Stabilization Of Expansive Soil Using Fly Ash

Abstract: Expansive soil is a major problem in civil engineering because its volume changes with changes in moisture content. Black cotton soil, which is commonly found in many parts of India, expands during the rainy season and shrinks during the dry season. This behaviour can cause cracks, uneven settlement and damage to roads and foundations. The present research work investigates the stabilization of expansive soil using fly ash as a waste-based stabilizing material. In this study, expansive soil collected from Kalmeshwar, Nagpur, Maharashtra, is mixed with fly ash obtained from Koradi Thermal Power Station, Nagpur. Fly ash is added in different proportions of 5%, 10%, 15% and 20% by dry weight of soil. The untreated soil is used as the control sample. Laboratory tests are carried out to study the changes in Liquid Limit, Plastic Limit, Plasticity Index, Free Swell Index, Optimum Moisture Content, Maximum Dry Density, California Bearing Ratio and Unconfined Compressive Strength. The results show that the addition of fly ash reduces the plasticity and swelling behaviour of expansive soil and improves its compaction and strength characteristics. Based on the considered experimental values, the 15% fly ash mixture gives better overall improvement in CBR and UCS, while higher fly ash content gives further reduction in plasticity and free swelling. The study indicates that fly ash can be effectively used to improve the engineering performance of expansive soil. Its use also provides a useful method for utilizing industrial waste and reducing the requirement for conventional stabilizing materials. The developed treatment can be considered for economical and sustainable pavement subgrade applications.