Chemical activation of calcium aluminate cement composites cured at elevated temperature

Abstract

The influence of sodium sulfate, as an activator, on the hydration of calcium aluminate cement (CAC)-fly ash (FA)-silica fume (SF) composites was investigated. Different mixes of CAC with 20% pozzolans (20% FA, 20% SF and 10% FA + 10% SF) were prepared and hydrated at 38 °C for up to 28 days. The hydration products were investigated by XRD, DSC and SEM. The results showed that sodium sulfate accelerated the hydration reactions of calcium aluminate cement as well as the reactions of FA and SF with CAH 10 and C 2AH 8 to form the strätlingite (C 2ASH 8). The later reactions prevent the strength loss by preventing the conversion of CAH 10 and C 2AH 8 to the cubic C 3AH 6 phase. The acceleration effect of Na 2SO 4 on the reactivity of fly ash was more pronounced than on the reactivity of silica fume with respect to reaction with CAH 10 and C 2AH 8 phases. © 2012 Elsevier Ltd. All rights reserved.