Sustainable Stabilization of Lateritic Soil Using Rice Husk Ash-derived Nano-silica: Effects on Index Properties and Compaction Characteristics

Abstract

The growing need for sustainable materials in geotechnical engineering has encouraged the use of agricultural waste-derived nanomaterials for soil improvement. This study investigated the potential of nano-silica synthesised from rice husk ash (RHA) to improve the index properties and compaction characteristics of lateritic soil. The nano-silica was produced through washing, controlled burning, acid treatment, filtration, drying, ball milling, and calcination at 700 °C. X-ray fluorescence and X-ray diffraction analyses showed that the synthesised nano-silica contained 94.18% SiO₂ and exhibited an amorphous structure. The natural lateritic soil was classified as CL under the Unified Soil Classification System and A-7-6 (10) according to AASHTO, with a liquid limit of 47.2% and a plasticity index of 18.7%. Different proportions of nano-silica were added to the soil, and the treated samples were subjected to Atterberg limits and compaction tests using different compactive efforts. The results showed that nano-silica reduced the plasticity of the lateritic soil, with the plasticity index decreasing from 18.7% to 6.7% at 2.5% nano-silica content. The highest maximum dry densities of 1.57, 1.64 and 1.78 Mg/m³ were obtained at 1.5% nano-silica for British Standard Light, West African Standard and British Standard Heavy compaction, respectively. The corresponding optimum moisture contents were 21.5%, 18.5% and 15.0%. Overall, the findings indicate that rice husk ash-derived nano-silica has good potential for modifying the plasticity and compaction behaviour of weak lateritic soil while providing a sustainable means of converting agricultural waste into a useful geotechnical material.