Can accelerated tests for compressive strength be used as acceptance tests for concrete?
Such tests are not yet in general use. Nevertheless in 1971 the American Society for Testing and Materials adopted as a tentative standard ASTM C 684-71T, which provides a 24-hour test method for concrete compressive strength. The standard warns: "Because strength requirements in existing specifications and codes are not based upon accelerated curing, use of results from this method in the prediction of specification compliance of strengths at later ages must be applied with great caution." In an editorial in the May 1973 issue of the ACI Journal, Robert Philleo, ACI president, comments that he is as yet unaware of any ACI move "to simplify construction administration by making this test the acceptance test for concrete." He does believe that steps should be taken to adopt such accelerated methods, however, pointing out a case in which a 15-story building was topped out in eight days but in which the concrete supplier had to wait an additional three weeks for the 28-day strength results before he knew whether he would be paid and the structural engineer had to wait the same time to learn whether the structure conformed to his design.