Mechanistic Insights into Full 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 demonstrate that in the SR-CS activator system, which combines with desulfuriation gypsum as sulfate activator, increasing CS content elevates the normal consistency water demand due to the high-polarity, low-solubility Ca(OH) in CS. The SR-CS activator accelerates the early hydration process of cementitious materials, shortening the paste setting time while achieving compressive strengths of 17 MPa at 7 days and 32.4 MPa at 28 days, respectively. Higher fly ash content reduced strength owing to increased unreacted particles and prolonged setting. Conversely, desulfurization gypsum exhibited a sulfate activation effect, with compressive strength peaking at 34.2 MPa with 4 wt% gypsum. Chloride immobilization by C-S-H gel was confirmed, effectively mitigating environmental risks associated with SR. This work establishes a sustainable pathway for developing low-carbon cementitious materials using multi-source solid wastes.