Study on the effect of cinder ash as an auxiliary additive mineral in hydrated lime treatment for expansive sub-grade soil in road construction

Expansive soils pose significant challenges to road construction globally due to their tendency to expand and contract with changes in moisture content, leading to pavement failure. In the construction industry, finding an economical and cost-effective alternative to conventional road construction materials is crucial. The use of a natural cinder ash and hydrated lime mixture as reinforcement has proven to be effective in addressing this issue. Cinder ash, a readily available waste material in countries like Ethiopia, is adaptable and water-resistant, making it an ideal choice for reinforcing expansive soil. This article investigates the strength performance of a cinder ash and hydrated lime mixture as a reinforcement material for expansive soil. The study involves mixing 0%, 20%, 25%, 30%, and 35% of cinder ash with soil stabilized with 2–5% hydrated lime. Expansive soil samples are prepared according to the ASSHTO & ASTM method and tested for compressive strength, California bearing ratio, bulk density, and water absorption. The findings reveal a 448.62%, and 374% increase in compressive strength and California Bearing Ratio respectively for the specimen containing 5% hydrated lime and 35% cinder ash, cured for 28 days. The water absorption is minimized at 15.23% for the 5% hydrated lime and 35% cinder ash mixture; while the maximum density of the soil is observed at 1.774 kg/m3 for the optimal combination of 5% hydrated lime and 35% cinder ash mix. The study suggests that using 5% hydrated lime and 35% cinder ash content for the stabilization of expansive soil significantly enhances the strength characteristics of compressed stabilized soil.