ASTM C39/C39M-23

Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens

SIGNIFICANCE AND USE
5.1 Care must be exercised in the interpretation of the significance of compressive strength determinations by this test method since strength is not a fundamental or intrinsic property of concrete made from given materials. Values obtained will depend on the size and shape of the specimen, batching, mixing procedures, the methods of sampling, molding, and fabrication and the age, temperature, and moisture conditions during curing.  
5.2 This test method is used to determine compressive strength of cylindrical specimens prepared and cured in accordance with Practices C31/C31M, C192/C192M, C617/C617M, C943, C1176/C1176M, C1231/C1231M, and C1435/C1435M, and Test Methods C42/C42M, C873/C873M, and C1604/C1604M.  
5.3 The results of this test method are used as a basis for quality control of concrete proportioning, mixing, and placing operations; determination of compliance with specifications; control for evaluating effectiveness of admixtures; and similar uses.  
5.4 The individual who tests concrete cylinders for acceptance testing shall meet the concrete laboratory technician requirements of Practice C1077, including an examination requiring performance demonstration that is evaluated by an independent examiner.
Note 1: Certification equivalent to the minimum guidelines for ACI Concrete Laboratory Technician, Level I or ACI Concrete Strength Testing Technician will satisfy this requirement.
SCOPE
1.1 This test method covers determination of compressive strength of cylindrical concrete specimens such as molded cylinders and drilled cores. It is limited to concrete having a density in excess of 800 kg/m3 [50 lb/ft3].  
1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The inch-pound units are shown in brackets. 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.  
1.3 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.(Warning—Means should be provided to contain concrete fragments during sudden rupture of specimens. Tendency for sudden rupture increases with increasing concrete strength and it is more likely when the testing machine is relatively flexible. The safety precautions given in R0030 are recommended.)  
1.4 The text of this standard references notes which provide explanatory material. These notes shall not be considered as requirements of the standard.  
1.5 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: 30-Nov-2023
• 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 C39/C39M-21 - Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens
• Effective Date: 01-Dec-2023
• Refers: ASTM C31/C31M-24a - Standard Practice for Making and Curing Concrete Test Specimens in the Field
• Effective Date: 01-Apr-2024
• Refers: ASTM C670-24a - Standard Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials
• Effective Date: 01-Feb-2024
• Refers: ASTM C1077-24 - Standard Practice for Agencies Testing Concrete and Concrete Aggregates for Use in Construction and Criteria for Testing Agency Evaluation
• Effective Date: 01-Jan-2024
• Refers: ASTM C31/C31M-24 - Standard Practice for Making and Curing Concrete Test Specimens in the Field
• Effective Date: 01-Jan-2024
• Refers: ASTM C670-24 - Standard Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials
• Effective Date: 01-Jan-2024
• Refers: ASTM C31/C31M-23 - Standard Practice for Making and Curing Concrete Test Specimens in the Field
• Effective Date: 01-Jun-2023
• Refers: ASTM C1231/C1231M-15 - Standard Practice for Use of Unbonded Caps in Determination of Compressive Strength of Hardened Cylindrical Concrete Specimens
• Effective Date: 01-Dec-2015
• Refers: ASTM C670-15 - Standard Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials
• Effective Date: 15-Jun-2015
• Refers: ASTM C617/C617M-15 - Standard Practice for Capping Cylindrical Concrete Specimens
• Effective Date: 01-Apr-2015
• Referred By: ASTM C1903-21 - Standard Specification for Precast Concrete Duct Bank
• Effective Date: 01-Dec-2023
• Referred By: ASTM C918/C918M-20 - Standard Test Method for Measuring Early-Age Compressive Strength and Projecting Later-Age Strength
• Effective Date: 01-Dec-2023
• Referred By: ASTM C330/C330M-23 - Standard Specification for Lightweight Aggregates for Structural Concrete
• Effective Date: 01-Dec-2023
• Referred By: ASTM D7147-21 - Standard Specification for Testing and Establishing Allowable Loads of Joist Hangers
• Effective Date: 01-Dec-2023
• Referred By: ASTM C497M-20a - Standard Test Methods for Concrete Pipe, Concrete Box Sections, Manhole Sections, or Tile (Metric)
• Effective Date: 01-Dec-2023

Overview

ASTM C39/C39M-23 is the internationally recognized standard test method for determining the compressive strength of cylindrical concrete specimens. Issued by ASTM International, this standard specifies procedures for assessing concrete quality and is widely used in construction, quality control, and research applications. The document covers testing both molded cylinders and drilled cores with a density greater than 800 kg/m³, using either SI or inch-pound units.

Compressive strength testing provides essential data for verifying structural performance, proportioning of concrete mixes, and compliance with construction specifications. Since compressive strength is influenced by various production and testing variables, the standard emphasizes careful interpretation of results.

