Effects of Calcium to Silicon Ratios on Accelerating Carbonation of Calcium Silicate Hydrate

In order to clarify the mechanism of carbonation of waste cement mineral, the effect of calcium to silicon (C/S) ratio on the accelerated carbonation of calcium silicate hydrate (C­S­H) was investigated.The results show that the C/S ratio has an effect on the carbonation of C­S­H, and the mass gain increases but the degree of carbonation decreases with the increase of C/S ratio.The larger pore size leads to a higher carbonation rate.Aragonite, vaterite and calcite coexist in the carbonation product.Aragonite appears when the C/S ratio≤0.67.The maximal mole fraction of vaterite appears when the C/S ratio0.83.Calcite gradually dominates as the C/S ratio≥1.00 increases.The decomposition of calcium carbonate occurs in two temperature ranges (i.e., 400­620and 650­800), and most of aragonite and vaterite are subjected to the decomposition in the low temperature range, and calcite forms in the carbonation process at a higher decomposition temperature.