ASTM C31/C31M-24a

Standard Practice for Making and Curing Concrete Test Specimens in the Field

SIGNIFICANCE AND USE
4.1 This practice provides standardized requirements for making, and curing test specimens in the field. This practice also provides requirements for transporting test specimens to the laboratory, and for curing test specimens in the laboratory. Depending on their purpose, test specimens are either standard-cured, or field-cured.  
4.2 Uses of the test results of standard-cured test specimens include the following purposes:  
4.2.1 Acceptance testing for specified concrete strength,  
Note 2: Specification C94/C94M requires compressive-strength test specimens for acceptance to be standard-cured.  
4.2.2 Checking adequacy of mixture proportions for concrete strength, and  
4.2.3 Quality control.  
4.3 Uses of test results of field-cured test specimens include:  
4.3.1 Estimation of the in place concrete strength,  
4.3.2 Comparison with test results of standard cured specimens or with test results from various in-place test methods,  
4.3.3 Adequacy of curing and protection of concrete in the structure,  
4.3.4 Form or shoring removal time requirements, or  
4.3.5 Post-tensioning.
SCOPE
1.1 This practice covers procedures for making and curing cylinder and beam specimens from representative samples of fresh concrete for a construction project.  
1.2 This practice is not intended for making specimens from concrete not having measurable slump or requiring other sizes or shapes of specimens.  
1.3 This practice is not applicable to lightweight insulating concrete or controlled low strength material (CLSM).
Note 1: Test Method C495/C495M covers the preparation of specimens and the determination of the compressive strength of lightweight insulating concrete. Test Method D4832 covers procedures for the preparation, curing, transporting and testing of cylindrical test specimens of CLSM.  
1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.  
1.5 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. (Warning—Fresh hydraulic cementitious mixtures are caustic and may cause chemical burns to exposed skin and tissue upon prolonged exposure.2)  
1.6 The text of this standard references notes which provide explanatory material. These notes shall not be considered as requirements of the standard.  
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Mar-2024
• ICS: 91.100.30 - Concrete and concrete products
• Technical Committee: C09 - Concrete and Concrete Aggregates
• Drafting Committee: C09.61 - Testing for Strength

Relations

• Replaces: ASTM C31/C31M-24 - Standard Practice for Making and Curing Concrete Test Specimens in the Field
• Effective Date: 01-Apr-2024
• Refers: ASTM C94/C94M-24 - Standard Specification for Ready-Mixed Concrete
• Effective Date: 01-Jan-2024
• Refers: ASTM C1064/C1064M-23 - Standard Test Method for Temperature of Freshly Mixed Hydraulic-Cement Concrete
• Effective Date: 01-Dec-2023
• Refers: ASTM C231/C231M-22 - Standard Test Method for Air Content of Freshly Mixed Concrete by the Pressure Method
• Effective Date: 01-Jun-2022
• Refers: ASTM C1064/C1064M-17 - Standard Test Method for Temperature of Freshly Mixed Hydraulic-Cement Concrete
• Effective Date: 01-Oct-2017
• Refers: ASTM C173/C173M-16 - Standard Test Method for Air Content of Freshly Mixed Concrete by the Volumetric Method
• Effective Date: 01-Feb-2016
• Referred By: ASTM C1037-16 - Standard Practice for Inspection of Underground Precast Concrete Utility Structures
• Effective Date: 01-Apr-2024
• Referred By: ASTM D7853-13(2020) - Standard Test Method for Hydraulic Pullout Resistance of a Geomembrane with Locking Extensions Embedded in Concrete
• Effective Date: 01-Apr-2024
• Referred By: ASTM C1433M-22 - Standard Specification for Precast Reinforced Concrete Monolithic Box Sections for Culverts, Storm Drains, and Sewers (Metric)
• Effective Date: 01-Apr-2024
• Referred By: ASTM C858-19 - Standard Specification for Underground Precast Concrete Utility Structures
• Effective Date: 01-Apr-2024
• Referred By: ASTM C173/C173M-24 - Standard Test Method for Air Content of Freshly Mixed Concrete by the Volumetric Method
• Effective Date: 01-Apr-2024
• Referred By: ASTM C1504M-20 - Standard Specification for Manufacture of Precast Reinforced Concrete Three-Sided Structures for Culverts and Storm Drains (Metric)
• Effective Date: 01-Apr-2024
• Referred By: ASTM C361M-22 - Standard Specification for Reinforced Concrete Low-Head Pressure Pipe (Metric)
• Effective Date: 01-Apr-2024
• Referred By: ASTM C361-22 - Standard Specification for Reinforced Concrete Low-Head Pressure Pipe
• Effective Date: 01-Apr-2024
• Referred By: ASTM D4506-21 - Standard Test Method for Determining In Situ Modulus of Deformation of a Rock Mass Using the Radial Jacking Test
• Effective Date: 01-Apr-2024

Overview

ASTM C31/C31M-24a - Standard Practice for Making and Curing Concrete Test Specimens in the Field is a widely adopted standard published by ASTM International. This practice outlines precise procedures for making and curing concrete cylinder and beam specimens derived from freshly mixed concrete, enabling consistent field testing for construction projects. It includes requirements for standard curing, field curing, laboratory transport, and subsequent laboratory curing, ensuring reliable evaluation of concrete properties.

