Insights into the carbonation behavior of polymorphs of Ca₂SiO₄ (C₂S) : the role of calcination temperature

Abstract

Dicalcium silicate is a key carbonatable mineral in Portland cement. Typically, pure C2S is synthesized through high-temperature solid-phase reactions above 1400 °C, but such temperatures can negatively affect its carbonation behavior, with the underlying mechanisms remaining unclear. This study investigated the effect of calcination temperatures (600 °C to 1400 °C) on C2S carbonation. Results show that high calcination temperatures significantly reduce carbonation reactivity and CO2 uptake. This is primarily due to the increase in particle size, the transformation from fibers to particles, and a decrease in specific surface area. Additionally, the internal crystal defects in low-temperature calcined C2S contribute to its high reactivity. However, the temperature-induced reduction in mesoporosity, increase in crystal size, decrease in defects, and phase transition from β-C2S to γ-C2S also affect carbonation reactivity. These factors also influence the polymorphs and morphology of CaCO3. This study offers guidance for developing low-temperature synthesis methods for low-calcium cement.