Effect of curing temperature on the nonevaporable water in portland cement blended with geothermal silica waste

This paper reports the results of the utilization of a silica waste from a geothermal power generation plant as partial replacement of portland cement. To evaluate the reactivity of the silica waste, the effect of the curing temperature was analyzed by means of the estimation of nonevaporable water (NEW) and calcium hydroxide (CH) contents. Pastes of portland cement substituted with 0%, 5%, 10% and 15% of geothermal silica waste (GSW) and water/solid ratio of 0.50 were cured at 10, 20, 40 and 60 °C for up to 540 days. The pastes were characterized by thermogravimetric analysis. According with the CH estimations, the geothermal silica showed a strong pozzolanic behavior. Nevertheless, the NEW contents were lower compared to those of neat cement, in agreement with other reports. The results of NEW contents of neat and blended cements were processed to obtain a modified NEW (mNEW) that excluded the water corresponding to the CH. The mNEW data indicated that the blended cements reached higher contents of nonevaporable water.