Model investigation of the low-carbon MgO-treated soil foundation based on CO₂ overall carbonation

The overall carbonation of MgO-admixed soil provides not only an efficient and environmentally friendly technique for improving soft ground but also a permanently safe solution for CO₂ sequestration. To evaluate the carbon sequestration potential and promote the carbonation application in soil improvement, a laboratory-scale model investigation is designed under pressurized carbonation considering the influences of MgO dosage and CO₂ ventilation mode (way). The temperature, dynamic resilience modulus, and dynamic cone penetration (DCP) were tested to assess the carbonation treatment effect. The physical, strength, and microscopic tests were also undertaken to reveal the evolution mechanisms of CO₂ migration in the MgO-carbonated foundation. The results indicate that the temperature peaks of MgO-treated foundation emerge at ∼20 h during hydration, but occur at a distance of 0–25 cm from the gas source within 6 h during carbonation. The dynamic resilience moduli of the model foundation increase by more than two times after carbonation and the DCP indices reduce dramatically. As the distance from the gas inlet increases, the bearing capacity, strength, and carbon sequestration decrease, whereas the moisture content increases. Compared to the end ventilation, the middle ventilation produces a higher carbonation degree and a wider carbonation area. The cementation and filling of nesquehonite and dypingite/hydromagnesite are verified to be critical factors for carbonation evolution and enhancing mechanical performances. Finally, the overall carbonation model is described schematically in three stages of CO₂ migration. The outcomes would help to facilitate the practical application of CO₂ sequestration in soil treatment.