EFFECT OF SODIUM CARBONATE ON RICE HUSK ASH TO STABILIZE LATERITIC SOIL FOR USE IN ROAD CONSTRUCTION

Abstract

Lateritic soils commonly used in tropical road construction often exhibit high plasticity and inadequate strength, limiting their direct application in pavement layers.This study investigates the effectiveness of rice husk ash (RHA) activated with sodium carbonate (Na2CO3) as a sustainable stabilizing system for lateritic soil improvement.The materials were characterized for their chemical and mineralogical composition using X-ray fluorescence (XRF) and X-ray diffraction (XRD). The soil was treated with varying proportions of RHA (0–15%) and Na2CO3 (0–12%), and evaluated through Atterberg limits, compaction characteristics, California Bearing Ratio (CBR) under soaked and unsoaked conditions, unconfined compressive strength (UCS), and shear strength tests following relevant British Standards. A two-way ANOVA was employed to assess the statistical significance of the stabilizers’ effects. Results revealed that RHA is rich in reactive silica, while the lateritic soil is predominantly kaolinitic, enabling effective alkali-activated pozzolanic reactions. Stabilization significantly reduced plasticity and enhanced strength properties, with the optimum blend of 15% RHA and 12% Na2CO3 yielding the highest CBR, UCS, and shear strength values. Statistical analysis confirmed the significant influence of the stabilizers on key engineering properties. The study demonstrates that sodium carbonate–activated RHA is an effective and environmentally sustainable alternative for lateritic soil stabilization in pavement applications.