Enhanced hydration and mechanical properties of cement-based materials with steel slag modified by water glass

Substitution of cement clinker with steel slag (SS) is an effective approach for solving the problems of environmental contamination and resource consumption caused by cement manufacturing. This study aimed to improve the mechanical properties of cement–SS mortar by incorporating water glass (WG) to promote the optimal utilization of SS waste. In this study, the setting time, mechanical strength, and microstructure of cement–SS systems were investigated. From the experimental results, it was found that the incorporation of WG effectively shortened their setting times and enhanced their mechanical strengths, particularly early strengths. The enhancement in these properties was mainly due to the acceleration effect of WG on the cement–SS system hydration process by expediting the dissolution of the tetrahedron [SiO4] and [AlO4] units in SS to produce H3SiO4− and H3AlO42−. This facilitated the formation of more stable zeolite-like hydration products. Furthermore, the soluble Si4+ supplied by WG reacted with Ca (OH)2 to form a calcium silicate hydrate (C–S–H) gel. Both the high hydration degree of SS at early ages and C–S–H gel formation appeared to be the primary mechanisms for the strength improvement of the cement–SS systems by WG addition.