ASTM C918/C918M-20

Standard Test Method for Measuring Early-Age Compressive Strength and Projecting Later-Age Strength

SIGNIFICANCE AND USE
5.1 This test method provides a procedure to estimate the potential strength of a particular test specimen based upon its measured strength at an age as early as 24 h.4 The early-age test results provide information on the variability of the concrete production process for use in process control.  
5.2 The relationship between early-age strength of test specimens and strength achieved at some later age under standard curing depends upon the materials comprising the concrete. In this test method, it is assumed that there is a linear relationship between strength and the logarithm of the maturity index. Experience has shown that this is an acceptable approximation for test ages between 24 h and 28 days under standard curing conditions. The user of this test method shall verify that the test data used to develop the prediction equation are represented correctly by the linear relationship. If the underlying relationship between strength and the logarithm of the maturity index cannot be approximated by a straight line, the principle of this test method is applicable provided an appropriate equation is used to represent the non-linear relationship.  
5.3 Strength projections are limited to concretes using the same materials and proportions as the concrete used to establish the prediction equation.
Note 1: Confidence intervals developed in accordance with 10.2 are helpful in evaluating projected strengths.  
5.4 This test method is not intended for estimating the in-place strength of concrete. Practice C1074 provides procedures for using the measured in-place maturity index to estimate in-place strength.
SCOPE
1.1 This test method covers a procedure for making and curing concrete specimens and for testing them at an early age. The specimens are stored under standard or accelerated curing conditions and the measured temperature history is used to compute a maturity index that is related to strength gain.  
1.2 This test method also covers a procedure for using the results of early-age compressive-strength tests to project the potential strength of concrete at later ages.  
1.3 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.  
1.4 The text of this standard references notes and footnotes which provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of 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 skin and tissue upon prolonged exposure.)2  
1.6 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-2020
• ICS: 91.100.30 - Concrete and concrete products
• Technical Committee: C09 - Concrete and Concrete Aggregates
• Drafting Committee: C09.61 - Testing for Strength

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: C918/C918M − 20
Standard Test Method for
Measuring Early-Age Compressive Strength and Projecting
1
Later-Age Strength
This standard is issued under the fixed designation C918/C918M; 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.
1. Scope* 2. Referenced Documents
3
1.1 This test method covers a procedure for making and 2.1 ASTM Standards:
curing concrete specimens and for testing them at an early age. C31/C31M Practice for Making and Curing Concrete Test
The specimens are stored under standard or accelerated curing Specimens in the Field
conditions and the measured temperature history is used to C39/C39M Test Method for Compressive Strength of Cylin-
compute a maturity index that is related to strength gain. drical Concrete Specimens
C125 Terminology Relating to Concrete and Concrete Ag-
1.2 This test method also covers a procedure for using the
gregates
results of early-age compressive-strength tests to project the
C192/C192M Practice for Making and Curing Concrete Test
potential strength of concrete at later ages.
Specimens in the Laboratory
1.3 The values stated in either SI units or inch-pound units
C470/C470M Specification for Molds for Forming Concrete
are to be regarded separately as standard. The values stated in
Test Cylinders Vertically
each system may not be exact equivalents; therefore, each
C617/C617M Practice for Capping Cylindrical Concrete
system shall be used independently of the other. Combining
Specimens
values from the two systems may result in non-conformance
C670 Practice for Preparing Precision and Bias Statements
with the standard.
for Test Methods for Construction Materials
1.4 The text of this standard references notes and footnotes C1074 Practice for Estimating Concrete Strength by the
Maturity Method
which provide explanatory material. These notes and footnotes
(excluding those in tables and figures) shall not be considered C1231/C1231M Practice for Use of Unbonded Caps in
Determination of Compressive Strength of Hardened Cy-
as requirements of the standard.
lindrical Concrete Specimens
1.5 This standard does not purport to address all of the
C1768/C1768M Practice forAccelerated Curing of Concrete
safety concerns, if any, associated with its use. It is the
Cylinders
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
3. Terminology
mine the applicability of regulatory limitations prior to use.
3.1 Definitions:
(Warning—Fresh hydraulic cementitious mixtures are caustic
3.1.1 For definitions of terms used in this test method, refer
and may cause chemical burns to skin and tissue upon
2
to Terminology C125.
prolonged exposure.)
3.2 Definitions of Terms Specific to This Standard:
1.6 This international standard was developed in accor-
3.2.1 potential strength, n—the strength of a test specimen
dance with internationally recognized principles on standard-
that would be obtained at a specified age under standard curing
ization established in the Decision on Principles for the
conditions.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
3.2.2 prediction equation, n—the equation representing the
Barriers to Trade (TBT) Committee.
straight-line relationship between compressive strength and the
logarithm of the maturity index.
3.2.2.1 Discussion—The prediction equation is used to proj-
1
This test method is under the jurisdiction of ASTM Committee C09 on
ect the strength of a test specimen based upon its measured
Concrete and ConcreteAggregates and is the direct responsibility of Subcommittee
C09.61 on Testing for Strength.
Current edition approved April 1, 2020. Published May 2020. Originally
3
approved in 1980. Last previous edition approved in 2013 as C918 – 13. DOI: For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10.1520/C0918_C0918M-20. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
2
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. 04.0.2. 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
1

