Assessment of Volumentric Shrinkage and Hydraulic Conductivity of Lateritic Soil – Corn Cob Ash Admixure as Liner Materials

Abstract

A lateritic soil was treated with an agro-industrial waste—Corn Cob Ash (CCA)—using the West African Standard (WAS) compaction energy, with CCA content varied up to 12% in 3% increments. The test specimens were prepared at -4, -2, 0, 2, and 4% of optimum moisture content (OMC), extruded from the compaction mould, air-dried in the laboratory until no significant volume change was observed, and then tested for permeability using a falling head permeameter. The effects of CCA on the soil-CCA mixtures were assessed in terms of volumetric shrinkage and hydraulic conductivity. Results show that volumetric shrinkage decreased with increasing CCA content, reaching a minimum at 6% CCA, while hydraulic conductivity was lowest at 9% CCA,after which permeability slightly increased. Additionally, moulding water content significantly influenced volumetric shrinkage and hydraulic conductivity, as specimens compacted below OMC exhibited higher shrinkage and permeability, while those compacted above OMC initially showed lower shrinkage but increased void ratios, leading to higher permeability upon drying. These results indicate that not more than 6% and 9% CCA are optimal for reducing volumetric shrinkage and hydraulic conductivity, respectively. The findings suggest that CCA can be used as a sustainable stabilizer in soil modification for waste containment barrier materials.