Geotechnical properties of lateritic soil stabilized with rice husk ash and potassium carbonate for pavement construction

Rice Husk Ash (RHA) is a potential cementitious material with a high surface area. The high cost of cement and greenhouse gas emissions from its production necessitate exploring the use of agricultural residues. This study investigates the geotechnical properties of lateritic soil stabilized with RHA and potassium carbonate (potash) for highway pavement. Lateritic soil samples, rice husk, and potash were obtained from Aroje, Olojo, and Takkie, respectively, in Ogbomoso. Natural moisture content (NMC), plasticity index (PI), and percentage passing sieve number 20 were determined for natural lateritic soil using standard methods. Rice husk was washed, dried, calcinated at 600°C, ground, and sieved through sieve number 20. Oxide composition of silica, alumina, and iron oxide was determined using X-Ray Fluorescence. Lateritic soil was stabilized with varying proportions of RHA and potash. Liquid limit (LL), plastic limit (PL), optimum moisture content (OMC), maximum dry density (MDD), California bearing ratio (CBR), and unconfined compressive strength (UCS) were determined according to BS 1377. Effects of RHA and potash were analyzed using two-way ANOVA at a 95% significance level. The NMC, PI, and percentage passing sieve number 20 of natural soil were 10%, 50%, and 32.76%, respectively. RHA contained 82.10% silica, 1.21% alumina, and 1.30% iron oxide. For stabilized soil, LL, PL, PI, MDD, CBR, and UCS ranged 28.0-31.50%, 28.0-31.0%, 0.5-3.5%, 10-13.9 g/cm³, 78-99%, and 200-368 kPa, respectively. Two-way ANOVA revealed significant effects for MDD (p = 0.0024) and OMC (p = 0.00007), while PI and CBR showed non-significant results (p > 0.05). Stabilization with RHA and potash enhanced geotechnical properties, making the soil suitable for subgrade materials in road construction