Key Topics

• Specimen Preparation and Curing
  The standard applies to specimens that have been prepared and cured following referenced ASTM practices, such as C31/C31M, C192/C192M, C617/C617M, and others.
• Testing Apparatus and Calibration
  Requirements for testing machines, calibration procedures, and apparatus, including specifications for bearing blocks and load indication systems.
• Loading Procedure
  Step-by-step instructions for applying axial load to a specimen, calculating compressive strength, accounting for specimen dimensions, and using correction factors for different length-to-diameter ratios.
• Result Interpretation
  Emphasizes that compressive strength results depend on variables like specimen size, shape, curing conditions, and preparation methods. Care is needed to correlate test results with field performance.
• Technician Qualification
  Individuals performing acceptance testing must meet specific competency and certification criteria (e.g., ACI Concrete Strength Testing Technician).

Applications

ASTM C39/C39M-23 is essential for a range of concrete-related activities, delivering practical benefits in the following areas:

• Quality Control in Concrete Construction
  Ensures that concrete delivered to job sites meets specified strength requirements, contributing to reliable, long-lasting structures.
• Proportioning and Mix Design Validation
  Assesses whether concrete mixes produce the required strength for their intended application.
• Compliance with Project Specifications
  Used by engineers, contractors, and testing agencies to verify that placed concrete conforms to contractual and regulatory strength requirements.
• Admixture Evaluation
  Evaluates the effectiveness of chemical and mineral admixtures by comparing the compressive strength of modified mixes to control samples.
• Research and Development
  Provides data to support innovation in concrete technology, new material formulations, and construction techniques.

Related Standards

ASTM C39/C39M-23 references and is complemented by several related documents, helping ensure uniformity and accuracy in concrete testing:

• ASTM C31/C31M – Making and Curing Concrete Test Specimens in the Field
• ASTM C42/C42M – Obtaining and Testing Drilled Cores and Sawed Beams of Concrete
• ASTM C617/C617M – Capping Cylindrical Concrete Specimens
• ASTM C192/C192M – Making and Curing Concrete Test Specimens in the Laboratory
• ASTM C1077 – Agencies Testing Concrete and Concrete Aggregates for Use in Construction
• ASTM C125 – Terminology Relating to Concrete and Concrete Aggregates
• ASTM C1231/C1231M – Use of Unbonded Caps in Determination of Compressive Strength
• ASTM E4 – Practices for Force Calibration and Verification of Testing Machines
• ASTM C943, C1176/C1176M, C1435/C1435M, C1604/C1604M, C873/C873M – Various practices for preparing, curing, and testing concrete specimens.

For comprehensive quality assurance, practitioners are encouraged to consult applicable referenced standards alongside ASTM C39/C39M-23.

---

By following ASTM C39/C39M-23, organizations ensure consistent, reliable measurements of compressive strength, supporting greater safety, compliance, and quality in concrete construction projects. This standard is indispensable for engineers, laboratory technicians, and construction professionals focused on concrete performance and regulatory compliance.

