1、Designation: C293/C293M 10Standard Test Method forFlexural Strength of Concrete (Using Simple Beam WithCenter-Point Loading)1This standard is issued under the fixed designation C293/C293M; the number immediately following the designation indicates the yearof original adoption or, in the case of revi
2、sion, 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.This standard has been approved for use by agencies of the Department of Defense.1. Scope*1.1 This test method c
3、overs determination of the flexuralstrength of concrete specimens by the use of a simple beamwith center-point loading. It is not an alternative to TestMethod C78/C78M.1.2 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach syst
4、em 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 theresp
5、onsibility 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 FieldC78/C78M Test Me
6、thod for Flexural Strength of Concrete(Using Simple Beam with Third-Point Loading)C192/C192M Practice for Making and Curing ConcreteTest Specimens in the LaboratoryC617 Practice for Capping Cylindrical Concrete SpecimensC1077 Practice for Laboratories Testing Concrete and Con-crete Aggregates for Us
7、e in Construction and Criteria forLaboratory EvaluationE4 Practices for Force Verification of Testing Machines3. Significance and Use3.1 This test method is used to determine the modulus ofrupture of specimens prepared and cured in accordance withPractices C31/C31M or C192/C192M. The strength deter-
8、mined will vary where there are differences in specimen size,preparation, moisture condition, or curing.3.2 The results of this test method may be used to determinecompliance with specifications or as a basis for proportioning,mixing and placement operations. This test method producesvalues of flexu
9、ral strength significantly higher than TestMethod C78/C78M.4. Apparatus4.1 The testing machine shall conform to the requirementsof the sections on Basis of Verification, Corrections, and TimeInterval Between Verifications of Practices E4. Hand operatedtesting machines having pumps that do not provid
10、e a continu-ous loading to failure in one stroke are not permitted. Motor-ized pumps or hand operated positive displacement pumpshaving sufficient volume in one continuous stroke to completea test without requiring replenishment are permitted and shallbe capable of applying loads at a uniform rate w
11、ithout shock orinterruption.4.2 Loading ApparatusThe mechanism by which forcesare applied to the specimen shall employ a load-applying blockand two specimen support blocks. It shall ensure that all forcesare applied perpendicular to the face of the specimen withouteccentricity. A diagram of an appar
12、atus that accomplishes thispurpose is shown in Fig. 1.4.2.1 All apparatus for making center-point loading flexuretests shall be similar to Fig. 1 and maintain the span length andcentral position of the load-applying block with respect to thesupport blocks constant within 61.0 mm 60.05 in.4.2.2 React
13、ions shall be parallel to the direction of theapplied load at all times during the test, and the ratio of thehorizontal distance between the point of load application andnearest reaction to the depth of the beam shall be 1.5 6 2%.4.2.3 The load-applying and support blocks shall not bemore than 65 mm
14、 2.50 in. high, measured from the center orthe axis of pivot, and shall extend at least across the full width1This test method is under the jurisdiction of ASTM Committee C09 onConcrete and Concrete Aggregates and is the direct responsibility of SubcommitteeC09.61 on Testing for Strength.Current edi
15、tion approved Aug. 1, 2010. Published September 2010. Originallyapproved in 1952. Last previous edition approved in 2008 as C29308. DOI:10.1520/C0293_C0293M-10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of
16、 ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary 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.of the specimen. Eac
17、h hardened bearing surface in contact withthe specimen shall not depart from a plane by more than 0.05mm 0.002 in. and shall be a portion of a cylinder, the axis ofwhich is coincidental with either the axis of the rod or centerof the ball, whichever the block is pivoted upon. The anglesubtended by t
18、he curved surface of each block shall be at least0.80 rad 45. The load-applying and support blocks shall bemaintained in a vertical position and in contact with the rod orball by means of spring-loaded screws that hold them incontact with the pivot rod or ball. The rod in the centerload-applying blo
19、ck in Fig. 1 may be omitted when a spheri-cally seated bearing block is used.5. Testing5.1 The test specimen shall conform to all requirements ofPractice C31/C31M or C192/C192M applicable to beam speci-mens and shall have a test span within 2 % of being three timesits depth as tested. The sides of t
20、he specimen shall be at rightangles with the top and bottom. All surfaces shall be smoothand free of scars, indentations, holes, or inscribed identificationmarks.5.2 The individual who tests concrete beams for acceptancetesting shall meet the concrete laboratory requirements ofPractice C1077 includi
21、ng Test Method C293/C293M as arelevant test.NOTE 1The testing laboratory performing this test method may beevaluated in accordance with Practice C1077.6. Procedure6.1 Flexural tests of moist-cured specimens shall be made assoon as practical after removal from moist storage. Surfacedrying of the spec
