Cocoa pod and palm kernel shell ashes as partial replacement of portland cement in stabilizing laterites for road construction

Abstract

Cocoa pod and palm kernel shell ashes were evaluated as partial replacements of Portland cement for stabilization of lateritic soils with improved strength and reduced material cost in road construction. The iron, magnesium, sodium and potassium contents of the additives were similar to that of cement, but the calcium content of palm kernel shell ash was much lower. The lateritic soil used for road construction in the locality was unsuitable for sub-base and base course of roads unless stabilized, because of the high plasticity index and low California Bearing Ratio (CBR). Lateritic soil samples stabilized with cement-cocoa pod ash additive of 6 to 8 % or cement-palm kernel shell ash mixture of 2 to 8 % satisfied the requirements for use as road sub-base. Stabilized lateritic soils containing 6 – 8 % of either additive was suitable for base course in terms of CBR > 30 % for sub-base and 80 % for base course. The laterites exhibited plasticity indices < 12 % and liquid limits < 45 %, thereby conforming to UK Transport Research Laboratory and Nigerian Federal Ministry of Works Specifications for Roads and Bridges. The additives could serve as partial replacement of cement because of the strength and durability properties, and reduced cost of stabilized soils.