Hydration Reaction of Cementitious Composites with Calcium Silicate Slag

Calcium silicate slag (CSS) is a secondary solid waste produced during the extraction of aluminum oxide (Al2O3) from fly ash. Pulverized CSS can replace part of portland cement as a supplementary cementitious material. This study investigates the content of chemically bound water and the hydration degree of a CSS-cement system while varying the CSS content, water- binder ratio, and hydration age. Results show that adding CSS can appropriately reduce the content of chemically bound water and the hydration degree. A cube hydration model suitable for the CSS-cement system was established, which considered the spatial distribution and the evolution of cement and CSS particles in the hydration unit. Based on the cubic hydration model, the growth process of hydration products of CSS and cement particles was analyzed, the expression for the volume of CSS and cement particles at different hydration stages was deduced, and the hydration degree of the CSS-cement system was calculated. The calculated value of the hydration degree was compared with the test value to verify the correctness of the former. Overall, the results provide a practical experimental and theoretical framework to understand the application of the CSS-cement system.