Geotechnical experimental study about the influence of RHA and SBA agricultural wastes on the engineering improvement of black cotton soils and cost-effectiveness: A case of railway performances in Shire Valley, Malawi

Abstract

Black cotton soil (BCS) improvement to provide stable railway structure foundations is one of the priorities of the Malawi country. BCS has initiated instability to railway structures in the Shire Valley, minimising their lifespan and leaving them non-operation. This necessitated the use of appropriate stabilization methods for the BCS. Several studies have been carried out to stabilise this soil. However, most of the studies adopt conventional admixtures such as lime and cement, which are someway expensive. This study aims to investigate the appropriateness of additives of the RHA and SBA agricultural waste materials for stabilizing BCS, in terms of the dry weight, UCS and CBR of the soils. The BCS was treated with RHA and SBA additives in percentages of 0, 4, 8, 12 and 16. The obtained laboratory experimental results showed that the additives of the RHA and SBA significantly improved the dry densities, compressive strength and penetration properties of the BCS. The study determined that up to 16% of both RHA and SBA can be used to stabilize the BCS for satisfactory engineering performance of railway structures in the Shire Valley. Moreover, the cost effectiveness of railway structures on the treated BCS with the RHA and SBA additives was analysed. The BCS stabilisation with the RHA and SBA was validated, and this research work gives a significant and practical reference on similar studies.