Investigations on the hydration of C3S with different water-solid ratios and subsequent carbonation

Hydration of synthesized C3S samples (93.7% C3S + 6.3% C2S) with different water-solid ratios and the subsequent carbonation of the hydration products (mainly hydrated calcium silicate (C-S-H)) were investigated through FTIR, TG, and XRD experiments. It was observed that a higher water-solid ratio induced a faster hydration rate of C3S and a higher amount of C-S-H, but the C-S-H was found to have a higher carbonation rate because of a looser microstructure and a lower Ca/Si ratio compared to that in low water-solid groups. In addition, the carbonation products CaCO3 became less stable in the high water-solid groups, and changed from calcite to aragonite with increasing water-solid ratios. However, upon surpassing a particular threshold of the water-solid ratio, both the hydration rate of C3S and the carbonation rate of C-S-H became stable. This study could provide a better understanding on key factors influencing cement hydration and C-S-H carbonation.