The effect of adding palm shell ash on soil shear strength

Abstract The soil in Tanjung Rejo Village, Percut Sei Tuan, Deli Serdang, is characterized by fine-grained clay with low stability. To enhance stability, this study focuses on soil stabilization using palm shell ash mixtures at varying percentages (0%, 4%, 6%, 8%, 10%, and 12%) under optimum moisture conditions. Stabilization involves mixing the clayey soil with additional materials to improve its technical properties, specifically employing palm kernel shell ash. Testing was conducted following ASTM methods. As the percentage of palm shell ash in the mixture increased, both cohesion and friction angle values showed an increasing trend, reaching optimal values at 10% palm shell ash. The Direct Shear test on native soil yielded the cohesion of 10.3 KPa and a shear angle of 14.6°, whereas the most optimum values for cohesion (14.1 KPa) and friction angle (24.60°) were observed in the soil mixture with 10% Palm Shell Ash (PSA). The palm shell ash mixture has good potential for use in road pavement, especially in Tanjung Rejo Village, Percut Sei Tuan, Deli Serdang, North Sumatra, Indonesia.