22、imen results in a reduction in the measuredmodulus of rupture.6.2 Turn the test specimen on its side with respect to itsposition as molded and center it on the support blocks. Centerthe loading system in relation to the applied force. Bring theload-applying block in contact with the surface of the s
23、pecimenat the center and apply a load of between 3 and 6 % of theestimated ultimate load. Using 0.10 mm 0.004 in. and 0.40mm 0.015 in. leaf-type feeler gages, determine whether anygap between the specimen and the load-applying or supportblocks is greater or less than each of the gages over a length
24、of25 mm 1 in. or more. Grind, cap, or use leather shims on thespecimen contact surface to eliminate any gap in excess of 0.10mm 0.004 in. Leather shims shall be of uniform 6 mm 0.25in. thickness, 25 to 50 mm 1.0 to 2.0 in. in width, and shallextend across the full width of the specimen. Gaps in exce
25、ss of0.40 mm 0.015 in. shall be eliminated only by capping orgrinding. Grinding of lateral surfaces shall be minimizedinasmuch as grinding may change the physical characteristicsof the specimens. Capping shall be in accordance with appli-cable sections of Practice C617.6.3 Load the specimen continuo
26、usly and without shock. Theload shall be applied at a constant rate to the breaking point.Apply the load so that the maximum stress on the tension faceincreases at a rate between 0.9 and 1.2 MPa/min 125 and 175psi/min. The loading rate is computed using the followingequation:r 52Sbd23L(1)where:r = l
27、oading rate, N/min lb/min,S = rate of increase in the maximum stress on the tensionface, MPa/min psi/min,b = average width of the specimen as oriented for testing,mm in.,d = average depth of the specimen as oriented for testing,mm in., andL = span length, mm in.NOTE 1Apparatus may be used inverted.F
28、IG. 1 Schematic of a Suitable Apparatus for Flexure Test of Concrete by Center-Point Loading Method.C293/C293M 1027. Measurement of Specimens After Test7.1 To determine the dimensions of the specimen sectionfor use in calculating modulus of rupture, take measurementsacross one of the fractured faces
29、 after testing. The width anddepth are measured with the specimen as oriented for testing.For each dimension, take one measurement at each edge andone at the center of the cross section. Use the three measure-ments for each direction to determine the average width and theaverage depth. Take all meas
30、urements to the nearest 1 mm0.05 in. If the fracture occurs at a capped section, include thecap thickness in the measurement.8. Calculation8.1 Calculate the modulus of rupture as follows:R 53 PL2bd2(2)where:R = modulus of rupture, MPa psi,P = maximum applied load indicated by the testing ma-chine, N
31、 lbf,L = span length, mm in.,b = average width of specimen, at the fracture, mm in.,andd = average depth of specimen, at the fracture, mm in.NOTE 2The weight of the beam is not included in the abovecalculation.9. Report9.1 Report the following information:9.1.1 Identification number,9.1.2 Average wi
32、dth to the nearest 1 mm 0.05 in., at thefracture,9.1.3 Average depth to the nearest 1 mm 0.05 in., at thefracture,9.1.4 Span length in mm in.,9.1.5 Maximum applied load in N lbf,9.1.6 Modulus of rupture calculated to the nearest 0.05 MPa5 psi,9.1.7 Record of curing and apparent moisture condition of
33、the specimens at the time of test,9.1.8 If specimens were capped, ground, or if leather shimswere used,9.1.9 Defects in specimens, and9.1.10 Age of specimens.10. Precision and Bias10.1 PrecisionThe coefficient of variation of test resultshas been observed to be dependent on the strength level of the
34、beams.3The single operator coefficient of variation has beenfound to be 4.4 %. Therefore, results of two properly con-ducted tests by the same operator on beams made from thesame batch sample are not expected to differ from each otherby more than 12 %. The multilaboratory coefficient of variationhas
35、 been found to be 5.3 %. Therefore, results of two differentlaboratories on beams made from the same batch sample arenot expected to differ from each other by more than 15 %.10.2 BiasBecause there is no accepted standard for deter-mining bias in this test method, no statement on bias is made.11. Key
36、words11.1 beams; concrete; flexural strength testing; modulus ofruptureSUMMARY OF CHANGESCommittee C09 has identified the location of selected changes to this test method since the last issue,C29308, that may impact the use of this test method. (Approved August 1, 2010)(1) Revised the standard as a
37、dual unit test method.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringeme
38、nt of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or
39、for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views kno
40、wn to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting AST
41、M at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).3See “Improved Concrete Quality Control Proced
42、ures Using Third PointLoading” by P. M. Carrasquillo and R. L. Carrasquillo, Research Report 119-1F,Project 3-9-87-1119, Center For Transportation Research, The University of Texasat Austin, November 1987, for information as to the relationship of strength andvariability under center point loading.C293/C293M 103
