The hydration of hydraulic active calcium germanates: Part 2. The early hydration of dicalcium germanate

The reactivity of Ca₂GeO₄ with water is very small compared with that of tricalcium germanate but similar to that of dicalcium silicate. Only one maximum of heat evolution is visible at the beginning of hydration. The initial reactivity of dicalcium germanate is followed by a period of very slow reactivity. The hydration products are the same as these formed with tricalcium germanate. Crystalline calcium hydroxide is present, and also at least two crystalline calcium silicate hydrate phases. The small reactivity of dicalcium germanate is influenced by the structure and by a reaction layer. This layer comprises hydration products, which cover the surface of dicalcium germanate and form a barrier whose permeability determines the kinetics of hydration.