Green Disposal of Domestic Wastewater in Alkali-Activated Slag Mortar: Enhancing Performance and Sustainability

Abstract

The global increase in water consumption has led to significant domestic wastewater (DW), with only 55.5% being treated properly. Discharging untreated DW has serious environmental consequences and wastes a valuable resource. Therefore, this study proposed replacing 25%–100% potable water with DW in preparing alkali-activated slag (AAS) mortars. The results indicated that the use of DW promoted the hydration of AAS. Pore structure analysis revealed that DW enhanced the formation of gel pores while reducing mesopores, resulting in a higher elastic modulus and a denser microstructure of AAS mortars. Consequently, the compressive strength of AAS mortars increased by 9.0%–20.3%, and the autogenous shrinkage decreased by 7.5%–34.5%. Moreover, replacing 100% of potable water with DW maximizes its utilization and improves the cost–benefit and eco-efficiency of AAS mortars by 9.4% and 10.0%. These findings demonstrate the feasibility of using DW as mixing water for AAS mortars, offering a sustainable approach to the utilization of DW.