Active Standard ASTM C1768 / C1768M | Developed by Subcommittee: C09.61
Book of Standards Volume: 04.02
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.
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)
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
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
C143/C143M Test Method for Slump of Hydraulic-Cement Concrete
C172/C172M Practice for Sampling Freshly Mixed Concrete
C173/C173M Test Method for Air Content of Freshly Mixed Concrete by the Volumetric Method
C192/C192M Practice for Making and Curing Concrete Test Specimens in the Laboratory
C231/C231M Test Method for Air Content of Freshly Mixed Concrete by the Pressure Method
C470/C470M Specification for Molds for Forming Concrete Test Cylinders Vertically
C918/C918M Test Method for Measuring Early-Age Compressive Strength and Projecting Later-Age Strength
C1064/C1064M Test Method for Temperature of Freshly Mixed Hydraulic-Cement Concrete
C1231/C1231M Practice for Use of Unbonded Caps in Determination of Compressive Strength of Hardened Concrete Cylinders
ICS Number Code 91.100.30 (Concrete and concrete products)