ASTM C31/C31M-00
(Practice)Standard Practice for Making and Curing Concrete Test Specimens in the Field
Standard Practice for Making and Curing Concrete Test Specimens in the Field
SCOPE
1.1 This practice covers procedures for making and curing cylindrical and prismatic beam specimens from representative samples of fresh concrete for a construction project.
1.2 The concrete used to make the molded specimens shall be sampled after all on-site adjustments have been made to the mixture proportions, including the addition of mix water and admixtures. This practice is not satisfactory for making specimens from concrete not having a measurable slump or requiring other sizes and shapes of specimens.
1.3 The values stated in either inch-pound units or SI units shall be regarded separately as standard. The SI units are shown in brackets. The values stated may not be exact equivalents; therefore each system must be used independently of the other. Combining values from the two units may result in nonconformance.
1.4 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.
1.5 The text of this standard references notes which provide explanatory material. These notes shall not be considered as requirements of the standard.
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Designation: C 31/C 31M – 00
Standard Practice for
Making and Curing Concrete Test Specimens in the Field
This standard is issued under the fixed designation C 31/C 31M; 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 Concrete by the Pressure Method
C 330 Specification for Lightweight Aggregate for Concrete
1.1 This practice covers procedures for making and curing
Masonry Units
cylinder and beam specimens from representative samples of
C 403/C 403M Test Method for Time of Setting of Con-
fresh concrete for a construction project.
crete Mixtures by Penetration Resistance
1.2 The concrete used to make the molded specimens shall
C 470/C 470M Specification for Molds for Forming Con-
be sampled after all on-site adjustments have been made to the
crete Test Cylinders Vertically
mixture proportions, including the addition of mix water and
C 511 Specification for Moist Cabinets, Moist Rooms, and
admixtures. This practice is not satisfactory for making speci-
Water Storage Tanks Used in the Testing of Hydraulic
mens from concrete not having measurable slump or requiring
Cements and Concretes
other sizes or shapes of specimens.
C 617 Practice for Capping Cylindrical Concrete Speci-
1.3 The values stated in either inch-pound units or SI units
mens
shall be regarded separately as standard. The SI units are
C 1064 Test Method for Temperature of Freshly Mixed
shown in brackets. The values stated may not be exact
Portland-Cement Concrete
equivalents; therefore each system must be used independently
2.2 American Concrete Institute Publication:
of the other. Combining values from the two units may result
CP-1 Concrete Field Testing Technician, Grade I
in nonconformance.
309R Guide for Consolidation of Concrete
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3. Significance and Use
responsibility of the user of this standard to establish appro-
3.1 This practice provides standardized requirements for
priate safety and health practices and determine the applica-
making, curing, protecting, and transporting concrete test
bility of regulatory limitations prior to use.
specimens under field conditions.
1.5 The text of this standard references notes which provide
3.2 If the specimens are made and standard cured, as
explanatory material. These notes shall not be considered as
stipulated herein, the resulting strength test data when the
requirements of the standard.
specimens are tested are able to be used for the following
2. Referenced Documents purposes:
3.2.1 Acceptance testing for specified strength,
2.1 ASTM Standards:
3.2.2 Checking adequacy of mixture proportions for
C 138 Test Method for Unit Weight, Yield, and Air Content
strength, and
(Gravimetric) of Concrete
3.2.3 Quality control.
C 143/C 143M Test Method for Slump of Hydraulic Ce-
3.3 If the specimens are made and field cured, as stipulated
ment Concrete
2 herein, the resulting strength test data when the specimens are
C 172 Practice for Sampling Freshly Mixed Concrete
tested are able to be used for the following purposes:
C 173 Test Method for Air Content of Freshly Mixed
2 3.3.1 Determination of whether a structure is capable of
Concrete by the Volumetric Method
being put in service,
C 192/C 192M Practice for Making and Curing Concrete
2 3.3.2 Comparison with test results of standard cured speci-
Test Specimens in the Laboratory
mens or with test results from various in-place test methods,
C 231 Test Method for Air Content of Freshly Mixed
3.3.3 Adequacy of curing and protection of concrete in the
structure, or
This practice is under the jurisdiction of ASTM Committee C09 on Concrete
and Concrete Aggregatesand is the direct responsibility of Subcommittee C09.61 on
Testing Concrete for Strength.
Current edition approved Aug. 10, 2000. Published October 2000. Originally Annual Book of ASTM Standards, Vol 04.01.
published as C 31 – 20. Last previous edition C 31/C 31M – 98. Available from American Concrete Institute, P.O. Box 9094, Farmington Hills,
Annual Book of ASTM Standards, Vol 04.02. MI 48333-9094.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
C 31/C 31M
3.3.4 Form or shoring removal time requirements. 4.8 Slump Apparatus— The apparatus for measurement of
slump shall conform to the requirements of Test Method
4. Apparatus
C 143/C 143M.
