ACCELERATED METHODS OF ESTIMATING THE STRENGTH OF CONCRETE

This paper gives the results of an experimental investigation to develop equations for estimating the portntial strength of concrete by using the accelerated-curing methods recommended by the American Society for Testing and Materials. Cylinders made from 21 different batches of concrete were tested. Ranges of variables included in this investigation were types of cements (1,2, and K); types of molds (steel, plastic, and cardboard); water-cement ratios (by weight), 0.41 to 0.72; aggregate-cement ratios (by weight), 2.5 to 4.1; maximum size of coarse aggregate, 1 in. (25.4 mm); and the 28-day compressive strength, 3,400 to 6,800 psi (23 500 to 46 900 KPa). An equation and correlation curves are presented for the locally used materials and mixes relating the strength of types 1,2, and K cement concretes obtained in the accelerated-curing methods and the 28-day strength obtained with standard-curing conditions. Based on the results from this investigation and those of other investigators from various parts of the world, and equation applicable universally with reasonable accuracy is presented for estimating the potential strength of concrete by using accelerated-curing methods. Equations based on maturity concept are also presented to predict the strength of concrete when the water-cement ratio, duration, and temperature of curing are known. The results of this investigation are compared and analyzed in relation to published works.