As an acceptance test the standard 28-day compressive strength test (ASTM C 39) is wanting. It gives its verdict long after that verdict is first needed and at a time when frequently the designer, contractor and owner might almost prefer not to know the result. One engineer has pointed out the absurdity and inconvenience of depending on this test for acceptance, citing among several examples a 15-story hotel in which all concrete floors were cast before the first 28-day cylinder test result was available. The structure was almost complete before any of the concrete had been accepted. A new test has been developed that gives strength results 5 hours after the test cylinders are made. Such strength test data also must be adjusted to provide an estimate of standard ASTM C 39 strength results. Even 5 hours may be longer than ideally one might want to wait. Nevertheless, it is early enough to make it much easier to solve the problem of any strengths that are below specification. The developer of the test lists the following advantages to the contractor: If the 5-hour test indicates that the concrete is sound, the contractor can have confidence in stripping his forms on schedule; if the test shows the concrete is of low quality he can promptly take any remedial action needed, including, if necessary, removal of the concrete while such work can still be done fairly easily; and, if the concrete is well above the required strength the concrete supplier can be asked to modify the mix to reduce the cost. Essentially the method involves making three 3- by 6-inch cylinders in special heavy-duty molds, curing the concrete under pressure at high temperatures for 3 hours and breaking the cylinders after they have cooled for 2 hours. The test equipment is small enough to be carried in the trunk of a car and can be used wherever there is access to a 110-volt electric outlet. It is said to take about half an hour to set up for testing.