Kinetics and mechanism of hydration of blended cement pastes containing silica fume at different porosities

ABSTRACT

The industrial wastes such as silica fume and blast-furnace slag or by- product as cement kiln dust cause many environmental and health hazards and represent a burden for all factories, nowadays. In the present work, granulated slag and raw [or washed] cement kiln dust were used to make blended cement. Silica fume was utilized as a partial substitute for slag. Past-hydration of the various slag- cement dust-silica fume mixtures was carried out at room temperature for different curing periods. The initial water/solid ratios used were 0.30, 0.40 and 0.50. From the results of combined water and free lime contents of the hardened pastes at various hydration ages, the mechanism of the hydration process could be specified. The beginning and duration of each hydration period depended primarily on the amount of silica and the porosity of the paste