Lithium slag-based geopolymer synthesized with hybrid solid activators

Abstract

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-ASH 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.