ASTM C78-08
(Test Method)Standard Test Method for Flexural Strength of Concrete (Using Simple Beam with Third-Point Loading)
Standard Test Method for Flexural Strength of Concrete (Using Simple Beam with Third-Point Loading)
SIGNIFICANCE AND USE
This test method is used to determine the flexural strength of specimens prepared and cured in accordance with Test Methods C 42/C 42M or Practices C 31/C 31M or C 192/C 192M. Results are calculated and reported as the modulus of rupture. The strength determined will vary where there are differences in specimen size, preparation, moisture condition, curing, or where the beam has been molded or sawed to size.
The results of this test method may be used to determine compliance with specifications or as a basis for proportioning, mixing and placement operations. It is used in testing concrete for the construction of slabs and pavements.
SCOPE
1.1 This test method covers the determination of the flexural strength of concrete by the use of a simple beam with third-point loading.
1.2 The values stated in inch-pound units are to be regarded as the standard. The SI equivalent of inch-pound units has been rounded where necessary for practical application.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:C78–08
Standard Test Method for
Flexural Strength of Concrete (Using Simple Beam with
1
Third-Point Loading)
ThisstandardisissuedunderthefixeddesignationC 78;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscript
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* rupture. The strength determined will vary where there are
differences in specimen size, preparation, moisture condition,
1.1 Thistestmethodcoversthedeterminationoftheflexural
curing, or where the beam has been molded or sawed to size.
strength of concrete by the use of a simple beam with
3.2 The results of this test method may be used to determine
third-point loading.
compliance with specifications or as a basis for proportioning,
1.2 The values stated in inch-pound units are to be regarded
mixing and placement operations. It is used in testing concrete
asthestandard.TheSIequivalentofinch-poundunitshasbeen
for the construction of slabs and pavements.
rounded where necessary for practical application.
1.3 This standard does not purport to address all of the
4. Apparatus
safety concerns, if any, associated with its use. It is the
4.1 The testing machine shall conform to the requirements
responsibility of the user of this standard to establish appro-
of the sections on Basis of Verification, Corrections, and Time
priate safety and health practices and determine the applica-
Interval Between Verifications of PracticesE4. Hand operated
bility of regulatory limitations prior to use.
testing machines having pumps that do not provide a continu-
2. Referenced Documents ous loading in one stroke are not permitted. Motorized pumps
2 or hand operated positive displacement pumps having suffi-
2.1 ASTM Standards:
cient volume in one continuous stroke to complete a test
C 31/C 31M Practice for Making and Curing Concrete Test
without requiring replenishment are permitted and shall be
Specimens in the Field
capable of applying loads at a uniform rate without shock or
C 42/C 42M Test Method for Obtaining and Testing Drilled
interruption.
Cores and Sawed Beams of Concrete
4.2 Loading Apparatus—The third point loading method
C 192/C 192M Practice for Making and Curing Concrete
shall be used in making flexure tests of concrete employing
Test Specimens in the Laboratory
bearing blocks which will ensure that forces applied to the
C 617 Practice for Capping Cylindrical Concrete Speci-
beam will be perpendicular to the face of the specimen and
mens
applied without eccentricity. A diagram of an apparatus that
C 1077 PracticeforLaboratoriesTestingConcreteandCon-
accomplishes this purpose is shown in Fig. 1.
crete Aggregates for Use in Construction and Criteria for
4.2.1 Allapparatusformakingflexuretestsofconcreteshall
Laboratory Evaluation
be capable of maintaining the specified span length and
E4 Practices for Force Verification of Testing Machines
distances between load-applying blocks and support blocks
3. Significance and Use
constant within 60.05 in. (61.3 mm).
4.2.2 The ratio of the horizontal distance between the point
3.1 This test method is used to determine the flexural
of application of the load and the point of application of the
strength of specimens prepared and cured in accordance with
nearest reaction to the depth of the beam shall be 1.0 6 0.03.
