Influence of different curing conditions on the physical and mechanical properties of concretes with admixtures of silica fume and blast furnace slag

Adequate curing is essential for the proper strength development, imperviousness and durability of concrete and concrete structures. In practice, structural concrete is seldom moist-cured for more than 7 days. Experimental studies are applied in determining the influence of a mineral admixture on the microstructure, capillary and porosity of concrete. The strength development and durability of concretes with silica fume (SF) and blast furnace slag (BFS) are reported to be critically dependent on the extent of curing and curing conditions. To improve the physical and mechanical properties of concrete, SF and BFS were used at different ratio instead of normal portland cement (PC). The dry unit weight, the compressive strength, the ultrasonic pulse velocity (UPV), capillarity coefficient and appearing porosity (AP) of the specimens were determined. The specimens were cured-in different curing regimes for periods varying from 28, 75, 150, to 400 days before exposure to the experiments. Finally, it was observed that the specimens with SF%10 + BFS%20 and 0.35 water-binder ratios had the highest compressive strength and UPV, the lowest capillarity coefficient and the appearing porosity. As a result, it can be concluded that the mineral admixtures improved the compressive strength, UPV, capillarity coefficient and appearing porosity. (C) 2003 Elsevier Science B.V. All rights reserved.