Effects of Microsilica (Silica Fume) on Pore‐Solution Chemistry of Cement Pastes

Pore solutions expressed from hydrated Portland cement pastes containing up to 30% microsilica (silica fume) as replacement for cement were analyzed. The presence of microsilica enhances early concentrations of alkalies and hydroxyl ions, but after 1 day the effect is reversed, and the concentrations of these ions are progressively reduced to very low values. Alkali reduction seems more pronounced for pastes of higher water content, and low levels of microsilica replacement (5 or 10%) exert substantially greater than proportional effects.