Effects of bauxite tailings and sodium silicate on mechanical properties and hydration mechanism of magnesium phosphate cement

•MPC was modified by bauxite tailings and sodium silicate.•Sodium silicate improved the compressive strength, water resistance of MPC.•Bauxite tailings and sodium silicate made MPC matrix more compact. Aiming at the problem of poor water resistance of magnesium phosphate cement (MPC) and large amount of bauxite tailings (BTs) accumulation, the effects of BTs and sodium silicate (NA) on mechanical properties and the hydration mechanism of MPC are investigated. The experimental results show that adding 15.0 wt% BTs can decrease the production cost without decreasing the strength of MPC, while NA can enhance the strength and water resistance of MPC with BTs, delay the setting time, and decrease the cumulative heat release during hydration. The compressive strength reaches 42.6 ± 0.4 MPa after curing in air for 28 d. Microanalysis shows that the main hydration product is struvite-K (MgKPO4·6H2O). NA can activate BTs, release silicon and aluminum components from BTs, and produce the zeolite-like hydration product sodium silicate aluminate hydrate (N-ASH) gel. Adding BTs and NA to MPC reduces the generation of microcracks and makes matrix more compact. Therefore, this work not only improves MPC performance, but also promotes the resource utilization of BTs.