GEOTECHNICAL PROPERTIES OF LATERITIC SOIL – BENTONITE MIXTURE TREATED WITH BAMBOO LEAF ASH

Abstract

The study investigated the geotechnical properties of lateritic soil-bentonite mixtures treated with bamboo leaf ash. Sodium bentonite was used for the study and was added to lateritic soil in an increasing order of 5%, 10%, 15% and 20% by weight of lateritic soil. The mixture (laterite + bentonite) was treated with bamboo leaf ash. Bamboo leaf ash was added to lateritic soilbentonite mixtures in an increasing order of 4%, 8%, 12% and 16% by weight of lateritic soil. The mixtures were subjected to geotechnical testing. The tests include: sieve analysis test, specific gravity test, compaction test, Atterberg limits (liquid and plastic) test, UCS test, hydraulic conductivity test and volumetric shrinkage test. Results obtained from sieve analysis test revealed that the lateritic soil was classified as A-7-6 according to AASHTO Soil Classification System and CH (clay of high plasticity) according to Unified Soil Classification System. The specific gravity of lateritic soil increased on addition of bentonite while for lateritic soil-bentonite mixtures treated with bamboo leaf ash the specific gravity was found to decrease. Volumetric shrinkage strain test was conducted after drying for 5 days, the VSS increased with higher compaction water content. The maximum dry unit weight of lateritic soil increased marginally on addition of bentonite to lateritic soil while for lateritic soil-bentonite mixtures treated with bamboo leaf ash, an increasing and decreasing trend in maximum dry unit weight was observed. The results showed improvement in the plasticity index (PI) and UCS values of the treated soil. The PI decreased from 30.58% to 19.62% and UCS values increased from 103.86kN/m2 to 245.15kN/m2 . Improvements observed in the strength properties of lateritic soilbentonite mixtures treated with bamboo leaf ash were above the minimum values specified for landfill liner construction materials. The study therefore recommends the use of lateritic soilbentonite mixtures treated with bamboo leaf ash for use as material in the construction of landfill liners.