Role of amount and type of clay in the lime stabilization of soils

The effect of quantity of lime and duration of curing on the basic properties of a black cotton soil has been studied in this paper. The optimum lime content was found to be 6%. To investigate the role of clay content, black cotton soil containing different amounts of clay size fractions was also cured with 6% lime and the properties studied. To study the effect of type of clay mineral, commercially available kaolinite has also been mixed with 6% lime and the properties studied. Immediately on addition of lime, the liquid limit of black cotton soil decreases, but it increases with increase in duration of curing for any percentage of lime. These changes have been explained by changes in the thickness of the diffuse double layer and associated fabric changes. Studies on the changes in the properties of plastic limit, shrinkage limit and free swell index on lime addition help us to understand the controlling mechanisms. The effect of the double layer increases for montmorillonitic soils with increasing clay content, while fabric change controls the behaviour of black cotton soil with lesser clay content. The changes in properties of kaolinite are less pronounced than those in montmorillonitic clays on treatment with lime