Recently, the demand for rapid and cost-effective infrastructure development has led to the has led to the development of various soil improvement techniques, including stabilization. Studies on the incorporation of mineral materials such as lime and coal ash into soil stabilization have been carried out in several countries, and these studies have shown promising results. Given the beneficial properties or properties of coal ash, together with its availability and cost-effectiveness, the combination of coal ash with lime for clay soil stabilization is a viable option. This study evaluates lime and coal ash on the behavior and geotechnical properties of clay soils. The evaluation includes plasticity index (PI), compaction, uniaxial compressive strength, California bearing ratio (CBR) and direct shear tests, and direct shear tests. To achieve this, the process began with the mixing of clay with varying percentages of hydrated lime (4%, 6% and 7%), followed by a 28-day curing period for the samples. Coal ash was then added at different (5%, 15%, 25% and 50%) was incorporated into the clay and also cured for 28 days. In the final stage, the optimum amount of hydrated lime was determined, an amount of hydrated lime, equivalent to the amount of coal ash used, was added to the clay and the mixture was cured for a further 28 days. The results indicate that A mixture of 7% hydrated lime and 50% coal ash, after 28 days of curing, is an optimum combination for stabilizing the clay in the study area. This combination increased the uniaxial compressive strength by 1.87 times, the shear strength by 1.34 times and the CBR value by 6.4 times, making it suitable for use in the for use in the construction of pavement layers.
