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.