Improving the Mechanical Properties of Natural Soil Using Rice Husk Ash and Soy Bean Hull Ash in Biu – Borno State

Abstract

This study investigated the potential of rice husk ash (RHA) and soy bean hull ash (SBHA) as sustainable stabilizers for enhancing the mechanical properties of Biu soil in Borno State, Nigeria. Given the poor geotechnical characteristics of the native soil, the research explored the viability of these agro-waste pozzolans in improving the mechanical properties of the soil. A constant 20% pozzolanic replacement level was adopted across various mix proportions using a 1:4 cement-to-aggregate ratio. Laboratory tests were conducted on both untreated and treated soil samples using standardized methods. Results showed a consistent improvement in UCS and CBR values with varying proportions of RHA and SBHA, while PI values decreased accordingly, indicating reduced soil plasticity and improved stability. The highest UCS of 1400 kPa and CBR of 135% were recorded in BSC-04, while PI reduced to 16%, signifying enhanced load-bearing capacity and suitability for construction. These findings support the use of RHA and SBHA as effective, low-cost, and environmentally friendly alternatives for soil stabilization.