4.1 Molds, General— Molds for specimens or fastenings
4.9 Sampling Receptacle—The receptacle shall be a suitable
thereto in contact with the concrete shall be made of steel, cast
heavy gage metal pan, wheelbarrow, or flat, clean nonabsor-
iron, or other nonabsorbent material, nonreactive with concrete
bent board of sufficient capacity to allow easy remixing of the
containing portland or other hydraulic cements. Molds shall
entire sample with a shovel or trowel.
hold their dimensions and shape under all conditions of use.
4.10 Air Content Apparatus—The apparatus for measuring
Molds shall be watertight during use as judged by their ability
air content shall conform to the requirements of Test Methods
to hold water poured into them. Provisions for tests of water
C 173 or C 231.
leakage are given in the Test Methods for Elongation, Absorp-
4.11 Temperature Measuring Devices—The temperature
tion, and Water Leakage section of Specification C 470/
measuring devices shall conform to the applicable require-
C 470M. A suitable sealant, such as heavy grease, modeling
ments of Test Method C 1064.
clay, or microcrystalline wax shall be used where necessary to
prevent leakage through the joints. Positive means shall be
5. Testing Requirements
provided to hold base plates firmly to the molds. Reusable
5.1 Cylindrical Specimens—Compressive or splitting ten-
molds shall be lightly coated with mineral oil or a suitable
sile strength specimens shall be cylinders cast and allow to set
nonreactive form release material before use.
in an upright position, with a length equal to twice the
4.2 Cylinder Molds— Molds for casting concrete test speci-
diameter. The standard specimen shall be the 6 by 12-in. [150
mens shall conform to the requirements of Specification
by 300-mm] cylinder when the nominal maximum size of the
C 470/C 470M.
coarse aggregate does not exceed 2 in. [50 mm] (Note 2, Note
4.3 Beam Molds—Beam molds shall be of the shape and
3). When the nominal maximum size of the coarse aggregate
dimensions required to produce the specimens stipulated in 5.2.
does exceed 2 in. [50 mm], either the concrete sample shall be
The inside surfaces of the molds shall be smooth. The sides,
treated by wet sieving as described in Practice C 172 or the
bottom, and ends shall be at right angles to each other and shall
diameter of the cylinder shall be at least three times the
be straight and true and free of warpage. Maximum variation
nominal maximum size of coarse aggregate in the concrete. For
from the nominal cross section shall not exceed ⁄8 in. [3 mm]
acceptance testing for specified strength, cylinders smaller than
for molds with depth or breadth of 6 in. [150 mm] or more.
6 by 12 in. [150 by 300 mm] shall not be used, unless another
Molds shall produce specimens at least as long but not more
size is specified (Note 4).
than ⁄16 in. [2 mm] shorter than the required length in 5.2.
NOTE 2—The nominal maximum size is the smallest sieve opening
4.4 Tamping Rod— A round, straight steel rod with the
through which the entire amount of aggregate is permitted to pass.
dimensions conforming to those in Table 1, having the tamping
NOTE 3—When molds in SI units are required and not available,
end or both ends rounded to a hemispherical tip of the same
equivalent inch-pound unit size mold should be permitted.
diameter as the rod.
NOTE 4—For uses other than acceptance testing for specified strength,
4.5 Vibrators—Internal vibrators shall be used. The vibrator
a 4 by 8 in. [100 by 200 mm] or 5 by 10 in. [125 by 250 mm] cylinder may
frequency shall be at least 7000 vibrations per minute [150 Hz]
be suitable. However, the diameter of any cylinder shall be at least three
while the vibrator is operating in the concrete. The diameter of
times the nominal maximum size of the coarse aggregate in the concrete
a round vibrator shall be no more than one-fourth the diameter (Note 2). When cylinders smaller than the standard size are used,
within-test variability has been shown to be higher but not to a statistically
of the cylinder mold or one-fourth the width of the beam mold.
significant degree. The compressive strength results are affected by a
Other shaped vibrators shall have a perimeter equivalent to the
number of factors including cylinder size.
circumference of an appropriate round vibrator. The combined
length of the vibrator shaft and vibrating element shall exceed 5.2 Beam Specimens— Flexural strength specimens shall be
the depth of the section being vibrated by at least 3 in. [75
beams of concrete cast and hardened in the horizontal position.
mm]. The vibrator frequency shall be checked periodically. The length shall be at least 2 in. [50 mm] greater than three
times the depth as tested. The ratio of width to depth as molded
NOTE 1—For information on size and frequency of various vibrators
shall not exceed 1.5. The standard beam shall be 6 by 6 in. [150
and a method to periodically check vibrator frequency see ACI 309.
by 150 mm] in cross section, and shall be used for concrete
4.6 Mallet—A mallet with a rubber or rawhide head weigh-
with nominal maximum size coarse aggregate up to 2 in. [50
ing 1.25 6 0.50 lb [0.6 6 0.2 kg] shall be used.
mm] (Note 2). When the nominal maximum size of the coarse
4.7 Small Tools— Shovels, hand-held floats, scoops, and a
aggregate exceeds 2 in. [50 mm], the smaller cross sectional
vibrating-reed tachometer shall be provided.
dimension of the beam shall be at least three times the nominal
maximum size of the coarse aggregate. Unless required by
TABLE 1 Tamping Rod Requirements
project specifications, beams made in the field shall not have a
A
Rod Dimensions
Diameter of Cylinder or Width of
width or depth of less than 6 in. [150 mm].
