Stabilization of expansive subgrade soil by using fly ash

Abstract

Expansive soils are efficacious chemically and are those soils which swell and shrink appreciably that engendering volume changes hinging on water content. So, it is imperative to stabilize the expansive soil in order to fortify the pavement performance as well as to reduce the maintenance cost. In this regard, waste product like fly ash is selected as an admixture, to mix with the expansive soil for its stabilization (which forms homogeneous stabilized sub grade layer) in the current study. The present study involves conduction of laboratory tests in order to obtain the Atterberg Limits, California Bearing Ratio (CBR) and Unconfined Compressive Strength (UCC). The experimental results depict that, the Atterberg limits, Plasticity Index & Free Swell Index are decreasing with the inclusion of fly ash from 0%–20% to the Black Cotton Soil. CBR value of untreated soil is perceived as 2.189%, whereas the treated soil with fly ash found to have a maximum of 2.33% (10% fly ash), i.e., increased to 6.0% from initial value. Unconfined compressive strength (UCC) of untreated soil is 0.1688 N/mm2 and the treated soil with fly ash attains to a value of 0.333 N/mm2 (10% fly ash) i.e., increases by 49.30% from the initial value and further down drift is observed in both CBR and UCC values. The study infers that, the use of fly ash up to 10% is recommended to mix with the black cotton soil, where it can be used in the construction of pavement and any other foundation works.