Laboratory Study on Natural Fiber Amended Fly Ash as an Expansive Soil Stabilizer

Abstract

Expansive soil subgrade pose major problems for the pavements due to their volume change characteristics. In the present investigation, the suitability of fibre reinforced fly ash on the stabilisation of expansive soil is studied. Coconut fibre is chosen as natural reinforcing fibre with a cut length of 10 mm and used in different percentages such as 0.25, 0.5 and 1% along with fly ash content of 20% of dry weight of soil. Laboratory tests includes standard Proctor tests, swelling pressure tests and California Bearing Ratio (CBR) tests were conducted to determine the maximum dry density (MDD), optimum moisture content (OMC), swelling pressure and strength of the soil with and without fibre reinforced fly ash matrix. With the addition of admixtures, the OMC is decreased and MDD is increased, the swelling pressure is decreased drastically and CBR values increased with the addition of admixtures showing an optimum improvement for soil with 0.5% fibre and 20% fly ash content. Thus the test results favoured the utilisation of waste materials such as fly ash and natural coconut fibre to enhance the suitability of stabilized expansive soil as subgrade for pavements.