The carbonation of cementitious materials with CO2 2 was utilised to prepare fluid solidified soil, and the characteristics of fluid solidified soil were investigated. Experimental tools such as flow extensibility, unconfined compressive strength, thermogravimetric analysis, and scanning electron microscopy were employed to explore the influence laws of different carbon dioxide pressures, cement dosages, and initial water contents on the strength properties and microstructural evolution of fluid consolidated soils. The results showed that with the increase of CO2 2 pressure, the flow characteristics of carbonated fluid solidified soil decreased and the unconfined compressive strength increased. This is due to the fact that after the carbonation process, the formation of carbonation products such as calcium carbonate and hydration products in the fluid solidified soil significantly improves the microstructure of the soil, which is the main reason for the increase in its strength. In addition, the carbonation test revealed that the ratio of the amount of COQ generated to the mass of cement was as high as 18.36 % under the condition of COQ pressure up to 0.20 MPa, which fully proved the high efficiency of the carbonation technology. Therefore, the carbonation technology has great potential and broad application prospects in optimising the performance of fluid solidified soil as well as achieving effective carbon sequestration.

To address the challenges posed by the significant quantity of ammonia-alkali white mud, this study explores the preparation of fluid solidified soil using ammonia-alkali white mud, mineral powder, and fly ash. The findings reveal that ammonia-alkali white mud primarily comprises sulfate, carbonate, and soluble chloride salt, with an alkaline solution and a well-developed pore structure. Optimal fluid solidified soil formulation, comprising 30% white mud, 30% salt mud, 25% mineral powder, 10% fly ash, and 5% calcium oxide, yields a slurry fluidity of 176 mm and a compressive strength of 3.98 MPa at 28 days. Microscopic analysis highlights AFt and C-S-H gel as the principal hydration products of fluid solidified soil. The fine particles of calcium carbonate in ammonia-alkali white mud fill the structural pores and intertwine with the hydration products, facilitating the formation of a dense structure, which constitutes the primary source of strength in fluid solidified soil. Furthermore, the heavy metal content of the solidified soil aligns with the first type of land use requirements outlined in the GB 36600-2018 standard, and the toxicity of the leaching solution adheres to the emission concentration limit stipulated by GB 8978-1996.