Physicochemical Study of the Self-Disintegration of Calcium Orthosilicate (β→γ) in the Presence of the C(12)A(7) Aluminate Phase

The β-γ polymorphic transition of calcium orthosilicate (C(2)S) is a key phenomenon in cement chemistry. During this transition, the compound expands due to structural changes and a significant reduction in its density is observed, leading to its disintegration into a powder with a very high specific surface area. Owing to this tendency of the C(2)S material to “self-disintegrate”, its production is energy-efficient and thus environmentally friendly. A physicochemical study of the self-disintegration process was conducted with the aim of determining how the amount of dodecacalcium hepta-aluminate (C(12)A(7)) in calcium orthosilicate (C(2)S) affects the temperature at which the polymorphic transi-tions from α’L-C(2)S to β-C(2)S and from β-C(2)S to γ-C(2)S undergo stabilization. The applied techniques included differential thermal analysis (DTA), calorimetry and X-ray diffraction (XRD), and they made it possible to determine what C(2)S/C(12)A(7) phase ratio in the samples and what cooling rate constitute the optimal conditions of the self-disintegration process. The optimal cooling rate for C(2)S materials with a C(12)A(7) content of up to 60 wt% was determined to be 5 K·min(−1). The optimal mass ratio of C(2)S/C(12)A(7) was found to be 70/30, which ensures both efficient self-disintegration and desirable grain size distribution.