Synthesis of backfill foam lightweight soil from bauxite tailings slurry and industrial byproducts

• A regression equation linking actual water content and mud-water separation rate enables efficient characterization of bauxite tailing slurry for downstream utilization. • Fly ash reduces workability and compressive strength of foam lightweight soil, while slag powder markedly enhances compressive strength (up to 58.54%) and improves long-term water stability and carbonation resistance. • Microstructural analyses (XRD, SEM-EDS, TG-DSC) reveal that fly ash decreases hydration degree, whereas slag powder optimizes pore structure and densifies the skeleton of the lightweight soil. • This approach offers a sustainable route for recycling bauxite tailings and industrial byproducts into construction materials, yielding socio-economic and environmental benefits.