Multi-scale experimental study on the waste soil co-solidified by CO2 and industrial waste

The feasibility of CO2–CCR–WZ01 co-curing of engineering residues was investigated through multi-scale tests, including micro-, elementary-, and model-scale experiments to enhance the efficiency of curing and resource utilization of engineering waste soil. Pure industrial waste slag (WZ01) was used as a curing agent, while calcium carbide residue (CCR) served as an alkaline activator, in combination with CO2 carbonation technology. Unconfined compressive strength tests and CO2 absorption rate tests were conducted to analyze the effects of four factors on the carbonation process: carbonation time (Tc), carbonation temperature (Kc), carbon pressure (Pc), and CO? concentration (Wc). The microscopic evolution of CO2–CCR–WZ01-stabilized soil was examined through microscopic and model tests to assess the effectiveness of the CO2–CCR–WZ01 co-curing technology. The results indicate optimal carbonation occurs when Tc = 6 h, Kc = 60 °C, Pc = 600 kPa, and Wc = 50%. The synergistic effect of the carbonation-curing reaction promotes the formation of products such as calcite, C–A–H, and C–S–H, which effectively fill the pores and enhance the strength of the residual soil. Under the influence of CO2–CCR–WZ01, the permeability index of the carbonized soil is significantly reduced, the bearing capacity reaches 700 kPa, and substantial improvements are observed in the basic physical properties of the soil. The CO2–CCR–WZ01 co-curing technology demonstrates high efficiency, low carbon emissions, and environmental sustainability, making it a promising solution for the resource utilization of engineering residues.