Preparation and accelerated carbonation of low temperature sintered clinker with low Ca/Si ratio

A novel clinker with low Ca/Si ratio and low sintering temperature was synthesized, and the property of the clinker was tested. A clinker sintered from industrial raw materials mainly contains rankinite (Ca₃Si₂O₇), pseudowollastonite (Ca₃(Si₃O₉)) and ferrosilite ((Ca,Mg,Fe,Al)₂Si₂O₆). Quantitative analysis of the mineral composition was performed via X-ray powder diffraction using the Rietveld method. Results showed that the optimal formation region of the clinker was at 1300 °C for 4 h, resulting in a Ca/Si ratio of 1.27 and 72.7% rankinite, 24.6% pseudowollastonite and 2.7% ferrosilite. The hardening of the clinker occurred mainly due to the carbonation of rankinite and pseudowollastonite yielding CaCO₃ and SiO₂. Carbonation depth was determined using confocal laser scanning microscopy (CLSM). Experiments indicated that the carbonation depths of the clinker in accelerated carbonation conditions were 659 ± 20 μm, 787 ± 18 μm and 1118 ± 98 μm for 1, 3, and 28 days of carbonation, respectively. Moreover, well-developed calcite crystals could form a network-like and inter-connected structure, further enhancing its performance.