Calcium hydroxide content and hydration degree of cement in cementitious composites containing calcium silicate slag.

Calcium silicate slag (CSS) is a secondary solid waste produced by the technology of extracting Al2O3 from fly ash. CSS was used in the present study to replace part of the cement to prepare cementitious composites. The calcium hydroxide (CH) content of the cementitious composites containing CSS (including the CH content produced by cementitious composites hydration, consumed by pozzolanic reaction of CSS, and residual in cementitious composites) and the hydration degree of cement are analyzed by observing the phase, content, and microscopic of CH. Results show that different replacement rates of CSS can reduce the CH content by approximately 7.59%-53.93%, which is determined by the mineral composition of CSS and its pozzolanic properties. In addition, the incorporation of CSS increases the hydration degree of the cement in the cementitious composites. This research can provide a new way for the utilization of CSS.