ASTM C1768/C1768M-12(2017)

Standard Practice for Accelerated Curing of Concrete Cylinders

SIGNIFICANCE AND USE
5.1 By increasing the concrete temperature, the rate of hydration increases and a larger portion of the later-age properties of the concrete can be attained during the short curing period compared with standard temperature curing as described in Practice C31/C31M and Practice C192/C192M.  
5.2 Specimens subjected to accelerated curing can be used to estimate the later-age strength under standard-curing conditions by using this practice in conjunction with Test Method C918/C918M. The temperature history of the test specimens is recorded and the maturity index at the time of testing is calculated. Based on the measured maturity index and the early-age strength test results, the later age strength (such as at 28 days) under standard curing can be estimated from a previously established strength-maturity relationship for that concrete mixture. Thus accelerated curing procedures can provide, at the earliest practical time, an indication of the potential strength of the concrete sample. These early-age strength tests also provide information on the variability of the production process for use in quality control, so that necessary adjustments in mixture proportions can be made in a timely manner.  
5.3 The user shall select the procedure to use on the basis of experience and local conditions. These procedures, in general, will be practical if a field laboratory is available to house the curing containers and the testing equipment to measure compressive strength within the specified time limits.
SCOPE
1.1 This practice covers two procedures for making and curing cylindrical specimens of concrete under conditions that increase the rate of hydration at early ages. The procedures are: A—Warm Water Method and B—Autogenous Curing Method.  
1.2 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.  
1.3 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 and health 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)  
1.4 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: 14-Mar-2017
• 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 C1768/C1768M-12 - Standard Practice for Accelerated Curing of Concrete Cylinders
• Effective Date: 15-Mar-2017
• Refers: ASTM C31/C31M-24a - Standard Practice for Making and Curing Concrete Test Specimens in the Field
• Effective Date: 01-Apr-2024
• Refers: ASTM C173/C173M-24 - Standard Test Method for Air Content of Freshly Mixed Concrete by the Volumetric Method
• 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 C231/C231M-24 - Standard Test Method for Air Content of Freshly Mixed Concrete by the Pressure Method
• 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 C39/C39M-23 - Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens
• Effective Date: 01-Dec-2023
• Refers: ASTM C1231/C1231M-23 - Standard Practice for Use of Unbonded Caps in Determination of Compressive Strength of Hardened Cylindrical Concrete Specimens
• Effective Date: 01-Oct-2023
• Refers: ASTM C173/C173M-23 - Standard Test Method for Air Content of Freshly Mixed Concrete by the Volumetric Method
• Effective Date: 01-Sep-2023
• Refers: ASTM C125-19a - Standard Terminology Relating to Concrete and Concrete Aggregates
• Effective Date: 15-Dec-2019
• Refers: ASTM C125-19 - Standard Terminology Relating to Concrete and Concrete Aggregates
• Effective Date: 01-Jan-2019
• Refers: ASTM C125-18b - Standard Terminology Relating to Concrete and Concrete Aggregates
• Effective Date: 01-Oct-2018
• Refers: ASTM C125-18a - Standard Terminology Relating to Concrete and Concrete Aggregates
• Effective Date: 01-Jul-2018
• Refers: ASTM C125-18 - Standard Terminology Relating to Concrete and Concrete Aggregates
• Effective Date: 01-Jan-2018
• Refers: ASTM C31/C31M-18 - Standard Practice for Making and Curing Concrete Test Specimens in the Field
• Effective Date: 01-Jan-2018

Overview

ASTM C1768/C1768M-12(2017), “Standard Practice for Accelerated Curing of Concrete Cylinders,” establishes guidelines for preparing, curing, and testing cylindrical specimens of concrete under elevated temperature conditions to speed up hydration. The standard, developed by ASTM International, permits the estimation of later-age concrete properties in a reduced timeframe compared to traditional curing approaches. Two primary procedures are defined-Warm Water Method (A) and Autogenous Curing Method (B)-both designed to accelerate the development of concrete compressive strength.

This document is essential for construction and quality control professionals involved in concrete testing, particularly when rapid assessment of concrete performance is needed for time-sensitive projects.

Key Topics

• Accelerated Curing Methods
  • Warm Water Method (Procedure A): Uses a controlled water bath to elevate concrete temperature for a set period, increasing hydration rate.
  • Autogenous Curing Method (Procedure B): Relies on the heat of hydration within an insulated container, mimicking the temperature rise in larger concrete elements.
• Testing and Estimation
  • Accelerated curing enables estimate of 28-day or later-age strength of concrete based on early-age test results.
  • Strength prediction uses maturity index calculations and a previously established strength-maturity relationship specific to the mix.
• Equipment and Instrumentation
  • Requirements for curing tanks, molds, insulation, temperature control, and data logging are specified to ensure reliable results.
• Quality Control Applications
  • Early-age strength test results provide valuable information on both the potential strength and variability of the concrete mix, supporting timely adjustments in production.