Adherence to ASTM C31/C31M is critical for validating concrete performance, fulfilling quality control, and meeting contractual and regulatory obligations. The implementation of this standard supports accurate assessment of concrete strength, uniformity, and durability, critical factors in safe and robust construction.

Key Topics

• Types of Test Specimens:

  • Standard-cured specimens: Prepared and maintained under controlled conditions for acceptance testing, checking mixture proportions, and quality control.
  • Field-cured specimens: Cured in the same environment as in-place concrete to estimate actual structural performance.

• Field and Laboratory Procedures:

  • Detailed steps for mixing, molding, consolidating, and finishing both cylinder and beam specimens.
  • Requirements for field storage, initial curing, and transportation to laboratories for final curing and testing.
  • Use of standardized molds, tamping rods, vibrators, and other apparatus as defined by related ASTM specifications.

• Environmental Controls:

  • Strict temperature and moisture requirements for initial and final curing to assure the accuracy of concrete strength measurements.
  • Measures for moisture retention and protection against environmental exposure or damage during transportation.

• Reporting and Documentation:

  • Guidelines for tracking, labeling, and reporting specimen identity, curing methods, sampling location, and fresh concrete test results for traceability and compliance.

Applications

• Acceptance Testing: Ensures delivered concrete meets specified strength requirements before incorporation into permanent structures.
• Mixture Evaluation: Supports verification and adjustment of concrete mixture proportions based on measured performance.
• Quality Control: Provides a basis for ongoing evaluation of concrete quality, enabling early identification of potential material or process issues.
• In-Place Strength Estimation: Field-cured specimens allow for realistic assessment of in-place concrete performance compared to controlled laboratory samples.
• Construction Timing Decisions: Field-cured data helps determine appropriate timing for form removal, shoring decisions, and post-tensioning operations.

Compliance with ASTM C31/C31M is mandated for most public infrastructure and commercial building projects, ensuring construction integrity, safety, and regulatory adherence.

Related Standards

ASTM C31/C31M references and complements several key ASTM and industry standards, including:

• ASTM C94/C94M - Specification for Ready-Mixed Concrete
• ASTM C125 - Terminology Relating to Concrete and Concrete Aggregates
• ASTM C138/C138M - Density, Yield, and Air Content of Concrete
• ASTM C143/C143M - Slump of Hydraulic-Cement Concrete
• ASTM C172/C172M - Sampling Freshly Mixed Concrete
• ASTM C470/C470M - Molds for Forming Concrete Test Cylinders
• ASTM C617/C617M - Capping Cylindrical Concrete Specimens
• ASTM C511 - Moist Rooms, Cabinets, and Storage Tanks for Curing

In addition, methods for lightweight insulating concrete (ASTM C495/C495M) and controlled low strength material (ASTM D4832) provide specialized procedures where ASTM C31/C31M does not apply.

