A Study on Subgrade Soil Treated With Cattle Bone Ash and Wheat Husk Ash: In Cae of Ali-Agarfa Wabe Road Project, South East Ethiopia

Abstract

The soils that cause effective damages to the pavement structures are expansive soil. These damages occur due to poor or unfavorited engineering properties, such as low bearing capacity, high liquid limit, high compressibility, high volume changes, etc. The roads on this type of subgrade soil fail before their expect design life. To minimize damage and overall costs, it is essential to improve the strength properties of such soils through the use of soil stabilization methods. In this study, alternative local waste materials, cattle bone ash (CBA) and wheat husk ash (WHA), were used as additives to help improve the properties of expansive soil from Bale Agarfa. The weakest soil samples were selected based on their plasticity, swelling properties, CBR, and compressive strength. The research also evaluated the effects of blending CBA and WHA at various percentages (2.5%, 5%, 7.5%, and 10%) on the soil's index and engineering properties, such as Atterberg limits, linear shrinkage, free swelling, compaction, CBR, and unconfined compressive strength. The results showed a decrease in liquid limit, plastic index, free swelling index (FSI), free swell ratio (FSR), and linear shrinkage when CBA and WHA were blended up to 7.5%. Conversely, maximum dry density, CBR, and UCS increased with the addition of both CBA and WHA. Based on the overall test results, the optimum ratio of the blended CBA and WHA for improving expansive soil in this study was proposed to be 7.5%.