Applications

ASTM C1768/C1768M-12(2017) is widely applied in the following areas:

• Construction Project Quality Control: Provides quick feedback on concrete strength, allowing construction to proceed or adjustments to be made shortly after placement.
• Precast Concrete Plants: Enables early release of forms and increased production efficiency by predicting final product strength based on early results.
• Research and Development: Serves as a reliable practice for laboratories investigating new concrete mixtures and additives needing rapid strength assessment.
• Field Testing: Especially valuable when standard curing conditions are impractical due to project deadlines or remote locations.
• Compliance Verification: Used as part of the acceptance criteria for concrete supplied to public works, commercial buildings, and infrastructure projects.

Related Standards

Several ASTM standards are referenced to ensure comprehensive testing and specimen preparation:

• ASTM C31/C31M - Practice for Making and Curing Concrete Test Specimens in the Field
• ASTM C39/C39M - Test Method for Compressive Strength of Cylindrical Concrete Specimens
• ASTM C192/C192M - Practice for Making and Curing Concrete Test Specimens in the Laboratory
• ASTM C918/C918M - Test Method for Measuring Early-Age Compressive Strength and Projecting Later-Age Strength
• ASTM C470/C470M - Specification for Molds for Forming Concrete Test Cylinders Vertically

By integrating ASTM C1768/C1768M with these standards, users can ensure consistency, reliability, and compliance during concrete testing and evaluation. This accelerates decision-making processes in construction and enhances overall quality assurance protocols.

Keywords: accelerated curing, compressive strength, concrete cylinders, early-age strength, warm water method, autogenous curing method, ASTM C1768/C1768M, concrete testing, quality control.

