Preparation of magnesium phosphate cement by salt lake magnesium slag and its hydration process

Abstract

Magnesium phosphate cements (MPC) have shown promising applications in many fields, but high raw material prices hinder their development. The production of salt lake MPC (SLMPC) from magnesium slag (MS), a byproduct of lithium extraction from salt lakes, offers significant environmental and economic advantages. In this study, a low-cost magnesia raw material was obtained through the calcination of MS, which was subsequently utilized in conjunction with KH₂PO₄ to prepare SLMPC. The changes in hydration products, microscopic morphology, solution pH value, and TG content during the SLMPC curing process, and the hydration kinetics equation and model were used to study the hydration processes of SLMPC. The results show that the outcome indicates that the SLMPC system entered the accelerated reaction stage within 6 min after mixing, where the highest heat release rate was 6.29 J·g⁻¹·min⁻¹, the maximum heat release was 205.3 J·g⁻¹, and the main hydration product appeared at 50–60 min. The hydration behavior of SLMPC exhibits similarities to that of traditional MPC. Specifically, the acceleration phase is governed by an autocatalytic reaction, the deceleration phase is influenced by both autocatalytic reactions and diffusion processes, and the stabilization phase is predominantly controlled by diffusion mechanisms. This paper aims to establish the theoretical foundation for the industrial application of MS and the cost-effective production of MPC.