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: C39/C39M − 23
Standard Test Method for
Compressive Strength of Cylindrical Concrete Specimens
This standard is issued under the fixed designation C39/C39M; 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* 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method covers determination of compressive
C31/C31M Practice for Making and Curing Concrete Test
strength of cylindrical concrete specimens such as molded
Specimens in the Field
cylinders and drilled cores. It is limited to concrete having a
3 3
C42/C42M Test Method for Obtaining and Testing Drilled
density in excess of 800 kg/m [50 lb/ft ].
Cores and Sawed Beams of Concrete
1.2 The values stated in either SI units or inch-pound units
C125 Terminology Relating to Concrete and Concrete Ag-
are to be regarded separately as standard. The inch-pound units
gregates
are shown in brackets. The values stated in each system may
C192/C192M Practice for Making and Curing Concrete Test
not be exact equivalents; therefore, each system shall be used
Specimens in the Laboratory
independently of the other. Combining values from the two
C617/C617M Practice for Capping Cylindrical Concrete
systems may result in non-conformance with the standard.
Specimens
C670 Practice for Preparing Precision and Bias Statements
1.3 This standard does not purport to address all of the
for Test Methods for Construction Materials
safety concerns, if any, associated with its use. It is the
C873/C873M Test Method for Compressive Strength of
responsibility of the user of this standard to establish appro-
Concrete Cylinders Cast in Place in Cylindrical Molds
priate safety, health, and environmental practices and deter-
C943 Practice for Making Test Cylinders and Prisms for
mine the applicability of regulatory limitations prior to
Determining Strength and Density of Preplaced-
use.(Warning—Means should be provided to contain concrete
Aggregate Concrete in the Laboratory
fragments during sudden rupture of specimens. Tendency for
C1077 Practice for Agencies Testing Concrete and Concrete
sudden rupture increases with increasing concrete strength and
Aggregates for Use in Construction and Criteria for
it is more likely when the testing machine is relatively flexible.
Testing Agency Evaluation
The safety precautions given in R0030 are recommended.)
C1176/C1176M Practice for Making Roller-Compacted
1.4 The text of this standard references notes which provide
Concrete in Cylinder Molds Using a Vibrating Table
explanatory material. These notes shall not be considered as
C1231/C1231M Practice for Use of Unbonded Caps in
requirements of the standard.
Determination of Compressive Strength of Hardened Cy-
lindrical Concrete Specimens
1.5 This international standard was developed in accor-
C1435/C1435M Practice for Molding Roller-Compacted
dance with internationally recognized principles on standard-
Concrete in Cylinder Molds Using a Vibrating Hammer
ization established in the Decision on Principles for the
C1604/C1604M Test Method for Obtaining and Testing
Development of International Standards, Guides and Recom-
Drilled Cores of Shotcrete
mendations issued by the World Trade Organization Technical
E4 Practices for Force Calibration and Verification of Test-
Barriers to Trade (TBT) Committee.
ing Machines
E18 Test Methods for Rockwell Hardness of Metallic Ma-
terials
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. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Dec. 1, 2023. Published December 2023. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1921. Last previous edition approved in 2021 as C39/C39M – 21. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/C0039_C0039M-23. 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
C39/C39M − 23
E74 Practices for Calibration and Verification for Force- C943, C1176/C1176M, C1231/C1231M, and C1435/C1435M,
Measuring Instruments and Test Methods C42/C42M, C873/C873M, and C1604/
R0030 Manual of Aggregate and Concrete Testing C1604M.
5.3 The results of this test method are used as a basis for
3. Terminology
quality control of concrete proportioning, mixing, and placing
3.1 Definitions—For definitions of terms used in this operations; determination of compliance with specifications;
practice, refer to Terminology C125. control for evaluating effectiveness of admixtures; and similar
uses.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 bearing block, n—steel piece to distribute the load 5.4 The individual who tests concrete cylinders for accep-
from the testing machine to the specimen. tance testing shall meet the concrete laboratory technician
requirements of Practice C1077, including an examination
3.2.2 lower bearing block, n—steel piece placed under the
requiring performance demonstration that is evaluated by an
specimen to distribute the load from the testing machine to the
independent examiner.
specimen.
3.2.2.1 Discussion—The lower bearing block provides a
NOTE 1—Certification equivalent to the minimum guidelines for ACI
Concrete Laboratory Technician, Level I or ACI Concrete Strength
readily machinable surface for maintaining the specified bear-
Testing Technician will satisfy this requirement.
ing surface. The lower bearing block may also be used to adapt
the testing machine to various specimen heights. The lower
6. Apparatus
bearing block is also referred to as bottom block, plain block,
and false platen.
6.1 Testing Machine—The testing machine shall be of a type
having sufficient capacity and capable of providing the rates of
3.2.3 platen, n—primary bearing surface of the testing
loading prescribed in 8.5.
machine.
6.1.1 Verify the accuracy of the testing machine in accor-
3.2.3.1 Discussion—The platen is also referred to as the
