Shrinkage cracking properties of slag concretes with one-day curing

Abstract

The current paper presents the results of a restrained shrinkage test that captures the shrinkage, tensile creep and tensile stress plotted against strain behaviour of early-age concretes. Four types of concrete mixes were studied: concretes made with ordinary Portland cement (OPC) and slag-blended cements with 35%, 50% and 65% replacement of OPC. Two identical specimens of each mix were tested: one subjected to fully restrained conditions and the other allowed to shrink freely, both under the drying conditions of 23°C and 50% relative humidity at the age of 24 h. Indirect tensile tests were also performed in the same concretes to monitor the tensile strength development. With increasing slag contents, the tensile strength decreased, which is detrimental to crack resistance. However, with increasing slag contents, the elastic modulus also decreased, which is beneficial to crack resistance. The slag content levels did not significantly influence the shrinkage and creep characteristics. Increasing slag levels did not significantly alter the time to cracking behaviours owing to the compensating effects of decreasing tensile strength and elastic modulus.