Physicochemical Study of the Self-Disintegration of Calcium Orthosilicate (β→γ) in the Presence of the C12A7 Aluminate Phase

The beta-gamma polymorphic transition of calcium orthosilicate (C2S) 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 C2S 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 (C2S) affects the temperature at which the polymorphic transi-tions from alpha'L-C2S to beta-C2S and from beta-C2S to gamma-C2S undergo stabilization. The applied techniques included differential thermal analysis (DTA), calorimetry and X-ray diffraction (XRD), and they made it possible to determine what C2S/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 C2S materials with a C(12)A(7) content of up to 60 wt% was determined to be 5 K & BULL;min(-1). The optimal mass ratio of C2S/C(12)A(7) was found to be 70/30, which ensures both efficient self-disintegration and desirable grain size distribution.

Automated summary

The beta-gamma polymorphic transition of calcium orthosilicate (C2S) leads to its self-disintegration into a powder with a high specific surface area, making its production energy-efficient and environmentally friendly. A study found that the optimal conditions for self-disintegration of C2S materials with up to 60 wt% C(12)A(7) content included a cooling rate of 5 K·min(-1) and a mass ratio of C2S/C(12)A(7) of 70/30, ensuring both efficient self-disintegration and desired grain size distribution.