dance with Practices E4, except that the verified loading range
testing machine table.
shall be as required in 6.4. Verification is required:
3.2.4 spacer, n—steel piece used to elevate the lower bear-
6.1.1.1 Within 13 months of the last calibration,
ing block to accommodate test specimens of various heights.
6.1.1.2 On original installation or immediately after
3.2.4.1 Discussion—Spacers are not required to have hard-
relocation,
ened bearing faces because spacers are not in direct contact
6.1.1.3 Immediately after making repairs or adjustments
with the specimen or the retainers of unbonded caps.
that affect the operation of the force applying system or the
3.2.5 upper bearing block, n—steel assembly suspended
values displayed on the load indicating system, except for zero
above the specimen that is capable of tilting to bear uniformly
adjustments that compensate for the mass of bearing blocks or
on the top of the specimen.
specimen, or both, or
3.2.5.1 Discussion—The upper bearing block is also re-
6.1.1.4 Whenever there is reason to suspect the accuracy of
ferred to as the spherically seated block and the suspended
the indicated loads.
block.
6.1.2 Design—The design of the machine must include the
following features:
4. Summary of Test Method
6.1.2.1 The machine must be power operated and must
4.1 This test method consists of applying a compressive
apply the load continuously rather than intermittently, and
axial load to molded cylinders or cores at a rate which is within
without shock. If it has only one loading rate (meeting the
a prescribed range until failure occurs. The compressive
requirements of 8.5), it must be provided with a supplemental
strength of the specimen is calculated by dividing the maxi-
means for loading at a rate suitable for verification. This
mum load attained during the test by the cross-sectional area of
supplemental means of loading may be power or hand oper-
the specimen.
ated.
6.1.2.2 The space provided for test specimens shall be large
5. Significance and Use
enough to accommodate, in a readable position, an elastic
calibration device which is of sufficient capacity to cover the
5.1 Care must be exercised in the interpretation of the
potential loading range of the testing machine and which
significance of compressive strength determinations by this test
complies with the requirements of Practice E74.
method since strength is not a fundamental or intrinsic property
of concrete made from given materials. Values obtained will
NOTE 2—The types of elastic calibration devices most generally
depend on the size and shape of the specimen, batching, mixing
available and most commonly used for this purpose are the circular
procedures, the methods of sampling, molding, and fabrication proving ring or load cell.
and the age, temperature, and moisture conditions during
6.1.3 Accuracy—The accuracy of the testing machine shall
curing.
be in accordance with the following provisions:
5.2 This test method is used to determine compressive 6.1.3.1 The percentage of error for the loads within the
strength of cylindrical specimens prepared and cured in accor- proposed range of use of the testing machine shall not exceed
dance with Practices C31/C31M, C192/C192M, C617/C617M, 61.0 % of the indicated load.
C39/C39M − 23
6.1.3.2 The accuracy of the testing machine shall be verified 6.2 Bearing Blocks—The upper and lower bearing blocks
by applying five test loads in four approximately equal shall conform to the following requirements:
increments in ascending order. The difference between any two
6.2.1 Bearing blocks shall be steel with hardened bearing
successive test loads shall not exceed one third of the differ-
faces (Note 3).
ence between the maximum and minimum test loads.
6.2.2 Bearing faces shall have dimensions at least 3 %
6.1.3.3 The test load as indicated by the testing machine and
greater than the nominal diameter of the specimen.
the applied load computed from the readings of the verification
6.2.3 Except for the inscribed concentric circles described
device shall be recorded at each test point. Calculate the error,
in 6.2.4.7, the bearing faces shall not depart from a plane by
E, and the percentage of error, E , for each point from these
p
more than 0.02 mm [0.001 in.] along any 150 mm [6 in.] length
data as follows:
for bearing blocks with a diameter of 150 mm [6 in.] or larger,
or by more than 0.02 mm [0.001 in.] in any direction of smaller
E 5 A 2 B (1)
bearing blocks. New bearing blocks shall be manufactured
E 5 100~A 2 B!/B
p within one half of this tolerance.
where:
NOTE 3—It is desirable that the bearing faces of bearing blocks have a
Rockwell hardness at least 55 HRC as determined by Test Methods E18.
A = load, kN [lbf] indicated by the machine being verified,
NOTE 4—Square bearing faces are permissible for the bearing blocks.
and
B = applied load, kN [lbf] as determined by the calibrating
6.2.4 Upper Bearing Block—The upper bearing block shall
device.
conform to the following requirements:
6.1.3.4 The report on the verification of a testing machine
6.2.4.1 The upper bearing block shall be spherically seated
shall state within what loading range it was found to conform and the center of the sphere shall coincide with the center of the
to specification requirements rather than reporting a blanket bearing face within 65 % of the radius of the sphere.
acceptance or rejection. In no case shall the loading range be
6.2.4.2 The ball and the socket shall be designed so that the
stated as including loads below the value which is 100 times
steel in the contact area does not permanently deform when
the smallest change of load estimable on the load-indicating
loaded to the capacity of the testing machine.
mechanism of the testing machine or loads within that portion
