Synergistic activation of lithium slag using solid-waste-derived alkali and sodium sulfate: Towards high-performance low-carbon cementitious materials

The low reactivity of lithium slag (LS) pose significant challenges for its resource recovery. This study investigated a synergistic activation strategy for granulated blast furnace slag-LS, employing kambara reactor desulfurization ash (KRDA) as a solid-waste-derived alkali source, complemented by sodium sulfate (SS) as a chemical activator. The effects of SS dosage (expressed as Na2O equivalent) on hydration characteristics, microscopic morphology and compressive strength were systematically investigated. The results demonstrated that SS, by reacting with portlandite from KRDA to form NaOH and CaSO4, elevated the system alkalinity and enhanced ion leaching. This effectively dissolved the silica-alumina phases in LS and refined the chemical structure of the gels. An optimal SS dosage (2%, mass of Na2O equivalent to the total solid mass) markedly enhanced early hydration, promoting the synergistic formation of AFt/U-phase and denser C-(A)-S-H gels. This yielded compressive strengths of 24.7 MPa and 38.5 MPa at 3 days and 28 days, representing increases of 135.2% and 70.4%, respectively, over the SS-free sample. However, excessive SS (>2%) induced significant U-phase decomposition and microcracking at later ages, impairing long-term performance. A simplified life cycle assessment revealed that the developed binder reduced global warming potential by 95.13% and total cost by 48.42% compared to Portland cement. This work elucidates a promising activation mechanism and presents a feasible high-value pathway for co-utilizing LS and KRDA in sustainable, low-carbon cementitious materials.