---

Keywords: ASTM C31/C31M, concrete test specimens, standard curing, field curing, strength testing, concrete quality control, laboratory procedures, concrete standards.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: C31/C31M − 24a
Standard Practice for
Making and Curing Concrete Test Specimens in the Field
This standard is issued under the fixed designation C31/C31M; 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 (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
1.1 This practice covers procedures for making and curing
mendations issued by the World Trade Organization Technical
cylinder and beam specimens from representative samples of
Barriers to Trade (TBT) Committee.
fresh concrete for a construction project.
1.2 This practice is not intended for making specimens from
2. Referenced Documents
concrete not having measurable slump or requiring other sizes
2.1 ASTM Standards:
or shapes of specimens.
C94/C94M Specification for Ready-Mixed Concrete
1.3 This practice is not applicable to lightweight insulating
C125 Terminology Relating to Concrete and Concrete Ag-
concrete or controlled low strength material (CLSM).
gregates
C138/C138M Test Method for Density (Unit Weight), Yield,
NOTE 1—Test Method C495/C495M covers the preparation of speci-
and Air Content (Gravimetric) of Concrete
mens and the determination of the compressive strength of lightweight
insulating concrete. Test Method D4832 covers procedures for the C143/C143M Test Method for Slump of Hydraulic-Cement
preparation, curing, transporting and testing of cylindrical test specimens
Concrete
of CLSM.
C172/C172M Practice for Sampling Freshly Mixed Con-
1.4 The values stated in either SI units or inch-pound units crete
are to be regarded separately as standard. The values stated in
C173/C173M Test Method for Air Content of Freshly Mixed
each system may not be exact equivalents; therefore, each Concrete by the Volumetric Method
system shall be used independently of the other. Combining
C231/C231M Test Method for Air Content of Freshly Mixed
values from the two systems may result in non-conformance Concrete by the Pressure Method
with the standard.
C330/C330M Specification for Lightweight Aggregates for
Structural Concrete
1.5 This standard does not purport to address all of the
C403/C403M Test Method for Time of Setting of Concrete
safety concerns, if any, associated with its use. It is the
Mixtures by Penetration Resistance
responsibility of the user of this standard to establish appro-
C470/C470M Specification for Molds for Forming Concrete
priate safety, health, and environmental practices and deter-
Test Cylinders Vertically
mine the applicability of regulatory limitations prior to use.
C495/C495M Test Method for Compressive Strength of
(Warning—Fresh hydraulic cementitious mixtures are caustic
Lightweight Insulating Concrete
and may cause chemical burns to exposed skin and tissue upon
C511 Specification for Mixing Rooms, Moist Cabinets,
prolonged exposure. )
Moist Rooms, and Water Storage Tanks Used in the
1.6 The text of this standard references notes which provide
Testing of Hydraulic Cements and Concretes
explanatory material. These notes shall not be considered as
C617/C617M Practice for Capping Cylindrical Concrete
requirements of the standard.
Specimens
1.7 This international standard was developed in accor-
C1064/C1064M Test Method for Temperature of Freshly
dance with internationally recognized principles on standard-
Mixed Hydraulic-Cement Concrete
C1077 Practice for Agencies Testing Concrete and Concrete
Aggregates for Use in Construction and Criteria for
This practice is under the jurisdiction of ASTM Committee C09 on Concrete
Testing Agency Evaluation
and Concrete Aggregates and is the direct responsibility of Subcommittee C09.61
on Testing for Strength.
Current edition approved April 1, 2024. Published April 2024. Originally
approved in 1920. Last previous edition approved in 2024 as C31/C31M–24. DOI: For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10.1520/C0031_C0031M-24A. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
See Section on Safety Precautions, Manual of Aggregate and Concrete Testing, Standards volume information, refer to the standard’s Document Summary page on
Annual Book of ASTM Standards, Vol. 04.02. 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
C31/C31M − 24a
C1611/C1611M Test Method for Slump Flow of Self- 4.2 Uses of the test results of standard-cured test specimens
Consolidating Concrete include the following purposes:
C1758/C1758M Practice for Fabricating Test Specimens 4.2.1 Acceptance testing for specified concrete strength,
with Self-Consolidating Concrete
NOTE 2—Specification C94/C94M requires compressive-strength test
D4832 Test Method for Preparation and Testing of Con-
specimens for acceptance to be standard-cured.
trolled Low Strength Material (CLSM) Cylindrical Test
4.2.2 Checking adequacy of mixture proportions for con-
Specimens
crete strength, and
2.2 American Concrete Institute Publication:
4.2.3 Quality control.
309R Guide for Consolidation of Concrete
4.3 Uses of test results of field-cured test specimens include:
3. Terminology
4.3.1 Estimation of the in place concrete strength,
4.3.2 Comparison with test results of standard cured speci-
3.1 Definitions:
mens or with test results from various in-place test methods,
3.1.1 For definitions of terms used in this practice, refer to
4.3.3 Adequacy of curing and protection of concrete in the
Terminology C125.
structure,
3.2 Definitions of Terms Specific to This Standard:
4.3.4 Form or shoring removal time requirements, or
3.2.1 acceptance test specimens, n—standard-cured test
4.3.5 Post-tensioning.
specimens intended for evaluating whether the supplied con-
crete complies with the specification.
5. Apparatus
3.2.2 field-curing, n—storing test specimens in the field
5.1 Molds, General—Molds for specimens or fastenings
under an environmental temperature and moisture environment
thereto in contact with the concrete shall be made of steel, cast
