ASTM C1768/C1768M-12

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)

General Information

• Status: Historical
• Publication Date: 30-Nov-2012
• ICS: 91.100.30 - Concrete and concrete products
• Technical Committee: C09 - Concrete and Concrete Aggregates
• Drafting Committee: C09.61 - Testing for Strength

Relations

• Replaced By: ASTM C1768/C1768M-12(2017) - Standard Practice for Accelerated Curing of Concrete Cylinders
• Effective Date: 15-Mar-2017
• Referred By: ASTM C918/C918M-20 - Standard Test Method for Measuring Early-Age Compressive Strength and Projecting Later-Age Strength
• Effective Date: 01-Dec-2012
• Referred By: ASTM C1898-20 - Standard Test Methods for Determining the Chemical Resistance of Concrete Products to Acid Attack
• Effective Date: 01-Dec-2012
• Referred By: ASTM C1074-19e1 - Standard Practice for Estimating Concrete Strength by the Maturity Method
• Effective Date: 01-Dec-2012
• Referred By: ASTM C1904-22 - Standard Test Methods for Determination of the Effects of Biogenic Acidification on Concrete Antimicrobial Additives and/or Concrete Products
• Effective Date: 01-Dec-2012

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: C1768/C1768M − 12
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 C192/C192M Practice for Making and Curing Concrete Test
Specimens in the Laboratory
1.1 This practice covers two procedures for making and
C231/C231M Test Method forAir Content of Freshly Mixed
curing cylindrical specimens of concrete under conditions that
Concrete by the Pressure Method
increase the rate of hydration at early ages.The procedures are:
C470/C470M Specification for Molds for Forming Concrete
A—Warm Water Method and B—Autogenous Curing Method.
Test Cylinders Vertically
1.2 The values stated in either SI units or inch-pound units
C918/C918M Test Method for Measuring Early-Age Com-
are to be regarded separately as standard. The values stated in
pressive Strength and Projecting Later-Age Strength
each system may not be exact equivalents; therefore, each
C1064/C1064M Test Method for Temperature of Freshly
system shall be used independently of the other. Combining
Mixed Hydraulic-Cement Concrete
values from the two systems may result in non-conformance
C1231/C1231M Practice for Use of Unbonded Caps in
with the standard.
DeterminationofCompressiveStrengthofHardenedCon-
1.3 This standard does not purport to address all of the
crete Cylinders
safety concerns, if any, associated with its use. It is the
3. Terminology
responsibility of the user of this standard to establish appro-
3.1 Definitions:
priate safety and health practices and determine the applica-
3.1.1 For definitions of terms used in this practice, refer to
bility of regulatory limitations prior to use. (Warning—Fresh
Terminology C125.
hydraulic cementitious mixtures are caustic and may cause
chemical burns to skin and tissue upon prolonged exposure. )
4. Summary of Practice
2. Referenced Documents
4.1 Molded concrete cylindrical specimens are cured under
conditions that increase the early-age concrete temperature and
2.1 ASTM Standards:
the rate of hydration. This permits the specimens to develop a
C31/C31M Practice for Making and Curing Concrete Test
significant portion of their ultimate properties within a time
Specimens in the Field
period ranging from 24 to 49 h, depending upon the procedure
C39/C39M Test Method for Compressive Strength of Cylin-
used. In Procedure A, specimens are stored in a warm water
drical Concrete Specimens
bath for 24 h. In Procedure B, specimens are stored for 48 h in
C125 Terminology Relating to Concrete and Concrete Ag-
insulated curing containers in which the elevated curing
gregates
temperature is obtained from heat of hydration of the cement.
C143/C143M Test Method for Slump of Hydraulic-Cement
If specimens are to be used for estimating strength potential in
Concrete
accordance with Test Method C918/C918M, specimen tem-
C172/C172M Practice for Sampling Freshly Mixed Con-
perature is monitored during the accelerated curing period.
crete
C173/C173M Test Method forAir Content of Freshly Mixed 4.2 Table 1 summarizes important characteristics of these
Concrete by the Volumetric Method
curing procedures.
5. Significance and Use
This test method is under the jurisdiction of ASTM Committee C09 on
