Effect of Magnesium and Temperature on the Accelerated Carbonation Progress of β-Dicalcium Silicate.

This study investigates the impact of different temperatures and initial Mg/Ca molar ratios in the solution on the wet-accelerated carbonation of β-dicalcium silicate (β-CS). The x-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), thermogravimetric analyzer (TGA), and field emission scanning electron microscopy (FE-SEM) analysis results indicated that temperature and the Mg/Ca molar ratio are key factors in the nucleation of aragonite. Aragonite formed at a temperature above 60 °C, and the high temperature promoted the crystallinity of needle-like aragonite with a length of 1-6 μm and a diameter of ~1 μm. Moreover, 80 °C was the most favorable temperature for the formation of aragonite with a large aspect ratio in the carbonation system of β-CS. Mg had a significant effect on inhibiting the transformation of aragonite to calcite and promoting the stability of aragonite. Aragonite became the dominant CaCO polymorph instead of calcite when the Mg/Ca molar ratio was above 1.0, and pure aragonite-style calcium carbonate was formed at a Mg/Ca molar ratio of 1.5.