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

The hydration of synthesised C₃S samples (93.7% C₃S + 6.3% C₂S) with different water–solid ratios (WSRs) and the subsequent carbonation of the hydration products (mainly hydrated calcium silicate (C-S-H)) were investigated using Fourier transform infrared spectroscopy, thermogravimetric analysis and X-ray diffraction. It was found that a higher WSR induced a faster hydration rate of C₃S and a greater 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 calcium/silicon ratio compared with that in the groups with a low WSR. In addition, the carbonation product calcium carbonate became less stable in the high-WSR groups, and changed from calcite to aragonite with an increase in the WSR. However, upon surpassing a particular threshold of the WSR, both the hydration rate of C₃S and the carbonation rate of C-S-H became stable. The results of this study could provide a better understanding of the key factors influencing cement hydration and C-S-H carbonation.