THE EFFECT OF ALTERNATE WETTING AND DRYING ON THE PROPERTIES OF PORTLAND BLAST-FURNACE CEMENT CONCRETES

Abstract

Experiments were carried out to study the effect of alternate wetting and drying, as well as of continuous drying, on the volume, weight, and dynamic Young's modulus of elasticity of portland blast-furnace cement concretes. Identical experiments were carried out with normal portland cement concretes so that the results for each type of cement used might be compared with one another. Two types of portland blast-furnace cement-one is of high slag content (65% slag by weight) and the other of low slag content (45% slag by weight) -were used in making concretes used in the experiments. The following results were obtained : 1. In drying shrinkage there was no difference between portland blast-furnace cement concretes and normal portland cement concretes, regardless of water-cement ratio, the length of curing period, and the amount of entrained air.2. When stored in water, portland blast-furnace cement concretes showed a greater expansion than normal portland cement concretes.3. The change in volume and weight of concretes caused by alternate wetting and drying had little relation to the type of cement used. In the change in dynamic Young's modulus of elasticity caused by the same process, however, the tendencies showed by portland blastfurnace cement concretes and normal portland cement concretes were markedly different from one another.