Evaluation of Palm Kernel Shell Ash and Rice Husk Ash as Stabilizing Agents for Lateritic Soils in Road Pavement Applications

This empirical investigation evaluates the geotechnical modifications induced by integrating rice husk ash alongside palm kernel shell ash into lateritic earth. Subsurface materials were excavated from a depth of one meter along Iraa Road in Offa, Kwara State, Nigeria, following the careful stripping of the organic top layer to ensure sample purity. A rigorous suite of laboratory assessments was deployed to determine how specific dosages of these agro-wastes alter the foundational California Bearing Ratio (CBR), Maximum Dry Density (MDD), and Optimum Moisture Content (OMC). In its pristine state, the sampled earth yielded a CBR of 27%, denoting a subgrade of merely passable quality. However, introducing a binder matrix composed of 2% rice husk ash and 4% palm kernel shell ash propelled the CBR up to 41%, translating to a formidable upgrade in structural load endurance. Concurrently, the moisture demand (OMC) shifted upwards from 12.60% to 16.10%, while the dry density (MDD) saw a marginal but vital enhancement from 1.67 kg/m³ to 1.72 kg/m³, a shift indicative of superior particle amalgamation and compaction mechanics. Notably, escalating the binder concentrations beyond this precise threshold triggered a deterioration in the geotechnical indices, proving that an optimal saturation point exists, beyond which additional ash impairs structural cohesion. Ultimately, these laboratory outcomes validate that a meticulously calibrated blend of these two ashes fundamentally upgrades the mechanical limits of lateritic soils. Utilizing these specific byproducts delivers an ecologically sound, financially viable methodology for reinforcing pavement subgrades while simultaneously mitigating massive agricultural waste burdens.