SUBGRADE STABILIZATION USING LIME AND BAGGASE ASH

Abstract

Pavement subgrade transfers the load from upper layers to ground, it works as foundation for highways. In regions of high rainfall, pavement subgrade with poor drainage loses load carrying capacity which results in pavement failure. Cementing agents including industrial and agricultural by-products are usually used to stabilize subgrade. Lime with bagasse ash is used to enhance the performance of subgrade. Bagasse ash is produced as a by-product of sugar industry. It is a pozzolonic material as it contains silica and alumina contents. Soil is attained from Islamabad-Murree-Muzafrabad expressway near Shwala. Due to high rainfall and poor drainage conditions in Murree region, the roads of the area fail. Continuous maintenance of road is required in this region. To assess the performance of soil-lime-bagasse ash mix moisture-density, unconfined compressive strength and California bearing ratio (CBR) tests were carried out. The study shows considerable increase in unconfined compressive strength UCS and CBR value. Unconfined compressive strength of samples soaked for 24hrs increased 31.5 times (from 6.55psi to 207psi). California bearing ratio CBR of samples soaked for 96hrs increased 12.5 times (from 12% to 152%). UCS and CBR value increased with addition of bagasse ash up to 5% along with lime. Further increase of bagasse ash percentage results in decrease of CBR value and unconfined compressive strength. So 3% to 6% lime along with 5% bagasse ash is found optimum for stabilization of the soil. The swell potential was almost reduced to zero. The study also shows decrease in maximum dry density and increase in optimum moisture content.