Calorimetric study of gamma dicalcium silicate during the accelerated carbonation process

Abstract This paper is focused on investigating the chemical processes during the carbonation of a gamma dicalcium silicate ( γ -C 2 S). Isothermal calorimetry, in particular, provides valuable insights into the heat flow associated with the carbonation process under controlled conditions. The carbonation reactivity of γ -C 2 S under varying CO 2 pressure and water-to-solid ratio (w/s) using isothermal calorimetry was examined. The influence of these parameters on the extent of the carbonation reaction and the resulting proportions of calcium carbonate polymorphs (calcite, vaterite, and aragonite) was explored. Furthermore, the carbonation products were characterized using X-ray diffraction analysis (XRD), thermogravimetric and differential thermal analysis (TG–DTA), and scanning electron microscopy (SEM) to provide a comprehensive understanding of the reaction mechanism and the properties of the formed products. The results indicated that the partial pressure of CO 2 had a limited influence on the carbonation degree, whereas the water-to-solid ratio greatly enhanced the extent of the reaction. Aragonite and calcite were identified as the predominant reaction products. Subsequent analyses at high temperatures revealed a transformation of aragonite into calcite at approximately 500 °C, followed by its decomposition into calcium oxide approximately at 800 °C.