Utilization of Industrial Wastes in Pavements Laid over Expansive Clay Sub-Grades

Pavements founded in expansive soils undergo distress because of alternate swelling and shrinkage with respect to the changes in the moisture content. While variation in soil moisture content is inevitable over the life of a pavement, the performance of expansive sub-grades can be improved by adopting suitable measures. Cohesive non-swelling soil cushion is among the several techniques available to mitigate the problems associated with expansive clays. Since this technique has a few limitations, an alternative has been tried by providing a cushion of industrial waste, stabilized with lime. Granulated blast furnace slag and fly ash are the by-products of steel plants and thermal power plants respectively; whose disposal poses a problem. They can be used effectively as cushioning materials in place of sand or CNS. Detailed laboratory studies have been carried out, using these materials for cushioning over expansive clay beds. Lime-stabilized ground granulated blast furnace slag or fly ash, in the form of a cushion, has been placed over an expansive soil bed and the resulting heave measured. In both cases considerable reduction in heave was noticed in the expansive clay beds. CBR tests were also conducted on the cushion-soil system. Their results indicate a significant increase in the soaked CBR value. This investigation points to the utility of these two waste materials for use in sub-bases of flexible pavements.