The changes in the reaction kinetics and phase assemblage of sodium silicate-activated CaO-MgO-Al2O3-SiO2 glasses induced by the Al replacement by Mg

Abstract

Although intensive research was done on the impact of slag chemistry on the reaction kinetics of alkali-activated materials, its role remains unclear due to the slag's uncontrolled oxides variations. This research investigated the role of the Al replacement by Mg on the reaction kinetics and phase assemblage of sodium silicate-activated calcium‑magnesium-aluminosilicate (CMAS) glasses by a novel approach. The calcium-aluminosilicate (CAS) glass reacted faster than the CMAS ones. Also, increasing the replacement level in the CMAS glasses slightly accelerated the reaction but considerably increased the total heat. Katoite and strätlingite precipitated at high Al2O3 wt% of 20 and 25, respectively. A decrease in the total volume of the hydrates was predicted by thermodynamic modelling and further supported by gas adsorption measurements. The paper's outcomes aid in providing a fundamental understating of the effect of Al and Mg which could help with customising the mix design for enhanced performance of alkali-activated binders.