GEOTECHNICAL ENHANCEMENT OF LATERITIC SOILS USING NANO-SILICA AND PLANTAIN PEEL ASH: PHYSICAL, COMPACTION, AND STRENGTH CHARACTERISTICS

Abstract

The geotechnical properties of lateritic soils from Ibienafe, South Ibie, Edo State, Nigeria, were assessed for pavement construction using both untreated and stabilized samples obtained from Locations A, B, and C. Due to similar geotechnical characteristics across sites, Location B was selected for stabilization. Laboratory analyses were performed in accordance with BS 1377: Parts 2 and 4 (1990), comprising specific gravity determination, particle size distribution, Atterberg limits, compaction characteristics, and California Bearing Ratio (CBR). Untreated soils, with a CBR of 36.35%, suited low-traffic subgrades but required stabilization. The results showed consistent specific gravity (2.54–2.56), fine-grained composition (84.36–85.13% passing 0.075 mm, classified as lean clay, CL), moderate plasticity (PI 11.58–12.02%), and compaction (MDD 1.85–1.90 g/cm³, OMC 11.03–14.16%). Stabilization with 2.5% and 5.0% Plantain Peel Ash (PPA) reduced CBR (31.05–34.09%), compaction (MDD 1.82–1.83 g/cm³, OMC 15.39–18.54%), and specific gravity (2.45), indicating limited benefits. Conversely, 2.5% and 5.0% Nano-Silica (NS) improved CBR (36.21–39.47%), reduced plasticity (PI 4.71–6.61%), and increased density (Gs 2.53–2.60). The 5.0% PPA and 2.5% NS combination yielded the highest CBR (48.55%), optimal compaction (MDD 1.79 g/cm³, OMC 18.13%), and low plasticity (PI 6.73%), ideal for subbase in light-traffic roads, highlighting NS’s superior stabilization and PPA-NS eco-efficiency.