A Comparative Study of the Basic Strength and Hydraulic Properties of Lateritic Soils Stabilized with Rice Husk Ash and Bagasse Ash

Abstract

The strength and hydraulic properties of lateritic soils stabilized with bagasse ash (BA) and rice husk ash (RHA) were examined in this study. The three lateritic soil samples used in the study were obtained from a borrow pit near the main waste dumpsite in Ado Ekiti, Nigeria. The BA and RHA were obtained locally from the burning of fibrous residue of sugar cane and rice husk respectively. Classification of the soils using AASTHO indicates Soil 1 to be Group A-6 soil, Soil 2 to be Group A-2-6 soil and Soil 3 to be Group A-2-7 soil. In general, the optimum moisture content of the stabilized soils increased with increased content of the admixtures-BA and RHA. The maximum dry density of the stabilized soils decreased with increase in the quantity of BA and RHA. Likewise, the saturated hydraulic conductivity of the stabilized soils decreased slightly with increased content of BA and RHA. The values of the minimum hydraulic conductivity of the stabilized soils were of the order of 10-4cm/s, which are higher than the minimum requirement of 10-7cm/s for soil liners in municipal solid waste landfills. The low pozzolanic characteristics of BA and RHA in the stabilized soils were attributed to the low content of CaO needed to produce CaOH2, which is normally needed to produce pozzolanic reaction products in the presence of water. The characteristics of the modified soils appeared to be influenced by the change in the soil matrix following mixing. Comparison of individual behaviour of BA and RHA in each stabilized soil showed very similar characteristics. It was concluded that another modifier such as cement that has a high content of CaO should be added to the stabilized soils for the full pozzolanic potentials of BA and RHA to be realised.