Effect of Calcination Temperature on the Reactivity of Lithium Slag Powder as a Supplementary Cementitious Material

Lithium slag powder (LSP), a by-product of lithium extraction, has attracted increasing interest as a supplementary cementitious material (SCM) due to its aluminosilicate-rich composition and growing availability. However, its limited intrinsic reactivity constrains direct use in cementitious systems. This study systematically investigates the effect of calcination temperature on the physicochemical properties, pozzolanic reactivity, and cement hydration performance of LSP. LSP was thermally treated at 300–900 °C, and structural and morphological changes were characterized using X-ray diffraction, scanning electron microscopy, and Fourier-transform infrared spectroscopy. The reactivity of calcined LSP was quantitatively assessed through isothermal calorimetry (R3 test), thermogravimetric and derivative thermogravimetric analysis. Chapelle testing, leaching tests, and compressive strength measurements of cement mortars. Controlled calcination was found to enhance the intrinsic reactivity and pozzolanic activity of LSP, resulting in improved long-term mechanical performance. The findings provide mechanistic insights and practical guidance for the sustainable use of lithium slag as an SCM in cement-based materials.