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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: C918/C918M − 13 C918/C918M − 20
Standard Test Method for
Measuring Early-Age Compressive Strength and Projecting
1
Later-Age Strength
This standard is issued under the fixed designation C918/C918M; 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.
1. Scope*
1.1 This test method covers a procedure for making and curing concrete specimens and for testing them at an early age. The
specimens are stored under standard or accelerated curing conditions and the measured temperature history is used to compute a
maturity index that is related to strength gain.
1.2 This test method also covers a procedure for using the results of early-age compressive-strength tests to project the potential
strength of concrete at later ages.
1.3 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.
1.4 The text of this standard references notes and footnotes which provide explanatory material. These notes and footnotes
(excluding those in tables and figures) shall not be considered as requirements of 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use. (Warning—Fresh hydraulic cementitious mixtures are caustic and may cause
2
chemical burns to skin and tissue upon prolonged exposure.)
1.6 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
3
2.1 ASTM Standards:
C31/C31M Practice for Making and Curing Concrete Test Specimens in the Field
C39/C39M Test Method for Compressive Strength of Cylindrical Concrete Specimens
C125 Terminology Relating to Concrete and Concrete Aggregates
C192/C192M Practice for Making and Curing Concrete Test Specimens in the Laboratory
C470/C470M Specification for Molds for Forming Concrete Test Cylinders Vertically
C617/C617M Practice for Capping Cylindrical Concrete Specimens
C670 Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials
C1074 Practice for Estimating Concrete Strength by the Maturity Method
C1231/C1231M Practice for Use of Unbonded Caps in Determination of Compressive Strength of Hardened Cylindrical
Concrete Specimens
C1768/C1768M Practice for Accelerated Curing of Concrete Cylinders
3. Terminology
3.1 Definitions:
1
This test method is under the jurisdiction of ASTM Committee C09 on Concrete and Concrete Aggregates and is the direct responsibility of Subcommittee C09.61 on
Testing for Strength.
Current edition approved Dec. 1, 2013April 1, 2020. Published January 2014May 2020. Originally approved in 1980. Last previous edition approved in 20072013 as
C918 – 07.C918 – 13. DOI: 10.1520/C0918_C0918M-13.10.1520/C0918_C0918M-20.
2
Section on Safety Precautions, Manual of Aggregate and Concrete Testing, Annual Book of ASTM Standards, Vol. 04.0.2.
3
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
1

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C918/C918M − 20
3.1.1 Refer to Practice For C1074 for the definitions of the following terms:terms used in datum temperature,this test method,
equivalent age,refer to maturity,Terminology C125maturity function,. maturity index, and temperature–time factor.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 potential strength, n—the
...