Abstract
Composition of cement hydration products in concretes made with two condensed silica fumes, three pulverized fly ashes (PFA), and one ground granulated blast furnace slag, and stored at 38°C and 100% relative humidity for 3 years was analyzed using an electron probe microanalyzer. The pore solution expression method was also applied on pastes to analyze the composition of the pore water. The mean CaO/SiO 2 (C/S) mole ration of hydrates in the ordinary Portland cement (OPC) control concrete was 2.05. In blended concretes, this ratio decreased to between 1.24 and 1.46, however with no clear distinction from one supplementary cementing material (SCM) type to another. All blended pastes except the one with the very alkalirich PFA tested showed a drop in the alkali concentration of the pore solution compared with the control paste. Mass balance calculations indicated that lower C/S hydrates produced in the presence of SCM can contain much more alkali than OPC hydrates, provided that more alkali is available. These SCMs may decrease the alkalinity and the pH of the pore solution, and reduce expansion due to alkali silica reactivity.
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