similar to the in-place concrete.
iron, or other nonabsorbent material, nonreactive with concrete
3.2.3 initial-curing, n—the storage of test specimens in the containing portland or other hydraulic cements. Molds shall
field after molding and before transporting the specimens to the hold their dimensions and shape under all conditions of use.
laboratory. Molds shall be watertight during use as judged by their ability
3.2.3.1 Discussion—Initial curing covers the time period to hold water poured into them. Provisions for tests of water
from molding to transporting the test specimens.
leakage are given in the Test Methods for Elongation,
Absorption, and Water Leakage section of Specification C470/
3.2.4 initial standard curing temperature, n—temperature of
C470M. A suitable sealant, such as heavy grease, modeling
the environment surrounding the specimen during initial stan-
clay, or microcrystalline wax shall be used where necessary to
dard curing.
prevent leakage through the joints. Positive means shall be
3.2.4.1 Discussion—The environment surrounding
provided to hold base plates firmly to the molds. Reusable
standard-cured test specimens may be air, water, or damp sand.
molds shall be lightly coated with mineral oil or a suitable
The temperature of the environment surrounding standard-
nonreactive form release material before use.
cured test specimen might not be the same as the concrete
temperature.
5.2 Cylinder Molds—Molds for casting concrete test speci-
mens shall conform to the requirements of Specification
3.2.5 standard-curing, n—storing test specimens in an en-
C470/C470M. Cardboard cylinder molds shall not be used for
vironment of a specified temperature range, and under condi-
standard-cured specimens.
tions that control the loss of moisture from the test specimens
while the test specimens are in the field and while in the
5.3 Beam Molds—Beam molds shall be of the shape and
laboratory.
dimensions required to produce the specimens stipulated in 6.2.
3.2.5.1 Discussion—Standard-curing is intended to reduce
The inside surfaces of the molds shall be smooth. The sides,
the influence of variations by standardizing the temperature
bottom, and ends shall be at right angles to each other and shall
and moisture environment on the strength development of test
be straight and true and free of warpage. Maximum variation
specimens. Standard-curing includes requirements for the cur-
from the nominal cross section shall not exceed 3 mm [ ⁄8 in.]
ing environment while the test specimens are in the field
for molds with depth or breadth of 150 mm [6 in.] or more.
(10.1.2) and while the test specimens are in the laboratory
Molds shall produce specimens at least as long but not more
(10.1.3). 1
than 2 mm [ ⁄16 in.] shorter than the required length in 6.2.
5.4 Tamping Rod—A round, smooth, straight, steel rod with
4. Significance and Use
a diameter conforming to the requirements in Table 1. The
4.1 This practice provides standardized requirements for
length of the tamping rod shall be at least 100 mm [4 in.]
making, and curing test specimens in the field. This practice
also provides requirements for transporting test specimens to
the laboratory, and for curing test specimens in the laboratory.
TABLE 1 Tamping Rod Diameter Requirements
Depending on their purpose, test specimens are either standard-
Diameter of Cylinder
Diameter or Rod
cured, or field-cured. or Width of Beam
mm [in.]
mm [in.]
3 1
<150 [6] 10 ± 2 [ ⁄8 ± ⁄16 ]
5 1
Available from American Concrete Institute (ACI), P.O. Box 9094, Farmington $150 [6] 16 ± 2 [ ⁄8 ± ⁄16 ]
Hills, MI 48333-9094, http://www.aci-int.org.
C31/C31M − 24a
greater than the depth of the mold in which rodding is being to set in an upright position. The cylinder diameter shall be at
performed, but not greater than 600 mm [24 in.] in overall least 3 times the nominal maximum size of the coarse
length (see Note 3). The rod shall have the tamping end or both aggregate. The length of the cylinder shall be twice the
ends rounded to a hemispherical tip of the same diameter as the diameter of the cylinder. If the nominal maximum size of the
rod. aggregate is 37.5 mm [1 ⁄2 in. ] or larger, acceptance test
NOTE 3—A rod length of 400 mm [16 in.] to 600 mm [24 in.] meets the
specimens for compressive strength shall be 150 mm by 300
requirements of the following: Practice C31/C31M, Test Method C138/
mm [6 in. by 12 in.] cylinders. If the nominal maximum size of
C138M, Test Method C143/C143M, Test Method C173/C173M, and Test
the aggregate is less than 37.5 mm [1 ⁄2 in.], acceptance test
Method C231/C231M.
specimens for compressive strength shall be either 150 mm by
5.5 Vibrators—Internal vibrators shall be used. The vibrator
300 mm [6 in. by 12 in.] cylinders or 100 by 200 mm [4 in. by
frequency shall be at least 150 Hz [9000 vibrations per minute]
8 in.] cylinders.
while the vibrator is operating in the concrete. The diameter of
NOTE 5—See 7.2 for concrete containing coarse aggregate larger than
a round vibrator shall be no more than one-fourth the diameter
50 mm [2 in.] nominal maximum size.
of the cylinder mold or one-fourth the width of the beam mold.
NOTE 6—If molds in SI units are required and not available, molds of
Other shaped vibrators shall have a perimeter equivalent to the
equivalent size in inch-pound units should be permitted. If molds in
circumference of an appropriate round vibrator. The combined
inch-pound units are required and not available, molds of equivalent size
in SI units should be permitted.
length of the vibrator shaft and vibrating element shall exceed
the depth of the section being vibrated by at least 75 mm [3
6.2 Beam Specimens—Flexural strength specimens shall be
in.]. The vibrator frequency shall be checked periodically with
beams of concrete cast and hardened in the horizontal position.
a vibrating-reed tachometer or other suitable device.
The length shall be at least 50 mm [2 in.] greater than three
times the depth as tested. The ratio of width to depth as molded
NOTE 4—For information on size and frequency of various vibrators
