Evaluating the Improvement of Expansive Soil Properties by Blending with Red Soils

One of the most abundant construction materials is soil; nevertheless, certain varieties provide serious engineering difficulties because of their low strength, low permeability, and rapid swell-shrink response to moisture changes. Through a variety of techniques, engineers have worked to increase the expansive soils' bearing capacity and shear strength over time. By mixing expansive soil with red soil, this study seeks to increase it’s the strength of expansive soil and make it more appropriate for construction. For laboratory testing, two types of expansive soil and three types of red soil-red-brownish, red gravel, and red fine soil were taken from Jimma Town. Combining expansive soil with red soil considerably enhanced its engineering properties, fulfilling design specifications for bearing capacity, plasticity, and compaction. Significant improvements were observed when red-brownish and red gravel soils were added at 15%, 30%, 45%, and 60%. As a result, the blended soil was deemed adequate for subgrade construction. The maximum dry density (MDD) increased from 1.40 g/cm³ to 1.62 g/cm³ and 1.61 g/cm³, respectively, while the California Bearing Ratio (CBR) increased from 2.75% to 17.79% and 17.62%. However, there were very few changes in CBR, index values, compaction characteristics, and free swell when red fine soil was mixed with expansive soil. The study's overall findings indicate that red-brownish and red gravel soils when combined with expansive soil greatly increase their qualities, but red fine soil just slightly improves them.