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: C1768/C1768M − 12 (Reapproved 2017)
Standard Practice for
Accelerated Curing of Concrete Cylinders
This standard is issued under the fixed designation C1768/C1768M; 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 C125 Terminology Relating to Concrete and Concrete Ag-
gregates
1.1 This practice covers two procedures for making and
C143/C143M Test Method for Slump of Hydraulic-Cement
curing cylindrical specimens of concrete under conditions that
Concrete
increase the rate of hydration at early ages.The procedures are:
C172/C172M Practice for Sampling Freshly Mixed Con-
A—Warm Water Method and B—Autogenous Curing Method.
crete
1.2 The values stated in either SI units or inch-pound units
C173/C173M Test Method forAir Content of Freshly Mixed
are to be regarded separately as standard. The values stated in
Concrete by the Volumetric Method
each system may not be exact equivalents; therefore, each
C192/C192M Practice for Making and Curing Concrete Test
system shall be used independently of the other. Combining
Specimens in the Laboratory
values from the two systems may result in non-conformance
C231/C231M Test Method forAir Content of Freshly Mixed
with the standard.
Concrete by the Pressure Method
1.3 This standard does not purport to address all of the
C470/C470M Specification for Molds for Forming Concrete
safety concerns, if any, associated with its use. It is the
Test Cylinders Vertically
responsibility of the user of this standard to establish appro-
C918/C918M Test Method for Measuring Early-Age Com-
priate safety and health practices and determine the applica-
pressive Strength and Projecting Later-Age Strength
bility of regulatory limitations prior to use. (Warning—Fresh
C1064/C1064M Test Method for Temperature of Freshly
hydraulic cementitious mixtures are caustic and may cause
Mixed Hydraulic-Cement Concrete
chemical burns to skin and tissue upon prolonged exposure. )
C1231/C1231M Practice for Use of Unbonded Caps in
1.4 This international standard was developed in accor-
Determination of Compressive Strength of Hardened Cy-
dance with internationally recognized principles on standard-
lindrical Concrete Specimens
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
3. Terminology
mendations issued by the World Trade Organization Technical
3.1 Definitions:
Barriers to Trade (TBT) Committee.
3.1.1 For definitions of terms used in this practice, refer to
2. Referenced Documents
Terminology C125.
2.1 ASTM Standards:
4. Summary of Practice
C31/C31M Practice for Making and Curing Concrete Test
Specimens in the Field
4.1 Molded concrete cylindrical specimens are cured under
C39/C39M Test Method for Compressive Strength of Cylin-
conditions that increase the early-age concrete temperature and
drical Concrete Specimens
the rate of hydration. This permits the specimens to develop a
significant portion of their ultimate properties within a time
period ranging from 24 to 49 h, depending upon the procedure
This test method is under the jurisdiction of ASTM Committee C09 on
used. In Procedure A, specimens are stored in a warm water
Concrete and ConcreteAggregates and is the direct responsibility of Subcommittee
bath for 24 h. In Procedure B, specimens are stored for 48 h in
C09.61 on Testing for Strength.
insulated curing containers in which the elevated curing
Current edition approved March 15, 2017. Published May 2017. Originally
temperature is obtained from heat of hydration of the cement.
approved in 2012. Last previous edition approved in 2012 as C1768/C1768M–12.
DOI: 10.1520/C1768_C1768M-12R17.
If specimens are to be used for estimating strength potential in
See Section on Safety Precautions, Manual ofAggregate and Concrete Testing,
accordance with Test Method C918/C918M, specimen tem-
Annual Book of ASTM Standards, Vol. 04.02.
3 perature is monitored during the accelerated curing period.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
4.2 Table 1 summarizes important characteristics of these
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. curing procedures.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1768/C1768M − 12 (2017)
TABLE 1 Characteristics of Accelerated Curing Procedures
and at least 100 mm [4 in.] between adjacent cylinders.
Accelerated Maintain the water level at least 100 mm [4 in.] above the tops
Duration of
Curing Age at
of the cylinders.
Procedure Molds Accelerated
Temperature Testing
Curing
°C [°F]
NOTE 1—It may be convenient to have an overflow pipe for controlling
A. Reusable or 35[95] 23.5h±30 24h±15 the water depth in the tank. A number of different tanks have been used
Warm Water single-use min min
successfully. A schematic of a suitable curing tank is given in Appendix
X1.
B. Single-use Initial 48h±15 49h±15
Autogenous concrete min min 6.3.1.2 Equip the tank with environmental control ele-
Curing temperature
ment(s)capableof: (1)maintainingthewatertemperatureat35
augmented
63°C[95 65°F]atanypointinthewater;and(2)limitingthe
by heat of
hydration temperature drop, after immersion of specimens, to less than
3°C [5°F]; and (3) returning to the specified water temperature
within 15 min after immersion of specimens. A temperature
recording device, independent of the thermostat, is required to
monitor the water temperature.
5. Significance and Use
NOTE 2—Depending upon the design features of the tank, insulation or
5.1 By increasing the concrete temperature, the rate of
mechanical agitation, or both, might be necessary to meet the specified
hydration increases and a larger portion of the later-age
temperature requirements. Electrical immersion heaters controlled by a
properties of the concrete can be attained during the short thermostat have been used successfully to meet the water temperature
requirements. The size of the heating element(s) required will depend
curing period compared with standard temperature curing as
uponthesizeofthetankandthenumberandsizeofspecimenstobecured
described in Practice C31/C31M and Practice C192/C192M.
at one time. A lid may be provided to reduce evaporation and heat loss.
5.2 Specimens subjected to accelerated curing can be used
6.3.1.3 The support for the specimens is designed to permit
to estimate the later-age strength under standard-curing condi-
circulation of water within the tank.
tions by using this practice in conjunction with Test Method
6.3.2 Curing Container for Procedure B-Autogenous Cur-
C918/C918M. The temperature history of the test specimens is
ing Method:
recorded and the maturity index at the time of testing is
6.3.2.1 The container consists of thermal insulation that
calculated. Based on the measured maturity index and the
surrounds closely the concrete specimen or specimens. Any
early-age strength test results, the later age strength (such as at
configurationisacceptableprovidedthecuringcontainermeets
28 days) under standard curing can be estimated from a
the heat retention and other requirements of Annex A1.
previously established strength-maturity relationship for that
6.3.2.2 The container is capable of holding one or more
concrete mixture. Thus accelerated curing procedures can
specimens.
provide, at the earliest practical time, an indication of the
6.3.2.3 The container is capable of being opened to permit
potential strength of the concrete sample. These early-age
insertion and withdrawal of the specimen(s) and has an outer
strength tests also provide information on the variability of the
casingandinnerlinertoprotecttheinsulationfrommechanical
production process for use in quality control, so that necessary
damage.
adjustments in mixture proportions can be made in a timely
6.3.2.4 The container has a temperature sensor that is not
manner.
insulatedfromthemoldedspecimen.Thetemperaturesensoris
5.3 The user shall select the procedure to use on the basis of connected to a data logger or other device for a continuous
experience and local conditions. These procedures, in general, record of the temperature history within the container. The
will be practical if a field laboratory is available to house the maximum interval between temperature measurements is 30
curing containers and the testing equipment to measure com- min.
pressive strength within the specified time limits. 6.3.2.5 The container has a lid or other means to provide
secure closure during the specified curing period. The lid
6. Apparatus includes a heat seal that satisfies the requirements of Annex
A1.
6.1 Small Tools and Equipment—For fabricating specimens
shallconformtoPracticeC31/C31MorPracticeC192/C192M,
NOTE 3—Schematics of suitable containers are included in Appendix
whichever is applicable. X1.
6.2 Cylinder Molds—Shall conform to Specification C470/
7. Sampling
C470M. Paper molds are not permitted. Procedure B requires
7.1 Sample the freshly mixed concrete in accordance with
single-use molds.
Practice C172/C172M unless another procedure is required by
6.3 Curing Apparatus:
the purchaser of the testing services. If applicable, record the
6.3.1 Accelerated Curing Tank for Procedure A-Warm Wa-
location where the sampled batch is placed in the structure.
ter Method:
8. Slump, Air Content, and Temperature
6.3.1.1 The tank is of any configuration suitable for the
number of cylinders to be cured. Arrange the cylinders in a 8.1 Slump—Measure and record the slump in accordance
configurationthatprovidesaclearanceofatleast50mm[2in.] with Test Method C143/C143M of each sample of concrete
between the surface of each cylinder and the wall of the tank, from which specimens are made.
C1768/C1768M − 12 (2017)
8.2 Air Content—Measure and record the air content in 9.2.1.2 If the specimens are to be teste
...