This study investigates the potential for enhancing the geotechnical performance of sabkha soil from Ain M’Lila (Algeria) through cement-lime stabilization, with optimization of stabilizer dosages conducted using Response Surface Methodology (RSM). Twelve mixtures with varying contents of soil (90–100%), lime (0–10%), and cement (0–10%) were evaluated using a central composite design. Experimental testing included Proctor compaction, unconfined compressive strength (UCS), direct shear, California Bearing Ratio (CBR), and electrical conductivity (Ec), with data interpreted via ANOVA and RSM modeling. The untreated sabkha soil displayed unfavorable properties, such as 60% fines, an electrical conductivity of 16.33 mS/cm, 3585 mg/L of chlorides, and 4704 mg/L of sulfates. Nevertheless, RSM identified an optimal formulation comprising 6% cement and 4% lime, which led to remarkable improvements: UCS increased by 1007% (1583 kPa at 90 days), the CBR index rose by 442.89% (83.83), cohesion reached 38.2 kPa, and the pH stabilized at a highly alkaline value of 12.3, promoting pozzolanic activity. ANOVA results confirmed the significance of the models (p < 0.05), with strong coefficients of determination (R² values of 87.13%, 91.39%, 90.85%, 80.47%, and 89.03%) corresponding to maximum dry density, cohesion, internal friction angle, CBR, and UCS, respectively. Overall, the findings confirm that cement-lime treatment can effectively convert problematic sabkha soil into a reliable subgrade material for road infrastructure. Moreover, the RSM-based optimization approach provides a cost-effective and technically sound solution for soil stabilization in arid and semi-arid environments.

The sabkha soils of the Aïn M’lila region present major geotechnical challenges, including high salinity, significant gypsum and soluble salt contents, and low mechanical strength. To improve their geotechnical performance, this study evaluated the effectiveness of cement–lime stabilization at various mixing ratios. Mechanical tests, including compressibility, California bearing ratio (CBR), and unconfined compressive strength (UCS), were conducted to identify the optimal dosage. The 6/4% cement–lime mixture exhibited the best performance, showing a significant increase in bearing capacity and soil cohesion. Based on these results, an X-ray diffraction (XRD) analysis was carried out exclusively on this optimal mixture to examine the associated mineralogical transformations. The XRD results revealed a pronounced structural reorganization characterized by the formation of secondary carbonates and pozzolanic products (C-S-H and C-A-H), which contributed to matrix densification and improved mechanical resistance. Despite the persistence of certain evaporitic phases such as gypsum and halite, the 6/4% cement–lime mixture proved to be the most effective, confirming the suitability of this approach for the sustainable stabilization of sabkha soils.