Effect of curing on water permeability of concretes prepared with normal Portland cement and with slag and silica fume

The effect of curing on the coefficient of permeability of concretes was studied. Concretes, grades 35 and 40, were prepared from a normal Portland cement and from a high slag blended cement. The effect of the addition of silica fume to both of these binders was also studied The water permeability of various concretes was measured using the constant flow method. The coefficient of permeability was evaluated for concretes subjected to three types of curing: samples were continuously moist cured for 7 or 28 days, or were subjected to 28 clays of intermittent curing. Twenty-eight days of intermittent curing was found to be as effective in reducing permeability as 7 clays of continuous moist curing. Twenty-eight days of continuous moist curing gave the lowest coefficient of permeability. The addition of silica fume to normal Portland cement considerably reduced the permeability, and concretes prepared with high slag blended cement had lower permeability than did those prepared with normal Portland cement.