、ctionsC1609/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 thefol
9、lowing: (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 ste
10、el 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
11、 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).NOTE 1Residu
12、al 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 s
13、trength 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 cycle1Thi
14、s test method is under the jurisdiction of ASTM Committee C09 onConcrete and Concrete Aggregates and is the direct responsibility of SubcommitteeC09.42 on Fiber-Reinforced Concrete.Current edition approved Jan. 1, 2010. Published February 2010. Originallyapproved in 1998. Last previous edition appro
15、ved in 2007 as C139907a. DOI:10.1520/C1399_C1399M-10.2For 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 Summ
16、ary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.(Fig. 1). The steel plate is used to help control the rate ofdeflection when the beam cracks. After the beam has beencracked in
17、 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 average residual strength of the beam.5. Significance and U
18、se5.1 This test method provides a quantitative measure usefulin the evaluation of the performance of fiberreinforcedconcrete. It allows for comparative analysis among beamscontaining different fiber types, including materials, dimensionand shape, and different fiber contents. Results can be used too
19、ptimize the proportions of fiberreinforced concrete mixtures,to determine compliance with construction specifications, toevaluate fiberreinforced concrete which has been in service,and as a tool for research and development of fiberreinforcedconcrete (See Note 2).NOTE 2Banthia and Dubey3compared res
20、ults using this test methodwith residual strengths at the same net deflections using a test protocol thatis similar to that described in Test Method C1609/C1609M on 45 beamswith a single fiber configuration at proportions of 0.1, 0.3, and 0.5 % byvolume. The results by this test method were on avera
21、ge 6.4 % lower thanby the procedure of Test Method C1609/C1609M.5.2 Test results are intended to reflect either consistency ordifferences among variables used in proportioning the fiber-reinforced concrete to be tested, including fiber type (mate-rial), fiber size and shape, fiber amount, beam prepa
22、ration(sawed or molded), and beam conditioning.5.3 In molded beams fiber orientation near molded surfaceswill be affected by the process of molding. For tests offiber-reinforced concrete containing relatively rigid or stifffibers of length greater than 35 mm 1.4 in., the use of sawedbeams cut from s
23、amples with an initial width and depth of atleast 3 times the length of the fiber is required to minimizeeffects of fiber orientation. When sawed beams are employed,and to avoid the effects of fiber orientation, care shall beapplied to ensure that the flexural tensile surface of the beam isa sawed s
24、urface.6. Apparatus6.1 Either Screw Gear or Hydraulic Testing Apparatus, withthe ability to control the rate of motion of the loading head andmeeting the requirements of Test Method C78. A load cell witha 44.5 kN capacity 10,000 lbf will generally be required.Closed-loop feed-back controlled deflect
25、ion apparatus is notrequired.6.2 Flexural-Loading Beam-Support Apparatus, conform-ing to the requirements of Test Method C78.6.3 Load and DeflectionMeasuring Devices, such as loadcells and electronic transducers, capable of producing elec-tronic analog signals and having support apparatus located an
26、darranged in a manner that provides determination of appliedload and mid-span deflection (See 3.1.5) of the beam. Measure3Banthia, N. and Dubey, A., “Measurement of Flexural Toughness of FiberReinforced Concrete Using a Novel Technique, Part I:Assessment and Calibration,”In Press, Materials Journal,
27、 American Concrete Institute.FIG. 1 Schematic of a Suitable Apparatus Where the Deflection Gauge Support Frame is Seated on the BeamC1399/C1399M 102deflection using a device capable of measuring net deflection atthe beam midspan with a minimum resolution of 0.025 mm0.001 in. by one of the following
28、alternative methods.NOTE 3The deflection measurement requires care in the arrangementof displacement transducers in order to minimize extraneous contributionssuch as might be caused by seating or twisting of the specimen.Experience has shown that apparatus designed to support deflectionmeasuring dev
29、ices that eliminate extraneous deflections is acceptable.Methods to accomplish this measurement use spring-loaded electronicdisplacement transducers mounted on suspension frames or supportframes as shown in Fig. 1.6.3.1 Three Electronic Transducers, mounted on a supportframe. The support frame posit
30、ions the transducers along thecenterline of the top surface of the test beam at locations so asto contact the beam at mid-span and each support location.Average the measured support deflections and subtract thisvalue from the recorded mid-span deflection to obtain the netdeflection.6.3.2 Two Electro
31、nic Transducers, mounted on a supportframe. The support frame either (1) surrounds the test beamand is clamped to the sides of the beam at points on a linepassing vertically through the beam support locations, or (2)isseated on top of the beam and is itself supported at pointsdirectly over the beam
32、supports. In each case one transducer islocated on each side of the test beam at mid-span, recordingdeflection between the mounted transducers and contact pointsthat are rigid attachments located on the beam at the center ofthe span. The average of the transducer measurements are thenet deflection.6
