Freezing-thawing performance of reactive MgO-admixed silty clay subjected to forced carbonation

Abstract

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.