Mechanical performance, energy dissipation, and failure mode evolution of CO2 mineralized cement paste backfill incorporating mine tailings

Mining industry generates ∼13 billion tons of tailings annually while contributing nearly 10% of global emissions, demanding integrated strategies for waste management. Mineralized cemented paste backfill (CPB) offers dual-function solution for structural ground support and in-situ carbon sequestration; however, effects of CO 2 injection on failure mechanics, energy dissipation, microstructural evolution, and carbon sequestration efficiency remain insufficiently understood. This study establishes the kinetic carbonation window for mineralized tailing-based cement paste backfill (MTCPB) by investigating CO 2 injection duration (0-20 min) and curing age (3, 7, 14 days) on mechanical performance, failure mode evolution, energy dissipation, and carbon sequestration capacity using uniaxial compressive strength (UCS), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), thermogravimetric analysis with differential scanning calorimetry (TGA-DSC), and Fourier-transform infrared spectroscopy (FTIR). An optimal 10-min CO 2 injection duration under these specific conditions elevated UCS from 2.10 to 2.54 MPa, energy absorption from 3.53 to 5.47 MJ/m 3 (54.9%), transforming failure mode from shear-dominated to tensile splitting, a structural safety outcome of greater significance than peak strength alone. Portlandite content decreased from 2.45% (control) to 1.18% (optimal), confirming substantial Ca(OH) 2 consumption, while carbonate content increased from 4.64% to 5.25%, with peak CO 2 uptake of 6.32%. Beyond optimal window, overcarbonation triggered surface passivation and matrix heterogeneity, reducing elastic modulus by 55% without measurable mineralogical benefit. FTIR confirmed Ca(OH) 2 depletion and CO 2 -driven ettringite-to-gypsum transformation. These findings advance backfill design toward performance-based paradigm integrating failure-mode control, microstructural optimization, and sustainable co-disposal of mine tailings and waste CO 2 , offering scalable, evidence-based foundation for carbon-negative underground backfilling.