Calorimetry of Portland cement with silica fume, diatomite and quartz additions

The present paper analyses the influence of three siliceous mineral admixtures or mineral additions, on hydration reactions of two Portland cements with very different mineral composition, but focussing it on the heat hydration parameter, mainly. The main techniques used in the study were conduction calorimetry and Frattini test and the ancillary analytic tests included the determination of setting times and the chemically combined water amount as well as X-ray diffraction analysis of the plain PC and their blended cement pastes. The results show how size, morphology and crystalline or vitreous state of the siliceous mineral additions affect its pozzolanicity and hydraulicity and, concomitantly, the hydration reactions in Portland cements with widely varying mineralogical characteristics. On the other hand, the findings also differentiate the effects of direct, non-direct and indirect stimulation of the hydration reactions by these siliceous mineral admixtures. In addition, it is sustained that when these types of effects occur jointly under certain conditions, they may induce results that can be regarded to be the comparable to a Calorific Synergic Effect. (C) 2009 Elsevier Ltd. All rights reserved.