The freezing-thawing (F-T) durability of reactive MgO-admixed silty clay subjected to the forced carbonation has not been deeply understood despite the satisfactory engineering performance. A set of physical and mechanical tests as well as micro analyses were conducted to explore the engineering and microstructural features of MgO‑carbonated silty clay after the cyclical F-T. The research outcomes indicated that the weight change rates of MgO‑carbonated silty clay showed a fluctuating change under the increasing F-T cycle, but the water content, density and dry density almost remained stable. The strengths, deformation moduli and durability indexes of MgO‑carbonated specimens decreased by ~0.8 MPa, ~100 MPa and 0.17 respectively after 2–8 F-T cycles. Nevertheless, the strengths were still more than twice as high as those of Portland cement (PC)-solidified specimens. The repeated F-T cycles had almost no influence on the carbonation products and crystalline morphologies of MgO‑carbonated silty clay, but the dense aggregates were divided into loose fragments. The cumulative pore volumes of MgO‑carbonated samples had some increase of about 0.015 mL/g after the F-T exposure, and the pore-volume distribution turned into a three-peak curve after ten F-T cycles. Besides, the volumes of the total pore, macro pore and large pore had great increase after F-T cycles, while the volumes of other pores decreased. These findings showed a relatively good F-T durability of MgO‑carbonated silty clay, and would be beneficial for facilitating the application of MgO carbonation in the soil improvement of cold regions.

尽管具有令人满意的工程性能，但反应性 MgO 混合粉质粘土经受强制碳酸化后的冻融 (FT) 耐久性尚未得到深入了解。进行了一系列物理和机械测试以及微观分析，以探索循环 FT 后 MgO 碳酸化粉质粘土的工程和微观结构特征。研究结果表明，随着FT循环次数的增加，MgO-碳酸化粉质粘土的重量变化率呈现波动变化，但含水量、密度和干密度几乎保持稳定。经过 2-8 次 FT 循环后，MgO 碳化试样的强度、变形模量和耐久性指数分别下降了~0.8 MPa、~100 MPa 和 0.17。尽管如此，强度仍然是波特兰水泥 (PC) 固化试样的两倍多。重复的 FT 循环对 MgO 碳酸化粉质粘土的碳酸化产物和结晶形态几乎没有影响，但致密的聚集体被分成松散的碎片。FT暴露后MgO-carbonated样品的累积孔体积有一些增加约0.015 mL / g，并且在10个FT循环后孔体积分布变成三峰曲线。此外，FT循环后总孔、大孔和大孔的体积都有很大的增加，而其他孔的体积则减少。这些发现表明MgO-碳酸化粉质粘土具有较好的FT耐久性，有利于促进MgO碳酸化在寒冷地区土壤改良中的应用。