Compaction and mechanical characteristics and stabilization mechanism of carbonated reactive MgO-stabilized silt

The reinforcement technology of carbonation based on reactive magnesia (MgO) and carbon dioxide (CO 2 ) is a low-carbon and high-efficiency foundation treatment method. This paper investigates the compaction, mechanical and microstructural characteristics of carbonated reactive MgO-stabilized silt with varying MgO-soil ratios, carbonation time and water-soil ratios. The results indicate that the maximum dry density of uncarbonated reactive MgO-stabilized silt increases while the optimum moisture content reduces compared to the parent soil. The unconfined compressive strength of reactive MgO-stabilized soil was found to have increased after CO 2 carbonation for several hours. With increasing MgO-soil ratio and carbonation time, the failure mode changes from elasticplastic to brittleness, and the failure strain of carbonated specimens mainly ranges between 0.8% and 1.6% and the ratio of the deformation modulus to unconfined compressive strength is about 30 to 200. The water-soil ratio has a slight influence on the evolution of strength. Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) analyses have indicated that the carbonation products facilitate the strength growth of reactive MgO-stabilized silt. Thermogravimetric analysis (TGA) shows that CO 2 uptake increases with increasing carbonation time and achieves the highest under the MgO-soil ratio of 20%, carbonation time of 6 h, and water-soil ratio of 25%. The stabilization mechanism of carbonated reactive MgO-stabilized silt is proposed according to microstructure analyses, providing a deeper understanding of the application of the reactive MgO carbonation technology in the ground reinforcement.