shall not exceed 1.5.
and a method to periodically check vibrator frequency see ACI 309R.
6.2.1 The minimum cross-sectional dimension of the beam
5.6 Mallet—A mallet with a rubber or rawhide head weigh-
shall be as stated in Table 2. Unless otherwise specified by the
ing 0.6 kg 6 0.2 kg [1.25 lb 6 0.50 lb] shall be used.
specifier of tests, the standard beam shall be 150 mm by 150
5.7 Placement Tools—of a size large enough so each amount
mm [6 in. by 6 in.] in cross section.
of concrete obtained from the sampling receptacle is represen-
6.2.2 When the nominal maximum size of the coarse
tative and small enough so concrete is not spilled during
aggregate exceeds 50 mm [2 in.], the concrete sample shall be
placement in the mold. For placing concrete in a cylinder mold,
treated by wet sieving through a 50 mm [2 in.] sieve as
the acceptable tool is a scoop. For placing concrete in a beam
described in Practice C172/C172M.
mold, either a shovel or scoop is permitted.
6.2.3 The specifier of tests shall specify the specimen size
and the number of specimens to be tested to obtain an average
5.8 Finishing Tools—a handheld float or a trowel.
test result (Note 7). The same specimen size shall be used when
5.9 Slump Apparatus—The apparatus for measurement of
comparing results and for mixture qualification and acceptance
slump shall conform to the requirements of Test Method
testing.
C143/C143M.
NOTE 7—The modulus of rupture can be determined using different
5.10 Sampling Receptacle—The receptacle shall be a suit-
specimen sizes. However, measured modulus of rupture generally in-
able heavy gauge metal pan, wheelbarrow, or flat, clean 5,6
creases as specimen size decreases. The strength ratio for beams of
nonabsorbent board of sufficient capacity to allow easy remix-
different sizes depends primarily on the maximum size of aggregate.
ing of the entire sample with a shovel or trowel. Experimental data obtained in two different studies have shown that for
maximum aggregate size between 19.0 mm and 25.0 mm [ ⁄4 in. and 1 in.],
5.11 Air Content Apparatus—The apparatus for measuring
the ratio between the modulus of rupture determined with a 150 mm by
air content shall conform to the requirements of Test Methods
150 mm [6 in. by 6 in.] and a 100 mm by 100 mm [4 in. by 4 in.] may vary
C173/C173M or C231/C231M. from 0.90 to 1.07 and for maximum aggregate size between 9.5 mm and
3 1
37.5 mm [ ⁄8 in. and 1 ⁄2 in.], the ratio between the modulus of rupture
5.12 Temperature Measuring Devices—The temperature
determined with a 150 mm by 150 mm [6 in. by 6 in.] and a 115 mm by
measuring devices shall conform to the applicable require-
115 mm [4.5 in. by 4.5 in.] may vary from 0.86 to 1.00.
ments of Test Method C1064/C1064M.
Tanesi, J; Ardani, A. Leavitt, J. "Reducing the Specimen Size of Concrete
6. Testing Requirements
Flexural Strength Test (AASHTO T97) for Safety and Ease of Handling," Trans-
6.1 Cylindrical Specimens—Compressive or splitting- portation Research Record: Journal of the Transportation Research Board, No.
2342, Transportation Research Board of National Academies, Washington, D.C.,
tensile-strength specimens shall be cylinders cast and allowed
Carrasquillo, P.M. and Carrasquillo, R. L “Improved Concrete Quality Control
Procedures Using Third Point Loading”, Research Report 119-1F, Project 3-9-87-
1119, Center for Transportation Research, The University of Texas at Austin,
TABLE 2 Minimum Cross-Sectional Dimension of Beams
November 1987.
Carrasquillo, P.M. and Carrasquillo, R. L “Improved Concrete Quality Control
Nominal
Minimum
Procedures Using Third Point Loading”, Research Report 119-1F, Project 3-9-87-
Maximum
Cross-Sectional
1119, Center for Transportation Research, The University of Texas at Austin,
Aggregate
Dimension
November 1987.
Size (NMAS)
Bazant, Z. and Novak, D. "Proposal for Standard Test of Modulus of Rupture
# 25 mm [1 in.] 100 mm by 100 mm [4 in. by 4 in.]
25 mm [1 in.] < NMAS # 50 mm [2 in.] 150 mm by 150 mm [6 in. by 6 in.] of Concrete with its Size Dependence," ACI Materials Journal, January-February
2001.
C31/C31M − 24a
TABLE 4 Requirements for Consolidation by Rodding
6.3 Field Technicians—The field technicians making and
curing specimens for acceptance testing shall meet the person- Number of
Specimen Type Number of Layers of
Roddings
nel qualification requirements of Practice C1077.
and Size Approximately Equal Depth
per Layer
Cylinders:
7. Sampling Concrete
Diameter, mm [in.]
100 [4] 2 25
7.1 Sample the concrete in accordance with Practice C172/
150 [6] 3 25
C172M after all adjustments, including water and admixture
225 [9] 4 50
additions, have been made.
Beams:
7.2 If the nominal maximum size of the coarse aggregate
Width, mm [in.]
exceeds 50 mm [2 in.], wet sieve the concrete sample through
100 [4] to 2 see 9.4
200 [8]
a 50 mm [2 in.] sieve as described in Practice C172/C172M.
>200 [8] 3 or more equal depths, see 9.4
each not to exceed
7.3 Record the identification of the sample with respect to
150 mm [6 in.].
the location of the concrete represented and the time of casting.
8. Fresh Concrete Tests
TABLE 5 Requirements for Consolidation by Vibration
8.1 Perform the following tests for each sample of concrete
Number of
from which specimens are made for acceptance testing for
Specimen Type Number of Vibrator Approximate Depth of
strength: and Size Layers Insertions Layer, mm [in.]
per Layer
8.1.1 Slump or Slump Flow—After remixing the sample in
Cylinders:
the receptacle, measure and record the slump or slump flow in
Diameter, mm [in.]
accordance with Test Method C143/C143M or Test Method
100 [4] 2 1 one-half depth of specimen
150 [6] 2 2 one-half depth of specimen
C1611/C1611M, respectively.
225 [9] 2 4 one-half depth of specimen
8.1.2 Air Content—Determine and record the air content in
accordance with either Test Method C173/C173M or Test
Beams:
Method C231/C231M. The concrete used in performing the air Width, mm [in.]
100 [4] to 1 see 9.5.2 depth of specimen
content test shall not be used in fabricati
...

