Effect of sodium silicate content on shrinkage and mechanical properties of MGO-activated slag

Abstract This study investigates the effect of MgO and sodium silicate as composite activators on the hydration behavior, mechanical properties, and autogenous shrinkage of alkali-activated slag (AAS). The results show that using MgO as the sole activator leads to lower compressive strength due to its weak alkaline environment, resulting in a limited degree of slag hydration. However, MgO effectively mitigates autogenous shrinkage by promoting the formation of hydrotalcite-like phases. The incorporation of sodium silicate significantly enhances compressive strength by providing a higher pH environment, accelerating slag dissolution, and facilitating the formation of C-S-H. Nevertheless, this rapid hydration process increases autogenous shrinkage. The combined use of MgO and sodium silicate provides a balance between mechanical performance and shrinkage control, offering a theoretical basis for the development of durable alkali-activated materials.