Geotechnical properties of lateritic soil stabilized with rice husk ash and potassium carbonate for pavement construction

Abstract

The production of Ordinary Portland Cement (OPC) is a significant source of CO? emissions, contributing approximately 7% of global CO? emissions. The high cost of OPC and the need for sustainable alternatives necessitate the exploration of waste materials like rice husk ash (RHA). This study investigates the effect of potassium carbonate as a chemical activator for RHA in stabilizing lateritic soil. Lateritic soil samples were collected from the Aroje, Ogbomoso, Nigeria, and stabilized with varying proportions of RHA and potassium carbonate. Standard laboratory tests including Atterberg limits, compaction, California Bearing Ratio (CBR), and Unconfined Compressive Strength (UCS) were conducted in accordance with BS 1377.Chemical and mineralogical analyses were performed using XRF, XRD, and SEM. Results showed that the optimal mix of 16% RHA and 4% potassium carbonate produced the most significant improvements in soil performance. The plasticity index reduced to 0.00%, indicating non-plastic behavior. The unsoaked CBR values increased from 16.3% to 71.8%. Similarly, the UCS improved from 96.5 kPa to 367.9 kPa. Maximum Dry Density (MDD) decreased from 1.87 g/cm³ to 1.75 g/cm³, while Optimum Moisture Content (OMC) increased from 13.2% to 18.6%.  XRF confirmed the high pozzolanic activity of RHA, with silica content exceeding 65%, and SEM images revealed a denser, cementitious matrix formation in the stabilized soil. In conclusion, the combination of rice husk ash and potassium carbonate significantly enhances the geotechnical properties of lateritic soil, making it an eco-friendly alternative to cement for road construction.