Evaluation of Lime-Cement-Fly Ash Stabilization in Curtailing the Dispersive Potential of Australian Sodic Soil

Abstract

Sodic soils account for nearly one third of Australia’s land mass and pose several challenges such as dispersion and erosion, thus destabilizing vast eco-systems. Chemical stabilizers such as lime, cement, fly ash etc., improve the mechanical performance of such soils and reduce their dispersivity. This study presents the results of a novel triple blend stabilization method for strongly sodic soil with Exchangeable Sodium Percentage (ESP) in 15-25%. Lime, cement and fly ash (LCF) were adopted in four different blend proportions to achieve at least 1.5MPa Unconfined Compressive Strength (UCS) as per Transport and Main Roads (TMR) specification. The results indicate that B4-4% with 20/50/30 LCF yielded the best performance with lowest shrinkage of 2.9% and higher dry density 2126.4 kg/m3. Regression analysis of UCS results projected that an additional 2.53% soil-stabilizer replacement is required to improve the performance of B4 from 0.86MPa to reach 1.5 MPa. Scanning Electron Microscopy (SEM) analysis showed needle-like ettringite crystals and Calcium-Silicate-Hydrates (CSH) net-like structures over 28-day curing. X-Ray diffractometry (XRD) indicated a drop of 20.8% in Na+ and 20.3% increase in Ca++. The triple blend stabilization technique enhances UCS performance by 167% with a less than 5% of the total volume of the additives when compared to the single and double blends.