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: C31/C31M − 24 C31/C31M − 24a
Standard Practice for
Making and Curing Concrete Test Specimens in the Field
This standard is issued under the fixed designation C31/C31M; 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 (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope*
1.1 This practice covers procedures for making and curing cylinder and beam specimens from representative samples of fresh
concrete for a construction project.
1.2 This practice is not intended for making specimens from concrete not having measurable slump or requiring other sizes or
shapes of specimens.
1.3 This practice is not applicable to lightweight insulating concrete or controlled low strength material (CLSM).
NOTE 1—Test Method C495/C495M covers the preparation of specimens and the determination of the compressive strength of lightweight insulating
concrete. Test Method D4832 covers procedures for the preparation, curing, transporting and testing of cylindrical test specimens of CLSM.
1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each
system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the
two systems may result in non-conformance with the standard.
1.5 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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use. (Warning—Fresh hydraulic cementitious mixtures are caustic and may cause chemical burns
to exposed skin and tissue upon prolonged exposure. )
1.6 The text of this standard references notes which provide explanatory material. These notes shall not be considered as
requirements of the standard.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
This practice 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 Jan. 1, 2024April 1, 2024. Published February 2024April 2024. Originally approved in 1920. Last previous edition approved in 20232024 as
C31/C31M–23. DOI: 10.1520/C0031_C0031M-24.–24. DOI: 10.1520/C0031_C0031M-24A.
See Section on Safety Precautions, Manual of Aggregate and Concrete Testing, Annual Book of ASTM Standards, Vol. 04.02.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM 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
C31/C31M − 24a
C94/C94M Specification for Ready-Mixed Concrete
C125 Terminology Relating to Concrete and Concrete Aggregates
C138/C138M Test Method for Density (Unit Weight), Yield, and Air Content (Gravimetric) of Concrete
C143/C143M Test Method for Slump of Hydraulic-Cement Concrete
C172/C172M Practice for Sampling Freshly Mixed Concrete
C173/C173M Test Method for Air Content of Freshly Mixed Concrete by the Volumetric Method
C231/C231M Test Method for Air Content of Freshly Mixed Concrete by the Pressure Method
C330/C330M Specification for Lightweight Aggregates for Structural Concrete
C403/C403M Test Method for Time of Setting of Concrete Mixtures by Penetration Resistance
C470/C470M Specification for Molds for Forming Concrete Test Cylinders Vertically
C495/C495M Test Method for Compressive Strength of Lightweight Insulating Concrete
C511 Specification for Mixing Rooms, Moist Cabinets, Moist Rooms, and Water Storage Tanks Used in the Testing of Hydraulic
Cements and Concretes
C617/C617M Practice for Capping Cylindrical Concrete Specimens
C1064/C1064M Test Method for Temperature of Freshly Mixed Hydraulic-Cement Concrete
C1077 Practice for Agencies Testing Concrete and Concrete Aggregates for Use in Construction and Criteria for Testing Agency
Evaluation
C1611/C1611M Test Method for Slump Flow of Self-Consolidating Concrete
C1758/C1758M Practice for Fabricating Test Specimens with Self-Consolidating Concrete
D4832 Test Method for Preparation and Testing of Controlled Low Strength Material (CLSM) Cylindrical Test Specimens
2.2 American Concrete Institute Publication:
309R Guide for Consolidation of Concrete
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this practice, refer to Terminology C125.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 acceptance test specimens, n—standard-cured test specimens intended for evaluating whether the supplied concrete complies
with the specification.
3.2.2 field-curing, n—storing test specimens in the field under an environmental temperature and moisture environment similar to
the in-place concrete.
3.2.3 initial-curing, n—the storage of test specimens in the field after molding and before transporting the specimens to the
laboratory.
3.2.3.1 Discussion—
Initial curing covers the time period from molding to transporting the test specimens.
3.2.4 initial standard curing temperature, n—temperature of the environment surrounding the specimen during initial standard
curing.
3.2.4.1 Discussion—
The environment surrounding standard-cured test specimens may be air, water, or damp sand. The temperature of the environment
surrounding standard-cured test specimen might not be the same as the concrete temperature.
3.2.5 standard-curing, n—storing test specimens in an environment of a specified temperature range, and under conditions that
control the loss of moisture from the test specimens while the test specimens are in the field and while in the laboratory.
3.2.5.1 Discussion—
Standard-curing is intended to reduce the influence of variations by standardizing the temperature and moisture environment on
the strength development of test specimens. Standard-curing includes requirements for the curing environment while the test
specimens are in the field (10.1.2) and while the test specimens are in the laboratory (10.1.3).
Available from American Concrete Institute (ACI), P.O. Box 9094, Farmington Hills, MI 48333-9094, http://www.aci-int.org.
C31/C31M − 24a
4. Significance and Use
4.1 This practice provides standardized requirements for making, and curing test specimens in the field. This practice also provides
