Strength Performance of Alkali Activated Binder and Cement Stabilized Expansive Soil: A Field Study on Subgrade Layer

Abstract

The dual character of expansive subgrade soil, which includes swelling and shrinkage, causes a premature collapse on the pavement surfaces. The scopes of the current study include comparison of the field performance of cement and alkali activated binder (AAB) stabilized expansive subgrade soil. To assess the strength properties, a 12 m long semi-field test section with expansive soil that has been treated with AAB, cement, and untreated expansive soil is built. Steel slag and fly ash are used as dry pozzolanic precursors in AAB, while sodium silicate and sodium hydroxide are used as an activator solution in a 0.4 water:solids ratio. AAB provides twin benefits of reducing the need for traditional binders and lowering the cost of fly ash/slag disposal in landfills. It also has a less carbon footprint than a PC-based binder, stronger mechanical strength and longer durability. By embedding a number of stress metres and strain gauges in the subgrade layer and applying a load through a dual-wheel truck load (12-tonne rear axle load) on the field track, the in-situ subgrade strength behaviour is assessed. On samples taken from the field section, the effects of AAB, curing duration, and the proportion of steel slag/fly ash in the alkaline soil mixture on the geomechanical properties of soil are examined. Additionally, using KGP-BACK software, falling weight deflectometer investigations were conducted to assess the elastic moduli of each layer. It has been noted that subgrade layers treated with AAB had larger elastic moduli than those treated with cement or left untreated. In comparison to cement-treated soil, the AAB mixture’s subgrade strength is increased by 23-26% by the combined addition of slag and fly ash. Based on the semi-field test section studies, recommendations for the effective application of AAB stabilisation for expansive soils as subgrade are given.