Effect of Lime and Fly Ash on Cation Exchange Capacity (CEC) and Unconfined Compressive Strength (UCS) of Soils

Abstract

The utilization of fly ash in India varies between 50-60% and the rest are disposed in ash ponds. The fly ash which are utilized for reclamation of low lying areas or which are used in geotechnical engineering application has the tendency of leaching the heavy metal pollutants and thus polluting the groundwater, surface water and surrounding soil. Also the discharge of effluents from waste water treatment plants may lead to pollution of the ground water. If these ground water pollution can be controlled by increasing the Cation Exchange Capacity of the sub soil through application of any of the additives such as lime, fly ash, cement etc. which also leads to increase in strength of the soil then that additive would be favourable in case of geotechnical projects where ground water pollution is of great concern. The present work aims to find the effect of additives namely Lime and Fly ash on Cation Exchange Capacity (CEC),Compaction characteristics, and Unconfined Compressive Strength (UCS) of two soils. The two soils used in this study are Sandy Clay (SC) and Low Plasticity Clay (CL).First the soils were mixed individually with varying contents of lime and fly ash to find out their effects on Cation Exchange Capacity (CEC) and for conducting Light compaction test to find the compaction characteristics. Then the treated soil samples compacted at Optimum Moisture Content (OMC) and Maximum Dry Density (MDD) were tested for Unconfined Compressive Strength (UCS) at different Curing periods. From the experimental results obtained, it is observed that for both soils, Cation Exchange Capacity (CEC) decreases more with increase in fly ash content than with Lime content. Also Optimum Moisture Content (OMC) increases and Maximum Dry density (MDD) decreases with increase in Lime and Fly ash content for both the soil samples. The Unconfined Compressive Strength (UCS) increases with lime and fly ash content up to a certain limit beyond which further increase in lime and fly ash content does not increase the Unconfined Compressive Strength (UCS) The Unconfined Compressive Strength (UCS) increases more with increase in Lime content than by increase in fly ash content. The Unconfined Compressive Strength (UCS) increases with curing time.