Effect of Compactive Efforts on Hydraulic Conductivity of Black Cotton Soil Treated with Cassava Peel Ash

Abstract

This paper presents the results of laboratory investigation carried out on the effect of compactive efforts on the hydraulic conductivity of black cotton soil treated with Cassava Peel Ash (CPA) at 0, 4, 8, 12, 16, 20 and 24% CPA treatment. Index properties, hydraulic conductivity and cation exchange capacity tests were carried out. Specimens were prepared at moulding water contents 2% dry, OMC, 2% wet and 4% wet of optimum moisture content using British Standard Light (BSL), British Standard Heavy (BSH) and West African Standard (WAS) compactive efforts. The results show that hydraulic conductivity value generally decreases as the CPA concentration is increased in the blend. At optimal 16% CPA treatment level, hydraulic conductivity values are 1.74 x 10-8, 1.40 x 10-8 and 8.42 x 10-9 cm/s for BSL, WAS and BSH energy levels. Cation exchange capacity (CEC) test was also conducted to further investigate the water holding capacity of the natural and treated specimens; the CEC indicates that CPA had positive contribution on the hydraulic conductivity of the treated specimens especially as CPA content is increased. This study revealed that hydraulic conductivity decreases to its minimum at higher compactive effort.