Stabilization of Lateritic Soil from Iyamho (Edo State, Nigeria) with SP430 Superplasticizer: A Geotechnical Performance Study

Abstract

Lateritic soils, prevalent in tropical regions like Nigeria, are widely used in civil engineering applications such as road subgrades, embankments, and foundations due to their abundance and favorable natural properties. However, their variable geotechnical characteristics, influenced by local geological and hydrological conditions, necessitate site-specific studies to ensure reliable performance. This study investigates the geotechnical performance of lateritic soil from Iyamho, Edo State, Nigeria, stabilised with SP430 superplasticiser, a sulphonated naphthalene formaldehyde-based admixture.

Five key geotechnical tests—specific gravity, sieve analysis, Atterberg limits, standard Proctor compaction, and California Bearing Ratio (CBR)—were conducted on both untreated and stabilized soil samples with SP430 dosages of 2.5%, 5.0%, and 7.5%, following British Standards (BS 1377 and BS 1924). The untreated soil exhibited a specific gravity of 2.55, indicative of iron-rich lateritic composition, and a well-graded particle size distribution with 48.56% fines, suggesting moderate plasticity and compaction potential.

Stabilization with SP430 increased specific gravity to 2.78 at 7.5% dosage, reduced the plasticity index from 5.19% to 1.30% at 5.0% dosage, and improved maximum dry density from 1.90 Mg/m³ to 1.95 Mg/m³ while lowering optimum moisture content from 13.25% to 10.26%. However, CBR values decreased to 2.05% at 2.5% SP430, then increased to 5.65% at 7.5%, remaining below the untreated value of 12.50% and the 30% threshold for high-traffic pavement applications. This indicates limited suitability as a standalone stabilizer without supplementary stabilization.

These findings suggest that SP430 enhances soil density, reduces plasticity, and improves compaction efficiency, but its efficacy for high-load applications is limited. The study provides a baseline for optimizing stabilization strategies for Iyamho lateritic soil, recommending combined use with pozzolanic materials for enhanced performance in demanding infrastructure projects.