Mechanical Properties and Durability of Lime–Metakaolin-Treated Saline Soil

This study investigated the effectiveness of lime–metakaolin for stabilizing saline soils, which are widely distributed in coastal areas and exhibit poor engineering properties. The effects of lime–metakaolin mixing ratio and age of maintenance on the mechanical properties of saline soils, and the effects of submergence age and the number of wet and dry cycles on the stability of saline soils, were systematically analyzed using indoor tests. The results demonstrated that the incorporation of metakaolin significantly improved lime-amended saline soil’s compressive and shear strength. When the NaCl content was 1.3% and the metakaolin dosage was 3.0%, the compressive strength of the amended soil increased by 84%, to 1.33 MPa, compared with that of the pure lime-amended soil. Additionally, the shear strength, cohesion (c), and internal friction angle (φ) increased significantly with higher metakaolin dosages. Shear strength, cohesion, and angle of internal friction increased by 51.6%, 21.7%, and 10.8%, respectively, when the salt content was 1.3% and the metakaolin content was 3% compared with 0% metakaolin content. Furthermore, the addition of metakaolin substantially enhanced the water stability of the cured saline soil. After 9 days of water immersion, the water stability coefficient of the metakaolin-treated soil was as much as 19% higher than that of the soil without metakaolin. The synergistic use of lime and metakaolin was effective in mitigating the strength loss of saline soils under dry–wet cycles. After 12 cycles, the strength of the metakaolin-treated specimens increased by 62% compared with that of the untreated specimens, indicating improved durability. This study demonstrates that lime–metakaolin costabilization can effectively improve the engineering performance of saline soils, providing a feasible technical solution for the construction of infrastructure on saline soils.