Hydration of Portland cement in presence of silica fume

The hydration of ordinary Portland cement at room temperature was studied in the presence of silica fume. The silica fume content was 0, 5, 10, 15 and 20 wt% of the weight of cement for all mixtures. The mixtures were stirred in 100 ml deionised water for different time intervals up to 7 days. The filtered solutions were analysed for pH, silicon and calcium ions. Most of the calcium hydroxide released during the hydration of Portland cement had reacted with the silica fume within 7 days. The X-ray diffraction and scanning electron microscopy studies on the hydration products showed a considerable reduction in the amount of calcium hydroxide as a result of its reaction with silica fume. The optimum condition was obtained by the addition of 20% silica fume.