NOTE 5—The preferred contact area is in the form of a ring (described
of the range below 10 % of the maximum range capacity.
as preferred bearing area) as shown in Fig. 1.
6.1.3.5 In no case shall the loading range be stated as
6.2.4.3 Provision shall be made for holding the upper
including loads outside the range of loads applied during the
bearing block in the socket. The design shall be such that the
verification test.
bearing face can be rotated and tilted at least 4° in any
6.1.3.6 The indicated load of a testing machine shall not be
direction.
corrected either by calculation or by the use of a calibration
6.2.4.4 If the upper bearing block is a two-piece design
diagram to obtain values within the required permissible
composed of a spherical portion and a bearing plate, a
variation.
mechanical means shall be provided to ensure that the spherical
portion is fixed and centered on the bearing plate.
6.2.4.5 The diameter of the sphere shall be at least 75 % of
the nominal diameter of the specimen. If the diameter of the
sphere is smaller than the diameter of the specimen, the portion
of the bearing face extending beyond the sphere shall have a
thickness not less than the difference between the radius of the
sphere and radius of the specimen (see Fig. 1). The least
dimension of the bearing face shall be at least as great as the
diameter of the sphere.
6.2.4.6 The dimensions of the bearing face of the upper
bearing block shall not exceed the following values:
Nominal Diameter Maximum Diameter Maximum Dimensions
of Specimen, of Round Bearing of Square Bearing
mm [in.] Face, mm [in.] Face, mm [in.]
50 [2] 105 [4] 105 by 105 [4 by 4]
75 [3] 130 [5] 130 by 130 [5 by 5]
100 [4] 165 [6.5] 165 by 165 [6.5 by 6.5]
150 [6] 255 [10] 255 by 255 [10 by 10]
200 [8] 280 [11] 280 by 280 [11 by 11]
6.2.4.7 If the diameter of the bearing face of the upper
T ≥ R – r
bearing block exceeds the nominal diameter of the specimen by
r = radius of spherical portion of upper bearing block
more than 13 mm [0.5 in.], concentric circles not more than 0.8
R = nominal radius of specimen
mm [0.03 in.] deep and not more than 1 mm [0.04 in.] wide
T = thickness of upper bearing block extending beyond the
shall be inscribed on the face of upper bearing block to
sphere
FIG. 1 Schematic Sketch of Typical Upper Bearing Block facilitate proper centering.
C39/C39M − 23
6.2.4.8 At least every six months, or as specified by the exceed the clear distance between the smallest graduations.
manufacturer of the testing machine, clean and lubricate the The scale shall be provided with a labeled graduation line load
curved surfaces of the socket and of the spherical portion of the corresponding to zero load. Each dial shall be equipped with a
upper bearing block. The lubricant shall be a petroleum-type zero adjustment located outside the dial case and accessible
oil such as conventional motor oil or as specified by the from the front of the machine while observing the zero mark
manufacturer of the testing machine. and dial pointer.
NOTE 6—To ensure uniform seating, the upper bearing block is NOTE 9—Readability is considered to be 0.5 mm [0.02 in.] along the arc
designed to tilt freely as it comes into contact with the top of the specimen. described by the end of the pointer. If the spacing is between 1 mm and
After contact, further rotation is undesirable. Friction between the socket 2 mm [0.04 in. and 0.08 in.], one half of a scale interval is considered
and the spherical portion of the head provides restraint against further readable. If the spacing is between 2 mm and 3 mm [0.08 in. and 0.12 in.],
rotation during loading. Pressure-type greases can reduce the desired one third of a scale interval is considered readable. If the spacing is 3 mm
friction and permit undesired rotation of the spherical head and should not [0.12 in.] or more, one fourth of a scale interval is considered readable.
be used unless recommended by the manufacturer of the testing machine.
6.4.4 If the load is displayed in digital form, the numbers
Petroleum-type oil such as conventional motor oil has been shown to
must be large enough to be read. The numerical increment shall
permit the necessary friction to develop.
not exceed 0.1 % of the full scale load of a given loading range.
6.2.5 Lower Bearing Block—The lower bearing block shall
Provision shall be made for adjusting the display to indicate a
conform to the following requirements:
value of zero when no load is applied to the specimen.
6.2.5.1 The lower bearing block shall be solid.
6.5 Documentation of the calibration and maintenance of
6.2.5.2 The top and bottom surfaces of the lower bearing
block shall be parallel to each other. the testing machine shall be in accordance with Practice
C1077.
6.2.5.3 The lower bearing block shall be at least 25 mm
[1.0 in.] thick when new, and at least 22.5 mm [0.9 in.] thick
after resurfacing. 7. Specimens
6.2.5.4 The lower bearing block shall be fully supported by
7.1 Specimens shall not be tested if any individual diameter
the platen of the testing machine or by any spacers used.
of a cylinder differs from any other diameter of the same
6.2.5.5 If the testing machine is designed that the platen
cylinder by more than 2 %.
itself is readily maintained in the specified surface condition, a
NOTE 10—This may occur when single use molds are damaged or
lower bearing block is not required.
deformed during shipment, when flexible single use molds are deformed
NOTE 7—The lower bearing block may be fastened to the platen of the during molding, or when a core drill deflects or shifts during drilling.
testing machine.
7.2 Prior to testing, neither end of test specimens shall
NOTE 8—Inscribed concentric circles as described in 6.2.4.7 are
depart from perpendicularity to the axis by more than
...

