Mohsin Ali
Sewage sludge ash (SSA) offers a sustainable approach to waste valorization and low-carbon construction through its use in alkali-activated materials (AAMs). This review examines current research on SSA's chemical composition, pozzolanic reactivity, and role as a supplementary precursor in binder systems. Calcination at 850 °C enhances amorphous content and reactivity, promoting the formation of N-A-S-H and C-A-S-H gels when combined with fly ash, slag, or red mud. These gels are central to strength and durability, though performance is strongly influenced by precursor type, activator dosage, and curing conditions. Studies indicate that incorporating SSA can improve mechanical properties while reducing the carbon footprint of construction materials. However, unresolved challenges remain, including leaching risks, durability under varied environments, and the absence of standardized mix designs. Overall, SSA-based geopolymers show significant potential as eco-friendly alternatives to cement, but further research is required to establish safe, durable, and scalable applications.