Effect of nano-silica on hydration and conversion of calcium aluminate cement

Abstract

This study investigated the effect of nano-silica on the hydration and conversion of calcium aluminate cement (CAC). The specimens were exposed to 60 degrees C to accelerate the transformation of hydrates in CAC after initial curing at 20 degrees C. At an early stage of curing, adding nano-silica in CAC mitigated the formation of C(3)AH(6) and AH(3). At 1 day after exposure to 60 degrees C, the compressive strength reduction was observed in all specimens, and it was closely related to the conversion of CAH(10). That is, the conversion of all specimens occurred at 28 days after exposure, which resulted in a reduction in compressive strength. However, adding nano-silica mitigated the conversion from metastable phases (CAH(10) and C(2)AH(8)) to stable phases (C(3)AH(6) and AH(3)). As a result, the extent of compressive strength loss could be reduced by the formation of stratlingite (C(2)ASH(8)) in the case of 4% addition of nano-silica. In conclusion, adding nano-silica in CAC was effective regarding structural integrity by delaying the conversion of metastable hydrates, as well as maintaining the long-term strength of CAC by forming stratlingite. (C) 2018 Elsevier Ltd. All rights reserved.