Test Methods C 42/C 42M or Practices C 31/C 31M or C 192/
4.2.3 If an apparatus similar to that illustrated in Fig. 1 is
C 192M. Results are calculated and reported as the modulus of
used: the load-applying and support blocks should not be more
1
than2 ⁄2in.(64mm)high,measuredfromthecenterortheaxis
1
This test method is under the jurisdiction of ASTM Committee C09 on
of pivot, and should extend entirely across or beyond the full
Concrete and ConcreteAggregates and is the direct responsibility of Subcommittee
width of the specimen. Each case-hardened bearing surface in
C09.61 on Testing for Strength.
contact with the specimen shall not depart from a plane by
Current edition approved Feb. 1, 2008. Published February 2008. Originally
approved in 1930. Last previous edition approved in 2007 as C 78 – 07.
more than 0.002 in. (0.05 mm) and shall be a portion of a
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
cylinder, the axis of which is coincidental with either the axis
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
of the rod or center of the ball, whichever the block is pivoted
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. upon.The angle subtended by the curved surface of each block
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation:C78–07 Designation:C78–08
Standard Test Method for
Flexural Strength of Concrete (Using Simple Beam with
1
Third-Point Loading)
ThisstandardisissuedunderthefixeddesignationC 78;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscript
epsilon (e) 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 covers the determination of the flexural strength of concrete by the use of a simple beam with third-point
loading.
1.2 The values stated in inch-pound units are to be regarded as the standard. The SI equivalent of inch-pound units has been
rounded where necessary for practical application.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2
2.1 ASTM Standards:
C 31/C 31M Practice for Making and Curing Concrete Test Specimens in the Field
C 42/C 42M Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete
C 192/C 192M Practice for Making and Curing Concrete Test Specimens in the Laboratory
C 617 Practice for Capping Cylindrical Concrete Specimens
C 1077 PracticeforLaboratoriesTestingConcreteandConcreteAggregatesforUseinConstructionandCriteriaforLaboratory
Evaluation
E 4 Practices for Force Verification of Testing Machines
3. Significance and Use
3.1 ThistestmethodisusedtodeterminetheflexuralstrengthofspecimenspreparedandcuredinaccordancewithTestMethods
C 42/C 42M or Practices C 31/C 31M or C 192/C 192M. Results are calculated and reported as the modulus of rupture. The
strength determined will vary where there are differences in specimen size, preparation, moisture condition, curing, or where the
beam has been molded or sawed to size.
3.2 The results of this test method may be used to determine compliance with specifications or as a basis for proportioning,
mixing and placement operations. It is used in testing concrete for the construction of slabs and pavements (Note 1). pavements.
4. Apparatus
4.1 The testing machine shall conform to the requirements of the sections on Basis of Verification, Corrections, and Time
Interval Between Verifications of Practices E 4. Hand operated testing machines having pumps that do not provide a continuous
loading in one stroke are not permitted. Motorized pumps or hand operated positive displacement pumps having sufficient volume
in one continuous stroke to complete a test without requiring replenishment are permitted and shall be capable of applying loads
at a uniform rate without shock or interruption.
4.2 Loading Apparatus—The third point loading method shall be used in making flexure tests of concrete employing bearing
blocks which will ensure that forces applied to the beam will be perpendicular to the face of the specimen and applied without
eccentricity. A diagram of an apparatus that accomplishes this purpose is shown in Fig. 1.
4.2.1 All apparatus for making flexure tests of concrete shall be capable of maintaining the specified span length and distances
1
This test method is under the jurisdiction of ASTM Committee C09 on Concrete and Concrete Aggregates and is the direct responsibility of Subcommittee C09.61 on
Testing for Strength.
Current edition approved Aug. 15, 2007. Published September 2007. Originally approved in 1930. Last previous edition approved in 2002 as C78–02.
Current edition approved Feb. 1, 2008. Published February 2008. Originally approved in 1930. Last previous edition approved in 2007 as C 78 – 07.
2
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at service@astm.org. For Annual Book ofASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*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.
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C78–08
NOTE 1—This apparatus may be used inverted. If the testing machine applies force through a spherically seated head, the center pivot may be omitted,
provided one load-applying block pi
...
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