Engineering Performance of a Ternary Stabilization System for Lateritic Road Subbase Construction in Tropical Nigeria
1,2Ibrahim, N. A., 1Osuolale, O. M. and 1Ige, J. A.
1Department of Civil Engineering, Ladoke Akintola University of Technology, Ogbomoso, Oyo State Nigeria.
2Works and Services Unit, The Federal Polytechnic Offa, Offa, Nigeria.
DOI: 10.36108/laujoces/6202.71.0111
Abstract
The inadequacy of natural lateritic soils for highway pavement subbase construction in tropical West Africa necessitates effective and affordable stabilization solutions. This study presents the first systematic investigation of a ternary waste-based stabilization system comprising Rice Husk Ash (RHA), Granulated Steel Slag (GSS), and Calcium Carbide Residue (CCR) to improve lateritic soil from Offa, Kwara State, Nigeria. Six mix proportions (Mixes A–F) were designed at incremental RHA:GSS:CCR ratios of 0:0:0, 3:2:2, 6:4:4, 9:6:6, 12:8:8, and 15:10:10 percent by dry mass of soil. The experimental program evaluated Atterberg limits, specific gravity, compaction characteristics (OMC and MDD), California Bearing Ratio (CBR), and Unconfined Compressive Strength (UCS) after 7 and 28 days of curing. The ternary system substantially improved the engineering properties of the lateritic soil. The Plasticity Index was reduced from 19% (natural laterite) to 10% at the optimum proportion (Mix F). The maximum dry density occurred in Mix B (1570.36 kg/m³) and generally decreased with increasing stabilizer content, reaching a minimum value of 1355.87 kg/m³ at Mix F.CBR peaked at Mix E (73.44%), representing a 13.7% improvement. In contrast, UCS peaked at Mix E (609.11 kPa), representing a 67.9% improvement, both substantially exceeding the Federal Ministry of Works and Housing (FMWH) minimum specifications of 30% and 200 kPa, respectively. Mix E is identified as the optimum formulation. The RHA-GSS-CCR ternary system offers a technically effective alternative for constructing lateritic road sub-bases in tropical environments.
Keywords: Lateritic Soil, Soil Stabilization, Stabilizers, Index Properties, Strength Properties.