Evaluation of Palm Kernel Shell Ash and Rice Husk Ash as Stabilizing Agents for Lateritic Soils in Road Pavement Applications
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2026-04-07
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Abstract
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