ASTM C918/C918M-07

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

SIGNIFICANCE AND USE
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.5 The early-age test results provide information on the variability of the concrete production process for use in process control.
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.
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.
This test method is not intended for estimating the in-place strength of concrete. Practice C 1074 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-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.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 14-Jul-2007
• 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 C918-02 - Standard Test Method for Measuring Early-Age Compressive Strength and Projecting Later-Age Strength
• Effective Date: 15-Jul-2007
• Replaced By: ASTM C918/C918M-13 - Standard Test Method for Measuring Early-Age Compressive Strength and Projecting Later-Age Strength
• Effective Date: 01-Dec-2013
• Referred By: ASTM C1768/C1768M-12(2017) - Standard Practice for Accelerated Curing of Concrete Cylinders
• Effective Date: 15-Jul-2007
• Referred By: ASTM C1074-19e1 - Standard Practice for Estimating Concrete Strength by the Maturity Method
• Effective Date: 15-Jul-2007

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: C918/C918M − 07
StandardTest 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* C192/C192M Practice for Making and Curing Concrete Test
Specimens in the Laboratory
1.1 This test method covers a procedure for making and
C470/C470M Specification for Molds for Forming Concrete
curing concrete specimens and for testing them at an early age.
Test Cylinders Vertically
The specimens are stored under standard-curing conditions and
C617 Practice for Capping Cylindrical Concrete Specimens
themeasuredtemperaturehistoryisusedtocomputeamaturity
C670 Practice for Preparing Precision and Bias Statements
index that is related to strength gain.
for Test Methods for Construction Materials
1.2 This test method also covers a procedure for using the
C1074 Practice for Estimating Concrete Strength by the
results of early-age compressive-strength tests to project the
Maturity Method
potential strength of concrete at later ages.
C1231/C1231M Practice for Use of Unbonded Caps in
1.3 The values stated in either SI units or inch-pound units
DeterminationofCompressiveStrengthofHardenedCon-
are to be regarded separately as standard. The values stated in
crete Cylinders
each system may not be exact equivalents; therefore, each
system shall be used independently of the other. Combining
3. Terminology
values from the two systems may result in non-conformance
with the standard. 3.1 Definitions:
3.1.1 Refer to Practice C1074 for the definitions of the
1.4 The text of this standard references notes and footnotes
following terms: datum temperature, equivalent age, maturity,
which provide explanatory material. These notes and footnotes
(excluding those in tables and figures) shall not be considered maturityfunction,maturityindex,andtemperature–timefactor.
as requirements of the standard. 3.2 Definitions of Terms Specific to This Standard:
1.5 This standard does not purport to address all of the 3.2.1 potential strength, n—the strength of a test specimen
safety concerns, if any, associated with its use. It is the
that would be obtained at a specified age under standard curing
responsibility of the user of this standard to establish appro-
conditions.
priate safety and health practices and determine the applica-
3.2.2 prediction equation, n—the equation representing the
bility of regulatory limitations prior to use.
straight-line relationship between compressive strength and the
logarithm of the maturity index.
2. Referenced Documents
2 3.2.2.1 Discussion—The prediction equation is used to proj-
2.1 ASTM Standards:
ect the strength of a test specimen based upon its measured
C31/C31M Practice for Making and Curing Concrete Test
early-age strength. The general form of the prediction equation
Specimens in the Field
used in this test method is:
C39/C39M Test Method for Compressive Strength of Cylin-
drical Concrete Specimens
S 5 S 1b log M 2 log m (1)
~ !
M m
where:
1
S = projected strength at maturity index M,
This test method is under the jurisdiction of ASTM Committee C09 on
M
Concrete and Concrete Aggregatesand is the direct responsibility of Subcommittee
S = measured compressive strength at maturity index m,
m
C09.61 on Testing for Strength.
b = slope of the line,
Current edition approved July 15, 2007. Published August 2007. Originally
M = maturity index under standard curing conditions, and
approved in 1980. Last previous edition approved in 2002 as C918 – 02. DOI:
m = maturity index of the specimen tested at early age.
10.1520/C0918_C0918M-07.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
The prediction equation is developed by performing
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
compressive strength tests at various ages, computing the
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. corresponding maturity indices at the test ages, and plotting
*A Summary of Changes section appears at the end of this standard
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C918/C918M − 07
thecompressivestrengthasafunctionofthelogarithmofthe 6. Apparatus
maturity index. A best-fit line is drawn through the data and
6.1 Equipment and Small Tools, for fabricating specimens
the slope of this line is used in the prediction equation.
and measuring the character
...