Experimental Study on Mechanical Properties of CO₂ Mineralization Sequestration in Blast Furnace Slag and Steel Slag Based Tailings Backfill

To synergistically achieve CO₂ sequestration and industrial solid waste resource utilization, this study proposes replacing 80% of cement with blast furnace slag powder and steel slag powder in cementitious systems, and incorporating iron tailings to prepare CO₂ mineralization backfill.By systematically testing the uniaxial compressive strength, phase composition, microstructure, and carbon sequestration rate of backfill materials before and after mineralization, this study investigates the mechanism by which solid waste blending ratios influence the mechanical properties and carbon sequestration effectiveness of backfill.The results indicate that the compressive strength of the backfill exhibits a linear decreasing trend as the proportion of blast furnace slag powder and steel slag powder decreases. When the mass ratio of blast furnace slag powder, steel slag powder, and cement is 2∶7∶1, the mineralized backfill demonstrates optimal mechanical properties, with uniaxial compressive strengths of 4.38, 5.63, and 6.65 MPa at 7, 14, and 28 days, respectively.Microstructural analysis reveals that at 28 days, SiO₂ within the backfill and the generated CaCO₃ jointly densified the internal pore structure, providing critical support for mechanical strength. However, as the steel slag powder content increased, the CaCO₃ in the mineralized products gradually transformed from rhombohedral to rod−like crystals. This shift weakened the interfacial bonding between different materials, leading to a loosening of the structure and consequently reducing compressive strength.The carbon fixation rate of the backfill specimens at different mass ratios ranged from 9.57% to 10.28%, with no significant difference. This phenomenon is directly related to the similar oxide content in each raw material.This study provides a novel technical pathway for tailings backfilling in green mines, offering significant engineering application value and theoretical reference for advancing the synergistic development of CO₂ geological sequestration and efficient utilization of industrial solid waste.