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 w as studied. Concretes, grades 35 and 40, were prepared from a normal P ortland 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 constan t flow method. The coefficient of permeability was evaluated for concr etes subjected to three types of curing: samples were continuously moi st cured for 7 or 28 days, or were subjected to 28 clays of intermitte nt curing. Twenty-eight days of intermittent curing was found to be as effective in reducing permeability as 7 clays of continuous moist cur ing. Twenty-eight days of continuous moist curing gave the lowest coef ficient of permeability. The addition of silica fume to normal Portlan d cement considerably reduced the permeability, and concretes prepared with high slag blended cement had lower permeability than did those p repared with normal Portland cement.