Index and Compaction Characteristics of Electrokinetically Remediated Crude Oil-Contaminated Lateritic Soil Using Different Electrode Materials

Crude oil contamination severely alters the index and compaction characteristics of lateritic soils, limiting their engineering reuse potential. Electrokinetic remediation (EKR) using different electrode materials offers a viable pathway to restore these properties; however, the electrode-specific influence on post-remediation index properties and compaction behaviour remains inadequately documented for Nigerian lateritic soils. Crude oil-contaminated lateritic soil was electrokinetically remediated over 20 days using graphite, carbon, and mild steel electrodes with sodium sulphate and SDS surfactant enhancement. Post-remediation index properties — specific gravity, particle size distribution, Atterberg limits — and compaction characteristics under British Standard Light (BSL), West African Standard (WAS), and British Standard Heavy (BSH) compactive efforts were determined following BS 1377 (1990). All remediated soils classified as lean clay (CL/A-7-6) with fines content 79.40–81.56%, liquid limits 41.91–45.78%, and plasticity indices 14.22–19.13%. Graphite produced the lowest PI (14.22%), reflecting superior hydrocarbon removal (73.34% TPH efficiency). Under BSL compaction, maximum dry density (MDD) ranged from 1.59–1.63 Mg/m³ with optimum moisture content (OMC) 25.23–29.71%. MDD consistently increased with compactive effort (BSL → WAS → BSH), while OMC decreased correspondingly. Graphite-treated soils exhibited the most stable plasticity and workability characteristics among the three electrode types. Conclusions: EKR effectively restores the index and compaction characteristics of crude oil-contaminated lateritic soil to ranges suitable for geotechnical reuse. Electrode material significantly influences the degree of plasticity reduction and densification achievable, with graphite demonstrating the most favourable overall index and compaction profile for engineered waste containment applications.