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: C39/C39M − 21 C39/C39M − 23
Standard Test Method for
Compressive Strength of Cylindrical Concrete Specimens
This standard is issued under the fixed designation C39/C39M; 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 test method covers determination of compressive strength of cylindrical concrete specimens such as molded cylinders and
3 3
drilled cores. It is limited to concrete having a density in excess of 800 kg/m [50 lb/ft ].
1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The inch-pound units are
shown in brackets. 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.
1.3 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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.(Warning—Means should be provided to contain concrete fragments during sudden rupture of
specimens. Tendency for sudden rupture increases with increasing concrete strength and it is more likely when the testing machine
is relatively flexible. The safety precautions given in R0030 are recommended.)
1.4 The text of this standard references notes which provide explanatory material. These notes shall not be considered as
requirements of the standard.
1.5 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:
C31/C31M Practice for Making and Curing Concrete Test Specimens in the Field
C42/C42M Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete
C125 Terminology Relating to Concrete and Concrete Aggregates
C192/C192M Practice for Making and Curing Concrete Test Specimens in the Laboratory
C617/C617M Practice for Capping Cylindrical Concrete Specimens
C670 Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials
C873/C873M Test Method for Compressive Strength of Concrete Cylinders Cast in Place in Cylindrical Molds
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 March 1, 2021Dec. 1, 2023. Published March 2021December 2023. Originally approved in 1921. Last previous edition approved in 20202021
as C39/C39M – 20.C39/C39M – 21. DOI: 10.1520/C0039_C0039M-21.10.1520/C0039_C0039M-23.
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*A Summary of Changes section appears at the end of this standard
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C943 Practice for Making Test Cylinders and Prisms for Determining Strength and Density of Preplaced-Aggregate Concrete
in the Laboratory
C1077 Practice for Agencies Testing Concrete and Concrete Aggregates for Use in Construction and Criteria for Testing Agency
Evaluation
C1176/C1176M Practice for Making Roller-Compacted Concrete in Cylinder Molds Using a Vibrating Table
C1231/C1231M Practice for Use of Unbonded Caps in Determination of Compressive Strength of Hardened Cylindrical
Concrete Specimens
C1435/C1435M Practice for Molding Roller-Compacted Concrete in Cylinder Molds Using a Vibrating Hammer
C1604/C1604M Test Method for Obtaining and Testing Drilled Cores of Shotcrete
E4 Practices for Force Calibration and Verification of Testing Machines
E18 Test Methods for Rockwell Hardness of Metallic Materials
E74 Practices for Calibration and Verification for Force-Measuring Instruments
R0030 Manual of Aggregate and Concrete Testing
3. Terminology
3.1 Definitions—For definitions of terms used in this practice, refer to Terminology C125.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 bearing block, n—steel piece to distribute the load from the testing machine to the specimen.
3.2.2 lower bearing block, n—steel piece placed under the specimen to distribute the load from the testing machine to the
specimen.
3.2.2.1 Discussion—
The lower bearing block provides a readily machinable surface for maintaining the specified bearing surface. The lower bearing
block may also be used to adapt the testing machine to various specimen heights. The lower bearing block is also referred to as
bottom block,plain block, and false platen.
3.2.3 platen, n—primary bearing surface of the testing machine.
3.2.3.1 Discussion—
The platen is also referred to as the testing machine table.
3.2.4 spacer, n—steel piece used to elevate the lower bearing block to accommodate test specimens of various heights.
3.2.4.1 Discussion—
Spacers are not required to have hardened bearing faces because spacers are not in direct contact with the specimen or the retainers
of unbonded caps.
3.2.5 upper bearing block, n—steel assembly suspended above the specimen that is capable of tilting to bear uniformly on the top
of the specimen.
3.2.5.1 Discussion—
The upper bearing block is also referred to as the spherically seated block and the suspended block.
4. Summary of Test Method
4.1 This test method consists of applying a compressive axial load to molded cylinders or cores at a rate which is within a
prescribed range until failure occurs. The compressive strength of the specimen is calculated by dividing the maximum load
attained during the test by the cross-sectional area of the specimen.
5. Significance and Use
5.1 Care must be exercised in the interpretation of the significance of compressive strength determinations by this test method
since strength is not a fundamental or intrinsic property of concrete made from given materials. Values obtained will depend on
the size and shape of the specimen, batching, mixing procedures, the methods of sampling, molding, and fabrication and the age,
temperature, and moisture conditions during curing.
5.2 This test method is used to determine compressive strength of cylindrical specimens prepared and cured in accordance with
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Practices C31/C31M, C192/C192M, C617/C617M, C943, C1176/C1176M, C1231/C1231M, and C1435/C1435M, and Test
