Calcium silicate slag (CSS) is waste slag and it contains a large amount of beta-dicalcium silicate. This study is mainly focused on the effect of CSS on the hydration of cementitious pastes. CSS was used to partly replace cement, and composite pastes containing CSS and cement were prepared. The mineral composition and particle size distribution of CSS were characterized. The chemically combined water of the paste sample was measured at a given test age. Based on the value of chemically combined water, the hydration degree and the hydration rate of composite pastes were analyzed. The flexural strength of the samples was established. The pore structure and micromorphology of the sample were also observed. The results indicate the chemically combined water decreased, the hydration degree decreased, the hydration rate declined, and the spherical micromorphology of the calcium silicate hydrate gel was reduced after more cement was replaced by CSS in the composite pastes. Besides, the amount of pores increased, its size was bigger, and air content in the pore was higher. However, flexural strength was lower. CSS has a significant impact on the hydration of cementitious pastes, and it is thus suitable to regulate hydration.
Keywords: beta-dicalcium silicate; calcium silicate slag; cementitious pastes; chemically combined water; flexural strength; micromorphology; pore structure.