Effect of aluminum impurities within water glass on the compressive strength and hydration of alkali-activated slag

To address the significant CO 2 emissions of commercial water glass, the utilization of alkali activators prepared from waste glass is a viable solution. However, it is important to note that these activators frequently contain aluminum (Al) impurities, which have been reported to affect the initial dissolution behavior of slag. But the impact of Al impurities on the compressive strength and hydration of alkali-activated slag remains inadequately understood. Consequently, the compressive strength, hydration, hydration products, calcium aluminosilicate hydrate gel properties, and pore structure of slag activated by water glass containing different concentrations of Al impurities were investigated. The findings reveal that Al impurities in water glass cause a reduction and delay in the second exothermic peak, regardless of slag composition. Despite this, their long-term influence on pore structure, compressive strength, and phase assemblage is minimal and can be considered negligible across different types of slag. • Aluminum impurities in water glass retard early-stage slag dissolution and hydration kinetics • 3-day cumulative heat release is nearly unaffected despite early-stage inhibition • Aluminum impurities have negligible effects on strength and microstructure • Aluminum impurities exhibit similar effects on hydration kinetics and products across different slags