Mechanistic Insights into All-Solid-Waste Activators for Enhancing the Performance of Blast Furnace Slag-Fly Ash Cementitious Composites

To address the practical limitations of conventional alkaline activators (e.g., handling hazards, cost) and promote the resource utilization of industrial solid wastes, this study developed a novel all-solid-waste activator system comprising soda residue (SR) and carbide slag (CS). The synergistic effects of SR-CS activators on the hydration behavior of blast furnace slag (GGBS)-fly ash (FA) cementitious composites were systematically investigated. Mechanical performance, phase evolution, and microstructural development were analyzed through compressive strength tests, XRD, FTIR, TG-DTG, and SEM-EDS. Results revealed that the SR-CS activator (22 wt% SR, 8 wt% CS) significantly enhanced early hydration kinetics, yielding 7-day and 28-day compressive strengths of 17 MPa and 32.4 MPa, respectively. Fly ash substitution reduced strength due to unreacted particles, while desulfurization gypsum (DG) exhibited a sulfate activation effect, peaking at 4 wt% DG (34.2 MPa). Chloride immobilization by C-S-H gel was confirmed, addressing environmental concerns associated with SR. This work provides a sustainable pathway for developing low-carbon cementitious materials using multi-source solid wastes.