ASTM C684-99(2003) (R1999)

1.1 This test method covers four procedures for making, curing, and testing specimens of concrete stored under conditions intended to accelerate the development of strength. The four procedures are: Procedure A-Warm Water Method, Procedure B-Boiling Water Method, Procedure C-Autogenous Curing Method, and Procedure D-High Temperature and Pressure Method.

1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses are provided for information purposes only.

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. See Section 9 and Note 9 and 14 for specific warnings and precautions.

The accelerated curing procedures provide, at the earliest practical time, an indication of the potential strength of a specific concrete mixture. These procedures also provide information on the variability of the production process for use in quality control.

The accelerated early strength obtained from any of the procedures in this test method can be used to evaluate concrete strengths in the same way conventional 28-day strengths have been used in the past, with suitable changes in the expected strength values. Since the practice of using strength values obtained from standard-cured cylinders at 28 days is long established and widespread, the results of accelerated strength tests are often used to estimate the later-age strength under standard curing. Such estimates should be limited to concretes using the same materials and mixture proportions as those used for establishing the correlation. Appendix X2 provides a procedure to estimate the 90 % confidence interval of the average later-age strength based on accelerated strength test results.

Correlation between accelerated strength and strength achieved at some later age by using conventional curing methods depends upon the materials comprising the concrete, the mixture proportions, and the specific accelerated test procedure.

The user shall choose which procedure to use on the basis of experience and local conditions. These procedures, in general, will be practical when a field laboratory is available to house the curing containers and the testing equipment to measure compressive strength within the specified time limits.