Thermo-Carbonation synergy for enhanced CO ₂ sequestration and performance of activated bauxite residue-based geopolymer composites

This study examines thermo-carbon curing of geopolymer composites using bauxite residue, a major mining waste from alumina production, with silica fume and ground granulated blast furnace slag. Bauxite residue calcined at 700 °C showed a 33.3% activity increase. Seven mixes with varying compositions underwent thermal curing and combined thermal–CO2 curing. Under thermal curing, the optimized mix achieved 48.48 MPa compressive strength at 28 days. Under combined curing, strength decreased due to carbonation-induced decalcification, stabilizing at 23.51 MPa, with up to 68% early loss. Nevertheless, durability improved, with sorptivity reduced by 29.54% and drying shrinkage lowered from 4765 to 3916 µm/m. Maximum CO2 uptake reached 5.87% by mass and 2.08% by TGA. Microstructural analysis confirmed gel decalcification, pore coarsening, and stable CaCO3 formation. Results highlight a tradeoff between strength and sequestration, informing optimized geopolymer design for sustainable construction in mining environments, including potential use in tailings stabilization and mine infrastructure.