Compaction and strength characteristics of lead contaminated lateritic soil treated with eco-friendly biopolymer for use as road foundation material

Abstract

Reuse of unwanted soil material due to contamination is one of the available alternative to mitigate the depletion of natural construction material like lateritic soil. Lateritic soil can become contaminated as a result of mining activities. However, assessment of such soil for adequate compaction and strength development is a critical requirement for establishing foundation for road pavement failure of which can result in rapid deterioration of structural integrity of pavement. The research paper investigated the efficacy of Gum Arabic biopolymer (GAB) as eco-friendly additive, in enhancing strength development of lead-contaminated lateritic soil (LCLS) for use as foundation material for road pavement. Varying contents of GAB up to 25% of the dry weight of soil in 5% succession was used in treating LCLS. Compaction characteristics, Maximum Dry Density (MDD) and Optimal Moisture Content (OMC), and California Bearing Ratio (CBR) with microstructural analysis of the treated soil were assessed using three distinct compactive efforts: British Standard Light (BSL), West African Standard (WAS), and British Standard Heavy (BSH). With increase in GAB content, there is a corresponding rise in MDD, while OMC decreased across all three compaction efforts. Optimal CBR values were obtained at 10% GAB content across the three compactive efforts. The Scanning Electron Microscopic (SEM) analysis revealed modifications in the surface morphology occurring at the peripheries of clay particles. The R-squared (R2) values of the regression models derived from statistical analysis of all dependent variables revealed that GAB, MDD, OMC and CE (compactive effort) collectively exert considerable significant effect over CBR values. However, the ultimate strength values fall short of the recommended thresholds for sub-base stabilization. This suggests that a GAB content of 10% enhances the characteristics of contaminated lateritic soil. However, it should not be employed as a sole stabilizer; instead, it could be considered as a potential admixture in cement stabilization.