Experimental investigation and theoretical modeling of silica fume activity in concrete

Silica fume was used as additive in mortar, replacing part of the volume of either Portland cement or aggregate. In a series of experiments, the development of the strength, porosity, bound water, and calcium hydroxide content was measured. The silica fume addition in both cases gave higher strengths than the control mixture. The bound water content and porosity were finally the same as for the control mixture in the case of the aggregate replacement. On the basis of the experimental results, the chemical reaction of the silica fume in hydrating cement is proposed. Using this equation and the cement hydration reactions, quantitative expressions for estimation of the chemical composition, porosity, and, indirectly, strength and durability of a silica fume-concrete are proposed. (C) 1999 Elsevier Science Ltd. All rights reserved.