requirements for transporting test specimens to the laboratory, and for curing test specimens in the laboratory. Depending on their
purpose, test specimens are either standard-cured, or field-cured.
4.2 Uses of the test results of standard-cured test specimens include the following purposes:
4.2.1 Acceptance testing for specified concrete strength,
NOTE 2—Specification C94/C94M requires compressive-strength test specimens for acceptance to be standard-cured.
4.2.2 Checking adequacy of mixture proportions for concrete strength, and
4.2.3 Quality control.
4.3 Uses of test results of field-cured test specimens include:
4.3.1 Estimation of the in place concrete strength,
4.3.2 Comparison with test results of standard cured specimens or with test results from various in-place test methods,
4.3.3 Adequacy of curing and protection of concrete in the structure,
4.3.4 Form or shoring removal time requirements, or
4.3.5 Post-tensioning.
5. Apparatus
5.1 Molds, General—Molds for specimens or fastenings thereto in contact with the concrete shall be made of steel, cast iron, or
other nonabsorbent material, nonreactive with concrete containing portland or other hydraulic cements. Molds shall hold their
dimensions and shape under all conditions of use. Molds shall be watertight during use as judged by their ability to hold water
poured into them. Provisions for tests of water leakage are given in the Test Methods for Elongation, Absorption, and Water
Leakage section of Specification C470/C470M. A suitable sealant, such as heavy grease, modeling clay, or microcrystalline wax
shall be used where necessary to prevent leakage through the joints. Positive means shall be provided to hold base plates firmly
to the molds. Reusable molds shall be lightly coated with mineral oil or a suitable nonreactive form release material before use.
5.2 Cylinder Molds—Molds for casting concrete test specimens shall conform to the requirements of Specification C470/C470M.
Cardboard cylinder molds shall not be used for standard-cured specimens.
5.3 Beam Molds—Beam molds shall be of the shape and dimensions required to produce the specimens stipulated in 6.2. The
inside surfaces of the molds shall be smooth. The sides, bottom, and ends shall be at right angles to each other and shall be straight
and true and free of warpage. Maximum variation from the nominal cross section shall not exceed 3 mm [ ⁄8 in.] for molds with
depth or breadth of 150 mm [6 in.] or more. Molds shall produce specimens at least as long but not more than 2 mm [ ⁄16 in.] shorter
than the required length in 6.2.
5.4 Tamping Rod—A round, smooth, straight, steel rod with a diameter conforming to the requirements in Table 1. The length of
the tamping rod shall be at least 100 mm [4 in.] greater than the depth of the mold in which rodding is being performed, but not
TABLE 1 Tamping Rod Diameter Requirements
Diameter of Cylinder
Diameter or Rod
or Width of Beam
mm [in.]
mm [in.]
3 1
<150 [6] 10 ± 2 [ ⁄8 ± ⁄16 ]
5 1
$150 [6] 16 ± 2 [ ⁄8 ± ⁄16 ]
C31/C31M − 24a
greater than 600 mm [24 in.] in overall length (see Note 3). The rod shall have the tamping end or both ends rounded to a
hemispherical tip of the same diameter as the rod.
NOTE 3—A rod length of 400 mm [16 in.] to 600 mm [24 in.] meets the requirements of the following: Practice C31/C31M, Test Method C138/C138M,
Test Method C143/C143M, Test Method C173/C173M, and Test Method C231/C231M.
5.5 Vibrators—Internal vibrators shall be used. The vibrator frequency shall be at least 150 Hz [9000 vibrations per minute] while
the vibrator is operating in the concrete. The diameter of a round vibrator shall be no more than one-fourth the diameter of the
cylinder mold or one-fourth the width of the beam mold. Other shaped vibrators shall have a perimeter equivalent to the
circumference of an appropriate round vibrator. The combined length of the vibrator shaft and vibrating element shall exceed the
depth of the section being vibrated by at least 75 mm [3 in.]. The vibrator frequency shall be checked periodically with a
vibrating-reed tachometer or other suitable device.
NOTE 4—For information on size and frequency of various vibrators and a method to periodically check vibrator frequency see ACI 309R.
5.6 Mallet—A mallet with a rubber or rawhide head weighing 0.6 kg 6 0.2 kg [1.25 lb 6 0.50 lb] shall be used.
5.7 Placement Tools—of a size large enough so each amount of concrete obtained from the sampling receptacle is representative
and small enough so concrete is not spilled during placement in the mold. For placing concrete in a cylinder mold, the acceptable
tool is a scoop. For placing concrete in a beam mold, either a shovel or scoop is permitted.
5.8 Finishing Tools—a handheld float or a trowel.
5.9 Slump Apparatus—The apparatus for measurement of slump shall conform to the requirements of Test Method C143/C143M.
5.10 Sampling Receptacle—The receptacle shall be a suitable heavy gauge metal pan, wheelbarrow, or flat, clean nonabsorbent
board of sufficient capacity to allow easy remixing of the entire sample with a shovel or trowel.
5.11 Air Content Apparatus—The apparatus for measuring air content shall conform to the requirements of Test Methods
C173/C173M or C231/C231M.
5.12 Temperature Measuring Devices—The temperature measuring devices shall conform to the applicable requirements of Test
Method C1064/C1064M.
6. Testing Requirements
6.1 Cylindrical Specimens—Compressive or splitting-tensile-strength specimens shall be cylinders cast and allowed to set in an
upright position. The cylinder diameter shall be at least 3 times the nominal maximum size of the coarse aggregate. The length