Methods C42/C42M, C873/C873M, and C1604/C1604M.
5.3 The results of this test method are used as a basis for quality control of concrete proportioning, mixing, and placing operations;
determination of compliance with specifications; control for evaluating effectiveness of admixtures; and similar uses.
5.4 The individual who tests concrete cylinders for acceptance testing shall meet the concrete laboratory technician requirements
of Practice C1077, including an examination requiring performance demonstration that is evaluated by an independent examiner.
NOTE 1—Certification equivalent to the minimum guidelines for ACI Concrete Laboratory Technician, Level I or ACI Concrete Strength Testing
Technician will satisfy this requirement.
6. Apparatus
6.1 Testing Machine—The testing machine shall be of a type having sufficient capacity and capable of providing the rates of
loading prescribed in 8.5.
6.1.1 Verify the accuracy of the testing machine in accordance with Practices E4, except that the verified loading range shall be
as required in 6.4. Verification is required:
6.1.1.1 Within 13 months of the last calibration,
6.1.1.2 On original installation or immediately after relocation,
6.1.1.3 Immediately after making repairs or adjustments that affect the operation of the force applying system or the values
displayed on the load indicating system, except for zero adjustments that compensate for the mass of bearing blocks or specimen,
or both, or
6.1.1.4 Whenever there is reason to suspect the accuracy of the indicated loads.
6.1.2 Design—The design of the machine must include the following features:
6.1.2.1 The machine must be power operated and must apply the load continuously rather than intermittently, and without shock.
If it has only one loading rate (meeting the requirements of 8.5), it must be provided with a supplemental means for loading at
a rate suitable for verification. This supplemental means of loading may be power or hand operated.
6.1.2.2 The space provided for test specimens shall be large enough to accommodate, in a readable position, an elastic calibration
device which is of sufficient capacity to cover the potential loading range of the testing machine and which complies with the
requirements of Practice E74.
NOTE 2—The types of elastic calibration devices most generally available and most commonly used for this purpose are the circular proving ring or load
cell.
6.1.3 Accuracy—The accuracy of the testing machine shall be in accordance with the following provisions:
6.1.3.1 The percentage of error for the loads within the proposed range of use of the testing machine shall not exceed 61.0 % of
the indicated load.
6.1.3.2 The accuracy of the testing machine shall be verified by applying five test loads in four approximately equal increments
in ascending order. The difference between any two successive test loads shall not exceed one third of the difference between the
maximum and minimum test loads.
6.1.3.3 The test load as indicated by the testing machine and the applied load computed from the readings of the verification device
shall be recorded at each test point. Calculate the error, E, and the percentage of error, E , for each point from these data as follows:
p
E 5 A 2 B (1)
E 5 100 A 2 B /B
~ !
p
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where:
A = load, kN [lbf] indicated by the machine being verified, and
B = applied load, kN [lbf] as determined by the calibrating device.
6.1.3.4 The report on the verification of a testing machine shall state within what loading range it was found to conform to
specification requirements rather than reporting a blanket acceptance or rejection. In no case shall the loading range be stated as
including loads below the value which is 100 times the smallest change of load estimable on the load-indicating mechanism of
the testing machine or loads within that portion of the range below 10 % of the maximum range capacity.
6.1.3.5 In no case shall the loading range be stated as including loads outside the range of loads applied during the verification
test.
6.1.3.6 The indicated load of a testing machine shall not be corrected either by calculation or by the use of a calibration diagram
to obtain values within the required permissible variation.
6.2 Bearing Blocks—The upper and lower bearing blocks shall conform to the following requirements:
6.2.1 Bearing blocks shall be steel with hardened bearing faces (Note 3).
6.2.2 Bearing faces shall have dimensions at least 3 % greater than the nominal diameter of the specimen.
6.2.3 Except for the inscribed concentric circles described in 6.2.4.7, the bearing faces shall not depart from a plane by more than
0.02 mm [0.001 in.] along any 150 mm [6 in.] length for bearing blocks with a diameter of 150 mm [6 in.] or larger, or by more
than 0.02 mm [0.001 in.] in any direction of smaller bearing blocks. New bearing blocks shall be manufactured within one half
of this tolerance.
NOTE 3—It is desirable that the bearing faces of bearing blocks have a Rockwell hardness at least 55 HRC as determined by Test Methods E18.
NOTE 4—Square bearing faces are permissible for the bearing blocks.
6.2.4 Upper Bearing Block—The upper bearing block shall conform to the following requirements:
6.2.4.1 The upper bearing block shall be spherically seated and the center of the sphere shall coincide with the center of the bearing
face within 65 % of the radius of the sphere.
T ≥ R – r
r = radius of spherical portion of upper bearing block
R = nominal radius of specimen
T = thickness of upper bearing block extending beyond the sphere
FIG. 1 Schematic Sketch of Typical Upper Bearing Block
