Hydration of cement and silica fume paste

Abstract

The objective of this study was to determine the changes in the hydration process of cement paste as increasing amounts of silica fume are incorporated at high and low w/(c+sf) ratios. The hydration process of cement/silica fume paste was followed from the estimation of heat of hydration, Ca(OH) 2 content, and non-evaporable water. These quantities were estimated at w/c+sf ratios of 0.48 and 0.28 for silica fume content increasing from 0 to 25%. The hydration study indicated that the hydration reaction of the cement is altered due to the presence of silica fume. At both w/c+sf ratios the initial maximum rate of heat of hydration is reduced due to the presence of silica fume. At the higher w/c+sf ratio, silica fume appears to accelerate the hydration of cement, this effect is not significant at the lower w/c+sf ratio. A higher dosage of silica fume was required to consume all the Ca(OH) 2 at the higher w/c+sf ratio, since the amount of Ca(OH) 2 produced at the higher w/c+sf ratio is greater. A large proportion of the pozzolanic reaction takes place as early as 3 days. Although the pozzolanic reaction was found to continue up to 180 days, the amount taking place after 28 days is relatively small.