of the cylinder shall be twice the diameter of the cylinder. If the nominal maximum size of the aggregate is 37.5 mm [1 ⁄2 in. ] or
larger, acceptance test specimens for compressive strength shall be 150 mm by 300 mm [6 in. by 12 in.] cylinders. If the nominal
maximum size of the aggregate is less than 37.5 mm [1 ⁄2 in.], acceptance test specimens for compressive strength shall be either
150 mm by 300 mm [6 in. by 12 in.] cylinders or 100 by 200 mm [4 in. by 8 in.] cylinders.
NOTE 5—See 7.2 for concrete containing coarse aggregate larger than 50 mm [2 in.] nominal maximum size.
NOTE 6—If molds in SI units are required and not available, molds of equivalent size in inch-pound units should be permitted. If molds in inch-pound
units are required and not available, molds of equivalent size in SI units should be permitted.
TABLE 2 Minimum Cross-Sectional Dimension of Beams
Nominal
Minimum
Maximum
Cross-Sectional
Aggregate
Dimension
Size (NMAS)
# 25 mm [1 in.] 100 mm by 100 mm [4 in. by 4 in.]
25 mm [1 in.] < NMAS # 50 mm [2 in.] 150 mm by 150 mm [6 in. by 6 in.]
C31/C31M − 24a
6.2 Beam Specimens—Flexural strength specimens shall be beams of concrete cast and hardened in the horizontal position. The
length shall be at least 50 mm [2 in.] greater than three times the depth as tested. The ratio of width to depth as molded shall not
exceed 1.5.
6.2.1 The minimum cross-sectional dimension of the beam shall be as stated in Table 2. Unless otherwise specified by the specifier
of tests, the standard beam shall be 150 mm by 150 mm [6 in. by 6 in.] in cross section.
6.2.2 When the nominal maximum size of the coarse aggregate exceeds 50 mm [2 in.], the concrete sample shall be treated by
wet sieving through a 50 mm [2 in.] sieve as described in Practice C172/C172M.
6.2.3 The specifier of tests shall specify the specimen size and the number of specimens to be tested to obtain an average test result
(Note 7). The same specimen size shall be used when comparing results and for mixture qualification and acceptance testing.
NOTE 7—The modulus of rupture can be determined using different specimen sizes. However, measured modulus of rupture generally increases as
5,6 7
specimen size decreases. The strength ratio for beams of different sizes depends primarily on the maximum size of aggregate. Experimental data
obtained in two different studies have shown that for maximum aggregate size between 19.0 mm and 25.0 mm [ ⁄4 in. and 1 in.], the ratio between the
modulus of rupture determined with a 150 mm by 150 mm [6 in. by 6 in.] and a 100 mm by 100 mm [4 in. by 4 in.] may vary from 0.90 to 1.07 and
3 1
for maximum aggregate size between 9.5 mm and 37.5 mm [ ⁄8 in. and 1 ⁄2 in.], the ratio between the modulus of rupture determined with a 150 mm by
150 mm [6 in. by 6 in.] and a 115 mm by 115 mm [4.5 in. by 4.5 in.] may vary from 0.86 to 1.00.
6.3 Field Technicians—The field technicians making and curing specimens for acceptance testing shall meet the personnel
qualification requirements of Practice C1077.
7. Sampling Concrete
7.1 Sample the concrete in accordance with Practice C172/C172M after all adjustments, including water and admixture additions,
have been made.
7.2 If the nominal maximum size of the coarse aggregate exceeds 50 mm [2 in.], wet sieve the concrete sample through a 50 mm
[2 in.] sieve as described in Practice C172/C172M.
7.3 Record the identification of the sample with respect to the location of the concrete represented and the time of casting.
8. Fresh Concrete Tests
8.1 Perform the following tests for each sample of concrete from which specimens are made for acceptance testing for strength:
8.1.1 Slump or Slump Flow—After remixing the sample in the receptacle, measure and record the slump or slump flow in
accordance with Test Method C143/C143M or Test Method C1611/C1611M, respectively.
8.1.2 Air Content—Determine and record the air content in accordance with either Test Method C173/C173M or Test Method
C231/C231M. The concrete used in performing the air content test shall not be used in fabricating test specimens.
8.1.3 Temperature—Determine and record the temperature in accordance with Test Method C1064/C1064M.
NOTE 8—Some specifications may require the measurement of the unit weight of concrete. The volume of concrete produced per batch may be desired
on some projects. Also, additional information on the air content measurements may be desired. Test Method C138/C138M is used to measure the unit
weight, yield, and gravimetric air content of freshly mixed concrete.
Tanesi, J; Ardani, A. Leavitt, J. "Reducing the Specimen Size of Concrete Flexural Strength Test (AASHTO T97) for Safety and Ease of Handling," Transportation
Research Record: Journal of the Transportation Research Board, No. 2342, Transportation Research Board of National Academies, Washington, D.C., Carrasquillo, P.M. and
Carrasquillo, R. L “Improved Concrete Quality Control Procedures Using Third Point Loading”, Research Report 119-1F, Project 3-9-87-1119, Center for Transportation
Research, The University of Texas at Austin, November 1987.
Carrasquillo, P.M. and Carrasquillo, R. L “Improved Concrete Quality Control Procedures Using Third Point Loading”, Research Report 119-1F, Project 3-9-87-1119,
Center for Transportation Research, The University of Texas at Austin, November 1987.
Bazant, Z. and Novak, D. "Proposal for Standard Test of Modulus of Rupture of Concrete with its Size Dependence," ACI Materials Journal, January-February 2001.
C31/C31M − 24a
9. MoldingCasting Specimens
9.1 Place of Molding—Mold specimens promptly on a level, rigid surface, free of vibration and other disturbances, at a place as
near as practicable to the location where they are to be stored.
9.2 Self-Consolidating Concrete—If casting a specimen of self-
...