A Study on the Effect of Bitumen Emulsion and Cement on the Strength of Gravelly Subgrade Soil

Soil serves as a foundational material in nearly all construction activities, particularly in road infrastructure, where the strength of the subgrade layer directly influences pavement performance and longevity. In many regions, especially rural or semi-urban areas, naturally available gravelly subgrade soils often lack sufficient strength to withstand increasing traffic loads and environmental stresses. This necessitates soil stabilization to improve load-bearing capacity and long-term durability. This experimental study investigates the combined effect of Medium Setting (MS) cationic bitumen emulsion and Ordinary Portland Cement (OPC) on enhancing the engineering properties of red lateritic gravel soil. The primary objective is to evaluate improvements in California Bearing Ratio (CBR) and Maximum Dry Density (MDD), key parameters that influence pavement design and cost-efficiency. Laboratory tests were conducted under four different material combinations to determine the most effective mix in terms of strength gain. A small percentage of cement was used along with 3% bitumen emulsion to assess their combined influence on compaction characteristics and subgrade performance under soaked and unsoaked conditions. The results indicate that the incorporation of bitumen emulsion and cement significantly improves CBR values and dry density, suggesting a viable and sustainable solution for low-cost rural and secondary road stabilization, especially in regions with weak or variable subgrade conditions.