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6.2.4.2 The ball and the socket shall be designed so that the steel in the contact area does not permanently deform when loaded
to the capacity of the testing machine.
NOTE 5—The preferred contact area is in the form of a ring (described as preferred bearing area) as shown in Fig. 1.
6.2.4.3 Provision shall be made for holding the upper bearing block in the socket. The design shall be such that the bearing face
can be rotated and tilted at least 4° in any direction.
6.2.4.4 If the upper bearing block is a two-piece design composed of a spherical portion and a bearing plate, a mechanical means
shall be provided to ensure that the spherical portion is fixed and centered on the bearing plate.
6.2.4.5 The diameter of the sphere shall be at least 75 % of the nominal diameter of the specimen. If the diameter of the sphere
is smaller than the diameter of the specimen, the portion of the bearing face extending beyond the sphere shall have a thickness
not less than the difference between the radius of the sphere and radius of the specimen (see Fig. 1). The least dimension of the
bearing face shall be at least as great as the diameter of the sphere.
6.2.4.6 The dimensions of the bearing face of the upper bearing block shall not exceed the following values:
Nominal Diameter Maximum Diameter Maximum Dimensions
of Specimen, of Round Bearing of Square Bearing
mm [in.] Face, mm [in.] Face, mm [in.]
50 [2] 105 [4] 105 by 105 [4 by 4]
75 [3] 130 [5] 130 by 130 [5 by 5]
100 [4] 165 [6.5] 165 by 165 [6.5 by 6.5]
150 [6] 255 [10] 255 by 255 [10 by 10]
200 [8] 280 [11] 280 by 280 [11 by 11]
6.2.4.7 If the diameter of the bearing face of the upper bearing block exceeds the nominal diameter of the specimen by more than
13 mm [0.5 in.], concentric circles not more than 0.8 mm [0.03 in.] deep and not more than 1 mm [0.04 in.] wide shall be inscribed
on the face of upper bearing block to facilitate proper centering.
6.2.4.8 At least every six months, or as specified by the manufacturer of the testing machine, clean and lubricate the curved
surfaces of the socket and of the spherical portion of the upper bearing block. The lubricant shall be a petroleum-type oil such as
conventional motor oil or as specified by the manufacturer of the testing machine.
NOTE 6—To ensure uniform seating, the upper bearing block is designed to tilt freely as it comes into contact with the top of the specimen. After contact,
further rotation is undesirable. Friction between the socket and the spherical portion of the head provides restraint against further rotation during loading.
Pressure-type greases can reduce the desired friction and permit undesired rotation of the spherical head and should not be used unless recommended
by the manufacturer of the testing machine. Petroleum-type oil such as conventional motor oil has been shown to permit the necessary friction to develop.
6.2.5 Lower Bearing Block—The lower bearing block shall conform to the following requirements:
6.2.5.1 The lower bearing block shall be solid.
6.2.5.2 The top and bottom surfaces of the lower bearing block shall be parallel to each other.
6.2.5.3 The lower bearing block shall be at least 25 mm [1.0 in.] thick when new, and at least 22.5 mm [0.9 in.] thick after
resurfacing.
6.2.5.4 The lower bearing block shall be fully supported by the platen of the testing machine or by any spacers used.
6.2.5.5 If the testing machine is designed that the platen itself is readily maintained in the specified surface condition, a lower
bearing block is not required.
NOTE 7—The lower bearing block may be fastened to the platen of the testing machine.
NOTE 8—Inscribed concentric circles as described in 6.2.4.7 are optional on the lower bearing block.
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6.3 Spacers—If spacers are used, the spacers shall be placed under the lower bearing block and shall conform to the following
requirements:
6.3.1 Spacers shall be solid steel. One vertical opening located in the center of the spacer is permissible. The maximum diameter
of the vertical opening is 19 mm [0.75 in.].
6.3.2 The top and bottom surfaces of the spacer shall be parallel to each other.
6.3.3 Spacers shall be fully supported by the platen of the test machine.
6.3.4 Spacers shall fully support the lower bearing block and any spacers above.
6.3.5 Spacers shall not be in direct contact with the specimen or the retainers of unbonded caps.
6.4 Load Indication—The testing machine shall be equipped with either a dial or digital load indicator.
6.4.1 The verified loading range shall not include loads less than 100 times the smallest change of load that can be read.
6.4.2 A means shall be provided that will record, or indicate until reset, the maximum load to an accuracy within 1.0 % of the
load.
6.4.3 If the load is displayed on a dial, the graduated scale shall be readable to at least the nearest 0.1 % of the full scale load (Note
9). The dial shall be readable within 1.0 % of the indicated load at any given load level within the loading range. The dial pointer
shall be of sufficient length to reach the graduation marks. The width of the end of the pointer shall not exceed the clear distance
between the smallest graduations. The scale shall be provided with a labeled graduation line load corresponding to zero load. Each
dial shall be equipped with a zero adjustment located outside the dial case and accessible from the front of the machine while
observing the zero mark and dial pointer.
NOTE 9—Readability is considered to be 0.5 m
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