Effects of Calcium Silicate Slag on Hydration of Cementitious Pastes

Abstract

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.

Experimental Study on Subgrade Material of Calcium Silicate Slag

“…Bai et al [ 17 ] showed that CSS promoted the degree of hydration of cement, and that the hydration of β-C 2 S to produce Ca(OH) 2 decreased with the increasing substitution of CSS. Shi et al [ 18 ] demonstrated the use of calcium silicate slag and blast furnace slag to prepare cementitious materials, and that the compressive strength could reach more than 65 MPa when CSS was dosed at 30% and cured for 28 d. Zhang et al [ 19 ] studied the hydration of cementitious materials based on CSS. Their results showed that as the CSS replacement rate increased, the chemically bound water decreased and the spherical gel observed in the microstructure decreased, which improved the degree of hydration and reduced the heat of hydration.…”