Research on the Thermal Conductivity and Microstructure of Calcium Lignosulfonate-Magnesium Oxide Solidified Loess

Loess, characterized by high porosity, a loose structure, and weak cementation, is highly prone to deformation and cracking under thermal stress, which significantly affects the bearing capacity of foundations and the stability of underground engineering structures. This study introduces an innovative approach that utilizes the eco-friendly modifier calcium lignosulfonate (CL) in combination with magnesium oxide (MgO) for the carbonation solidification treatment of loess. The research systematically investigated the thermal conductivity and underlying micro-mechanisms of the treated soil. A series of tests, including analyses of basic physical properties, measurements of thermal conductivity, X-ray diffraction (XRD), and scanning electron microscopy (SEM), were conducted to evaluate the effects of CL dosage, freeze–thaw cycles, moisture content, and dry density on the thermal conductivity of carbonation-solidified loess. The results indicate that carbonated solidified loess absorbed approximately 6% of CO2, while effectively reducing its collapsibility grade to a slightly collapsible classification. Additionally, its thermal conductivity decreased by 16.7%, thereby mitigating the influence of various environmental factors. Based on the experimental results, a microscopic mechanism model was developed. This study presents a sustainable and innovative technical solution for stabilizing loess foundations in cold regions.