ASTM C78-94

Standard Test Method for Flexural Strength of Concrete (Using Simple Beam with Third-Point Loading)

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.

General Information

• Status: Historical
• Publication Date: 09-Jan-2002
• ICS: 91.100.30 - Concrete and concrete products
• Technical Committee: C09 - Concrete and Concrete Aggregates
• Drafting Committee: C09.61 - Testing for Strength

Relations

• Replaced By: ASTM C78-00 - Standard Test Method for Flexural Strength of Concrete (Using Simple Beam with Third-Point Loading)
• Effective Date: 10-Jan-2002
• Referred By: ASTM C688-22 - Standard Specification for Functional Additions for Use in Hydraulic Cements
• Effective Date: 10-Jan-2002
• Referred By: ASTM C1399/C1399M-10(2015) - Standard Test Method for Obtaining Average Residual-Strength of Fiber-Reinforced Concrete (Withdrawn 2024)
• Effective Date: 10-Jan-2002
• Referred By: ASTM C928/C928M-20a - Standard Specification for Packaged, Dry, Rapid-Hardening Cementitious Materials for Concrete Repairs
• Effective Date: 10-Jan-2002
• Referred By: ASTM C651-20 - Standard Test Method for Flexural Strength of Manufactured Carbon and Graphite Articles Using Four-Point Loading at Room Temperature
• Effective Date: 10-Jan-2002
• Referred By: ASTM D7972-14(2020) - Standard Test Method for Flexural Strength of Manufactured Carbon and Graphite Articles Using Three-Point Loading at Room Temperature
• Effective Date: 10-Jan-2002
• Referred By: ASTM D7958/D7958M-17 - Standard Test Method for Evaluation of Performance for FRP Composite Bonded to Concrete Substrate using Beam Test
• Effective Date: 10-Jan-2002

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: C 78 – 94
Standard Test Method for
Flexural Strength of Concrete (Using Simple Beam with
Third-Point Loading)
This standard is issued under the fixed designation C 78; the number immediately following the designation indicates the year of original
adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript
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 3.2 The results of this test method may be used to determine
compliance with specifications or as a basis for proportioning,
1.1 This test method covers the determination of the flexural
mixing and placement operations. It is used in testing concrete
strength of concrete by the use of a simple beam with
for the construction of slabs and pavements (Note 1).
third-point loading.
1.2 The values stated in inch-pound units are to be regarded
4. Apparatus
as the standard. The SI equivalent of inch-pound units has been
4.1 The testing machine shall conform to the requirements
rounded where necessary for practical application.
of the sections on Basis of Verification, Corrections, and Time
1.3 This standard does not purport to address all of the
Interval Between Verifications of Practices E 4. Hand operated
safety concerns, if any, associated with its use. It is the
testing machines having pumps that do not provide a continu-
responsibility of the user of this standard to establish appro-
ous loading in one stroke are not permitted. Motorized pumps
priate safety and health practices and determine the applica-
or hand operated positive displacement pumps having suffi-
bility of regulatory limitations prior to use.
cient volume in one continuous stroke to complete a test
2. Referenced Documents without requiring replenishment are permitted and shall be
capable of applying loads at a uniform rate without shock or
2.1 ASTM Standards:
interruption.
C 31 Practice for Making and Curing Concrete Test Speci-
2 4.2 Loading Apparatus—The third point loading method
mens in the Field
shall be used in making flexure tests of concrete employing
C 42 Test Method for Obtaining and Testing Drilled Cores
bearing blocks which will ensure that forces applied to the
and Sawed Beams of Concrete
beam will be perpendicular to the face of the specimen and
C 192 Practice for Making and Curing Concrete Test Speci-
applied without eccentricity. A diagram of an apparatus that
mens in the Laboratory
accomplishes this purpose is shown in Fig. 1.
C 617 Practice for Capping Cylindrical Concrete Speci-
4.2.1 All apparatus for making flexure tests of concrete shall
mens
be capable of maintaining the specified span length and
C 1077 Practice for Laboratories Testing Concrete and Con-
distances between load-applying blocks and support blocks
crete Aggregates for Use in Construction and Criteria for
constant within 60.05 in. (61.3 mm).
Laboratory Evaluation
4.2.2 Reactions shall be parallel to the direction of the
E 4 Practices for Force Verification of Testing Machines
applied forces at all times during the test and the ratio of
3. Significance and Use
distance between the point of load application and nearest
reaction to the depth of the beam shall not be less than one.
3.1 This test method is used to determine the flexural
4.2.3 If an apparatus similar to that illustrated in Fig. 1 is
strength of specimens prepared and cured in accordance with
used: the load-applying and support blocks should not be more
Test Methods C 42 or Practices C 31 or C 192. Results are
than 2 ⁄2 in. (64 mm) high, measured from the center or the axis
calculated and reported as the modulus of rupture. The strength
of pivot, and should extend entirely across or beyond the full
determined will vary where there are differences in specimen
width of the specimen. Each case-hardened bearing surface in
size, preparation, moisture condition, curing, or where the
contact with the specimen shall not depart from a plane by
beam has been molded or sawed to size.
more than 0.002 in. (0.05 mm) and shall be a portion of a
cylinder, the axis of which is coincidental with either the axis
This test method is under the jurisdiction of ASTM Committee C-9 on Concrete
of the rod or center of the ball, whichever the block is pivoted
and Concrete Aggregatesand is the direct responsibility of Subcommittee C09.61on
upon. The angle subtended by the curved surface of each block
Testing Concrete for Strength.
Current edition approved April 15, 1994. Published June 1994. Originally
should be at least 45° (0.79 rad). The load-applying and
published as C 78 – 30T. Last previous edition C 78 – 84.
support blocks shall be maintained in a vertical position and in
Annual Book of ASTM Standards, Vol 04.02.
3 contact with the rod or ball by means of spring-loaded screws
Annual Book of ASTM Standards, Vol 03.01.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
C78
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 pivots on a rod and the other on a ball.
NOTE 2—1 in. 5 25.4 mm.
FIG. 1 Diagrammatic View of a Suitable Apparatus for Flexure Test of Concrete by Third-Point Loading Method
that hold them in contact with the pivot rod or ball. The support blocks is greater or less than each of the gages over a
uppermost bearing plate and center point ball in Fig. 1 may be length of 1 in. (25 mm) or more. Grind, cap, or use leather
omitted when a spherically seated bearing block is used,
shims on the specimen contact surface to eliminate any gap in
provided one rod and one ball are used as pivots for the upper
excess of 0.004 in. (0.10 mm) in width. Leather shims shall be
load-applying blocks.
of uniform ⁄4 in. (6.4 mm) thickness, 1 to 2 in. (25 to 50 mm)
width, and shall extend across the full width of the specimen.
5. Testing
Gaps in excess of 0.015 in. (0.38 mm) shall be eliminated only
5.1 The test specimen shall conform to all requirements of
by capping or grinding. Grinding of lateral surfaces should be
Test Method C 42 or Practices C 31 or C 192 applicable to
minimized inasmuch as gri
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