Sewage sludge ash (SSA) is a waste material obtained from wastewater treatment plants that has a sufficient proportion of SiO2, Al2O3, and CaO, which can be used in alkali-activated mortar (AAM) applications. This study investigates the utilization of SSA as a binder in AAM and examines the impact of varying alkaline solution molarity, silica fume (SF) content, and blast furnace slag (BFS) addition on compressive strength. Findings indicate that SSA exhibits high water absorption, leading to its limited reactivity and weak bond with the alkaline solution. The addition of 50% SF not only enhances bonding but also achieves a compressive strength of 11 MPa within 7 days, while variations in alkaline solution molarity (ranging from 8M to 16M) show limited influence on strength. Reducing SF content to 30% results in a lower strength of 8 MPa within 7 days. However, even with SF addition, achieving a compressive strength of 20 MPa within 7 days remains a challenge. The addition of 50% BFS proves highly effective, achieving 20 MPa within 7 days and 38 MPa without the need for oven curing. Additionally, the study explores the effects of different molar ratios of the alkaline solution and the chemical compositions of supplementary materials (Na2O/SiO2, H2O/Na2O, and SiO2/Al2O3) on compressive strength and explains the impact of these ratios on strength. With a well-optimized mix design, SSA proves to be a viable component in AAM mortars.