Diameter Length of Rod
Beam in. [mm]
5.3 Field Technicians—The field technicians making and
in. [mm] in. [mm]
curing specimens for acceptance testing shall be certified ACI
<6 [150] 3/8 [10] 12 [300]
Field Testing Technicians, Grade I or equivalent. Equivalent
6 [150] 5/8 [16] 20 [500]
9 [225] 5/8 [16] 26 [650]
personnel certification programs shall include both written and
A 1
Rod tolerances length 64 in. [100 mm] and diameter 6 ⁄16 in. [2 mm]. performance examinations, as outlined in ACI CP-1.
C 31/C 31M
TABLE 3 Molding Requirements by Rodding
6. Sampling Concrete
Number of Layers of
6.1 The samples used to fabricate test specimens under this
Specimen Type Number of Roddings
Approximately Equal
and Size per Layer
standard shall be obtained in accordance with Practice C 172
Depth
unless an alternative procedure has been approved.
Cylinders:
6.2 Record the identification of the sample with respect to
Diameter, in. [mm]
4 [100] 2 25
the location of the concrete represented and the time of casting.
6 [150] 3 25
9 [225] 4 50
7. Slump, Air Content, and Temperature
Beams:
7.1 Slump—Measure and record the slump of each batch of
Width, in. [mm]
concrete from which specimens are made immediately after
6 [150] to 8 [200] 2 see 8.3
remixing in the receptacle, as required in Test Method C 143/
>8 [200] 3 or more equal depths, see 8.3
each not to exceed
C 143M.
6 in. [150 mm].
7.2 Air Content— Determine and record the air content in
accordance with either Test Method C 173 or Test Method
C 231. The concrete used in performing the air content test
TABLE 4 Molding Requirements by Vibration
shall not be used in fabricating test specimens.
Number of
7.3 Temperature— Determine and record the temperature in
Specimen Type Number of Vibrator Approximate Depth of
accordance with Test Method C 1064. and Size Layers Insertions Layer, in. [mm]
per Layer
NOTE 5—Some specifications may require the measurement of the unit
Cylinders:
weight of concrete. The volume of concrete produced per batch may be
Diameter, in. [mm]
desired on some projects. Also, additional information on the air content
4 [100] 2 1 one-half depth of specimen
measurements may be desired. Test Method C 138 is used to measure the
6 [150] 2 2 one-half depth of specimen
unit weight, yield, and gravimetric air content of freshly mixed concrete. 9 [225] 2 4 one-half depth of specimen
Beams:
8. Molding Specimens
Width, in. [mm]
8.1 Place of Molding— Mold specimens promptly on a 6 [150] to 8 [200] 1 see 8.4.2 depth of specimen
over 8 [200] 2 or more see 8.4.2 8 [200] as near as
level, rigid surface, free of vibration and other disturbances, at
practicable
a place as near as practicable to the location where they are to
be stored.
8.2 Casting Cylinders—Select the proper tamping rod from
Select a small tool, of the size and shape large enough so each
4.4 and Table 1 or the proper vibrator from 4.5. Determine the
amount of concrete obtained from the sampling receptacle is
method of consolidation from Table 2, unless another method
representative and small enough so concrete is not lost when
is specified. If the method of consolidation is rodding, deter-
placed in the mold. Each layer shall be consolidated as
mine molding requirements from Table 3. If the method of
required. In placing the final layer, add an amount of concrete
consolidation is vibration, determine molding requirements
that will fill the mold after consolidation. Place the concrete so
from Table 4. Select a small tool of a size and shape large
that it is uniformly distributed within each layer with a
enough so each amount of concrete obtained from the sampling
minimum of segregation.
receptacle will be representative and small enough so concrete
8.4 Consolidation— The methods of consolidation for this
is not lost when being placed in the mold. While placing the
practice are rodding or internal vibration.
concrete in the mold, move the small tool around the perimeter
8.4.1 Rodding—Place the concrete in the mold, in the
of the mold opening to ensure an even distribution of the
required number of layers of approximately equal volume. Rod
concrete and minimize segregation. Each layer of concrete
each layer with the rounded end of the rod using the required
shall be consolidated as
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