Cassava peel ash modified black cotton soil as material for hydraulic barriers in municipal solid waste containment facility

Abstract

This study investigates the potential of cassava peel ash (CPA) modified black cotton soil as a compacted clay barrier in a waste containment facility. Classification of the soil sample and chemical composition of cassava peel ash used were determined. Laboratory determination of some design parameters such as hydraulic conductivity, volumetric shrinkage and unconfined compressive strength of CPA-black cotton soil mixture were carried out using three compactive methods (Standard Proctor, SP, West African Standard, WAS and Modified Proctor, MP) at a stepped increment of 4% up to 24% CPA by dry weight of compacted soil prepared with water contents 2% dry of OMC, optimum moisture content (OMC), 2 and 4% wet of OMC. The cation exchange capacity (CEC) of the natural and treated specimens was determined via batch equilibrium adsorption test, and finally, the microstructure of optimally blended specimens was studied through scanning electron microscopy. The natural black cotton soil was grouped as A-7-6 (31) based on the AASHTO system and as CH (clay with high plasticity) using USCS. This study revealed that at 16% CPA and compacted within the range of 9.6-15.3% water content, black cotton soil–CPA blend compacted with not lower than Standard Proctor compaction energy fulfil design parameters requirements for its application as liner/cover in municipal waste repository facility. • Pozzolanic behaviour of CPA for the treatment of expansive soil was established. • Black cotton soil-CPA blend was found to be suitable as compacted barrier material in MSW landfill. • Landfill barrier parameters were fulfilled at 16% CPA by mass of dry soil when compacted at 9.6-15.3% water content.