OPTIMUM FLYASH TO INCREASE THE STRENGTH OF SUBGRADE

Abstract

Stabilization of problematic soils with fly ash not only improves engineering properties of soil but also provides a solution to challenges of fly ash disposal. Approximately 52,000 tons of fly ash produced annually at Boropukuria coal-based power plant in Bangladesh require a huge disposal area and create environmental problems. This paper reports the results of laboratory investigation carried out on expansive soil collected from Rajendrapur area stabilized with fly ash in varying percentages. Here, 4% cement is used as an activator. The effect of cement with varying fly ash contents are correlated with soaked California bearing ratio (CBR) value, swelling index and Atterberg limits of stabilized soil. The study finds that soaked CBR value of the soil improves from 1.73% to 26.07% after adding 6% of fly ash for 14 days of curing. With increasing of more fly ash content, strength decreases. So optimum value of fly ash content is 6% for which highest strength is obtained. Moreover, swelling index of the collected soil with 4-days soaking condition is found to be decreased by 47% when 6% fly ash is added. The outcome of this study will guide road engineers of Bangladesh to use fly ash as a stabilizing agent to improve the properties of subgrade