Effect of High-Volume Class F Fly Ash and Nano Lime on the Swelling Behavior and Microstructure of Expansive Soil

A balance between stabilization of expansive soil and taking care of sustainability issues has been a major challenge. The Indian environmental challenge is the large quantities of ash produced by thermal power plants, which are being disposed of. Using this fly ash as a stabilizer material is an environmentally friendly choice, which minimizes traditional soil replacement and economic construction. Over the past years, nanomaterials have presented a great potential in soil stabilization. This research paper examines the compound application of class F fly ash and nano lime in enhancing expansive clay located in Rajkot city. A synthesis of nano lime was done using a thermal decomposition procedure, and fly ash was obtained commercially. The fly ash was replaced with soil samples at a rate of 40%, 60%, and 80% by dry weight, and nano lime was added to the soil at 0.5% and 1.0% by dry weight. Geotechnical tests like Atterberg limits, Free Swell index and Swell pressure were performed, and microstructural analysis was carried out. The findings reveal that the swelling behavior of expansive soil significantly improves with increased dosages of fly ash and nano lime used in combination. The most effective performance was achieved with a mixture of 80% fly ash and 1% nano lime, leading to substantial reductions in plasticity and swell pressure and a marked improvement in shrinkage resistance. This combined stabilization strategy offers a sustainable and locally suitable solution for managing problematic soils in regions like Rajkot.