Physicochemical Study of the Self-Disintegration of Calcium Orthosilicate (β→γ) in the Presence of the CA Aluminate Phase.

The β-γ polymorphic transition of calcium orthosilicate (CS) 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 CS 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 (CA) in calcium orthosilicate (CS) affects the temperature at which the polymorphic transi-tions from α'L-CS to β-CS and from β-CS to γ-CS undergo stabilization. The applied techniques included differential thermal analysis (DTA), calorimetry and X-ray diffraction (XRD), and they made it possible to determine what CS/CA phase ratio in the samples and what cooling rate constitute the optimal conditions of the self-disintegration process. The optimal cooling rate for CS materials with a CA content of up to 60 wt% was determined to be 5 K·min. The optimal mass ratio of CS/CA was found to be 70/30, which ensures both efficient self-disintegration and desirable grain size distribution.