Lithium slag-based geopolymer synthesized with hybrid solid activators

Lithium slag (LS) is a kind of solid waste in the lithium product industry. Nowadays, the amount of LS has increased sharply due to the popularity of lithium batteries; however, the recycling of LS is rare. In this research, LS was used to prepare the one-part geopolymer by three hybrid solid activators: NaOH + Na₂SiO₃, NaOH + Ca(OH)₂, and NaOH + CaCO₃. The effects of such hybrid activators on the workability, mechanical property, hydration process, microstructure, and pore structure of the formed one-part geopolymer samples were investigated. Experimental results showed that the LS-based geopolymers with 5 % of the hybrid activator could obtain moderate mechanical properties (The maximum 28d compressive strength can reach 35.6 MPa). Ca(OH)₂ and CaCO₃ had lower alkalinity than Na₂SiO₃, but they exhibited superior effects when combined with NaOH. Ca-based activators increased the reaction degree of the hardened paste, leading to generating more C-A[sbnd]S[sbnd]H gel. Besides, the pore structure of the formed geopolymers was also refined. Compared with Na₂SiO₃ and Ca(OH)₂, CaCO₃ is more suitable for preparing the NaOH activated LS-based geopolymer.