33、.4 Data Acquisition Equipment, capable of simultaneouslyrecording data from the load and deflection transducers byeither of the following alternative methods.6.4.1 X-Y Plotter, driven by analog signals from load anddeflection transducers to record the loaddeflection curve.6.4.2 Analog Signal Samplin
34、g and Digital Conversion Us-ing Automatic Data Acquisition Equipment With a MinimumSampling Frequency of 2.5 Hz, to record load and correspond-ing deflection values from which loaddeflection curves can beproduced.6.5 Stainless Steel Plate, nominally 100 by 12 by 350 mm 4by12 by 14 in.6.6 Mechanical
35、Dial Gauge, with 0.025 mm 0.001 in.resolution.6.7 MagneticMount Dial Gauge Holder.6.8 Beam Molds, conforming to the requirements of Prac-tice C192/C192M that will produce 100 mm by 100 mm by350 mm 4 in. by 4 in. by 14 in. beams.7. Sampling, Test Beams, and Test Units7.1 Prepare a set of at least fiv
36、e beams from each sample offresh or hardened concrete.7.2 Freshly Mixed Concrete:7.2.1 Obtain samples of freshly mixed fiberreinforcedconcrete in accordance with Practice C172.7.2.2 Mold beams in accordance with Practice C31/C31Mor Practice C192/C192M and cast in one layer using a vibratingtable for
37、 consolidation. Internal vibration or rodding mayproduce nonuniform fiber distribution.FIG. 2 Load-Deflection CurvesC1399/C1399M 1037.2.3 Cure samples for a minimum of 7 days in accordancewith the standard curing procedure in Practice C31/C31M orthe procedure in Practice C192/C192M. Use the same cur
38、ingtime when comparison between or among laboratories isdesired.7.3 Hardened Concrete:7.3.1 Select samples of hardened fiber-reinforced concretefrom structures in accordance with Practice C823.7.3.2 Prepare and condition sawed beams in accordancewith Test Method C42/C42M. The sawed beams shall haved
39、imensions 100 mm by 100 mm by 350 mm 4 in. by 4 in. by14 in.8. Procedure8.1 Set the rate of platen or cross-head movement at 0.65 60.15 mm/min 0.025 6 0.005 in/min. before the beam isloaded.NOTE 4When necessary use the mechanical dial gauge to establishthe setting for the rate of platen or crosshead
40、 movement.8.2 Place the specimen on the top of the steel plate to beloaded with the specimen (see Note 5). Molded specimens orspecimens sawed from molded specimens shall be turned ontheir side from the position as cast before placing on thesupport system (see Fig. 3(a). Specimens sawed from in-place
41、FIG. 3 Schematic of Specimen Cross Sections to Indicate Permitted Flexural Tensile Surfaces During TestingC1399/C1399M 104concrete shall be loaded so that a sawed surface is the flexuraltensile surface (see Fig. 3(b). Specimens representing shot-crete shall be loaded in the same direction as the spe
42、cimen wasshot (see Fig. 3(c).NOTE 5The purpose of the stainless steel plate is to support the testbeam during the initial loading cycle to help control the expected high rateof deflection of the beam upon cracking.8.3 Place the plate and beam on the support apparatus sothat the steel plate is center
43、ed on the lower bearing blocks andthe concrete beam is centered on the steel plate. Adjust thedisplacement transducer(s) according to the chosen apparatusfor obtaining net deflection.8.4 Ensure that the XY plotter or alternate data acquisitionsystem is activated and responding to signals from all lo
44、ad anddisplacement transducers.8.5 Begin loading the beam and steel plate combination atthe set rate and continue loading until reaching a deflection of0.20 mm 0.008 in. If cracking has not occurred after reachinga deflection of 0.20 mm 0.008 in. the test is invalid. Themaximum load is not to be use
45、d to calculate modulus of rupturein accordance with Test Method C78 as this load includes loadcarried by the steel plate as well as by the concrete beam.8.6 In anticipation of reloading the cracked beam only,remove the steel plate and center the cracked beam on thelower bearing blocks retaining the
46、same orientation as duringthe initial loading test cycle. Adjust the displacement transduc-er(s) to lightly contact the beam in accordance with the chosenmethod for obtaining net deflection so that readings willimmediately be obtained upon beam reloading. Zero thedeflection recording device.8.7 Begi
47、n reloading at the specified rate used for the initialloading. Terminate the test at a deflection of 1.25 mm 0.050in. as measured from the beginning of reloading.8.8 Measure the beam and crack location as in Test MethodC78.9. Calculation9.1 Calculate the average residual strength (ARS) for eachbeam
48、to the nearest 0.01 MPa 2 psi using the loads deter-mined at reloading curve deflections of 0.50, 0.75, 1.00, and1.25 mm 0.020, 0.030, 0.040, and 0.050 in. as follows:ARS 5 PA1 PB1 PC1 PD! /4! 3 k (1)where:k = L/bd2,mm2in2ARS = average residual strength, MPa psi,PA+PB+PC+PD= sum of recorded loads at
49、 specified de-flections, N lbf,L = span length, mm in.,b = average width of beam, mm in., andd = average depth of beam, mm in.9.2 Calculate the mean ARS for each set of beams to thenearest 0.05 MPa 5 psi.10. Report10.1 The test report shall include the following information.If specific information is unknown at the time of the test thenthe word “UNKNOWN” shall be used.10.1.1 Concrete mixture proportions.10.1.2 Type and amount of fiber reinforcement.10.1.3 Test beam information including:10.1
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