Studies of the Accelerated Curing of Concrete Test Specimens

摘要

Concrete is normally specified in terms of the 28-day strength but it would be of considerable advantage to be able to predict within a short time of its being mixed whether it is likely to reach the specified strength at 28 days. An accelerated curing method has been proposed and discussed by the Institution of Civil Engineers and is generally accepted but there are some doubts as to whether the rigid time limits specified would be operable under the variety of conditions that obtain on different construction sites. This test has therefore been studied in detail with a view to modifying the time-scale of the curing regime so that it is acceptable under all site conditions. Proposals are made for allowing the specimens to stand for 1 - 3 hours before commencing the accelerated curing cycle, and afterwards to cool in water for a period of 1 - 2 hours before test. The curing period is reduced to 20 hours in order to accommodate these pre-curing and post-curing periods within a cycle of nominally 24 hours. It is shown that for a wide range of aggregates and ordinary Portland cements the difference in concrete strengths caused by using the extremes of the time tolerances before and after accelerated curing is less than that obtained for the extremes of the time tolerances of the ICE test. (Author)