This study investigated the potential of cassava peel ash (CPA) as an environmentally friendly stabilizing material for enhancing the geotechnical properties of lateritic soil intended for pavement construction. Lateritic soil samples were treated with 0%, 2%, 4%, 6%, 8%, and 10% CPA and subjected to a series of laboratory tests to evaluate their engineering performance. The tests included Atterberg limits, compaction characteristics, and California Bearing Ratio (CBR) determinations. The untreated soil exhibited a liquid limit of 42%, plastic limit of 24%, plasticity index of 18%, maximum dry density (MDD) of 1.78 Mg/m³, optimum moisture content (OMC) of 13.5%, unsoaked CBR of 18%, and soaked CBR of 11%, indicating inadequate strength and considerable moisture sensitivity for direct use as pavement subgrade material. The addition of cassava peel ash produced noticeable improvements in the soil properties. Plasticity decreased considerably, with the liquid limit reducing to 34% and the plasticity index to 9.2%. Compaction characteristics also improved, as the MDD increased to 1.92 Mg/m³, while both soaked and unsoaked CBR values increased substantially, demonstrating enhanced load-bearing capacity and greater resistance to moisture damage. The optimum stabilization level was achieved at 6% CPA, which produced the highest dry density and CBR values. Further increases in CPA content resulted in slight reductions in performance, likely due to excess ash interfering with effective soil compaction. The findings indicate that cassava peel ash is a low-cost, sustainable, and effective stabilizing agent capable of improving the engineering performance of lateritic soils for pavement subgrade applications.

Keywords: Atterberg limits, California Bearing Ratio (CBR), Lateritic Soil, Maximum Dry Density (MDD), Moisture Content.