The chemistry of the pore fluid of silica fume-blended cement systems

Abstract

The behaviour of silica fume in cement systems, particularly, the pozzolanic reaction was investigated by monitoring the chemistry of the pore solution of silica fume-blended cement pastes. This was supported by heat of hydration studies on similar mixes. Silica fume accelerated cement hydration during the early hours. The increased rate of hydration is believed to be due to enhanced precipitation of hydration products on the submicroscopic silica fume particles which possibly served as nucleation sites for crystallization during the early hours when it existed as chemically inert filler. The study also revealed evidence of pozzolanic reaction within three days after the formulations of the mixes, irrespective of the water-to-binder ratio used. This evidence is apparent in blends made with portland as well as blastfurnace slag cements. In both cases, OH −, Ca 2+, K +, and Na + were chemisorbed from the cement solution.