5.1 By increasing the concrete temperature, the rate of
Concrete and ConcreteAggregates and is the direct responsibility of Subcommittee
hydration increases and a larger portion of the later-age
C09.61 on Testing for Strength.
Current edition approved Dec. 1, 2012. Published January 2013. DOI: 10.1520/
properties of the concrete can be attained during the short
C1768_C1768M-12.
curing period compared with standard temperature curing as
See Section on Safety Precautions, Manual ofAggregate and Concrete Testing,
described in Practice C31/C31M and Practice C192/C192M.
Annual Book of ASTM Standards, Vol. 04.02.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
5.2 Specimens subjected to accelerated curing can be used
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
to estimate the later-age strength under standard-curing condi-
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. tions by using this practice in conjunction with Test Method
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1768/C1768M − 12
TABLE 1 Characteristics of Accelerated Curing Procedures
3°C [5°F]; and (3) returning to the specified water temperature
Accelerated within 15 min after immersion of specimens. A temperature
Duration of
Curing Age at
recording device, independent of the thermostat, is required to
Procedure Molds Accelerated
Temperature Testing
Curing
monitor the water temperature.
°C [°F]
A. Reusable or 35[95] 23.5h±30 24h±15
NOTE 2—Depending upon the design features of the tank, insulation or
Warm Water single-use min min
mechanical agitation, or both, might be necessary to meet the specified
temperature requirements. Electrical immersion heaters controlled by a
B. Single-use Initial 48h±15 49h±15
thermostat have been used successfully to meet the water temperature
Autogenous concrete min min
requirements. The size of the heating element(s) required will depend
Curing temperature
uponthesizeofthetankandthenumberandsizeofspecimenstobecured
augmented
by heat of at one time. A lid may be provided to reduce evaporation and heat loss.
hydration
6.3.1.3 The support for the specimens is designed to permit
circulation of water within the tank.
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
connected to a data logger or other device for a continuous
5.3 The user shall select the procedure to use on the basis of
record of the temperature history within the container. The
experience and local conditions. These procedures, in general,
maximum interval between temperature measurements is 30
will be practical if a field laboratory is available to house the
min.
curing containers and the testing equipment to measure com-
6.3.2.5 The container has a lid or other means to provide
pressive strength within the specified time limits.
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:
6.3.1.1 The tank is of any configuration suitable for the
8. Slump, Air Content, and Temperature
number of cylinders to be cured. Arrange the cylinders in a
configurationthatprovidesaclearanceofatleast50mm[2in.]
8.1 Slump—Measure and record the slump in accordance
between the surface of each cylinder and the wall of the tank, with Test Method C143/C143M of each sample of concrete
and at least 100 mm [4 in.] between adjacent cylinders.
from which specimens are made.
Maintain the water level at least 100 mm [4 in.] above the tops
8.2 Air Content—Measure and record the air content in
of the cylinders.
accordance with either Test Method C173/C173M or Test
Method C231/C231M. The concrete used in performing the air
NOTE 1—It may be convenient to have an overflow pipe for controlling
the water depth in the tank. A number of different tanks have been used
content test shall not be used in fabricating test specimens.
successfully. A schematic of a suitable curing tank is given in Appendix
8.3 Temperature—Measure and record the concrete tem-
X1.
perature in accordance with Test Method C1064/C1064M.
6.3.1.2 Equip the tank with environmental control ele-
ment(s)capableof: (1)maintainingthewatertemperatureat35
9. Procedure
63°C[95 65°F]atanypointinthewater;and (2)limitingthe
temperature drop, after immersion of specimens, to less than 9.1 Procedure A—Warm Water Method:
C1768/C1768M − 12
9.1.1 Prepa
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