Improving expansive clay subgrades using recycled glass: Resilient modulus characteristics and pavement performance

Abstract

The scarcity of sound soils, especially in urban areas, often forces engineers to construct the pavement on problematic subgrade soils such as expansive clays. The associated cost involved in replacing the existing problematic soil is avoided by adopting treatment techniques. In this study, a type of high plasticity expansive clay was mixed with 10, 20, and 30% sand-size recycled glass (RG) as a non-chemical soil treatment approach. An extensive investigation comprising experimental works, numerical modeling, and pavement performance analysis was undertaken. After determination of the physical properties of clay and RG, resilient modulus characteristics of clay and the three clay-RG mixtures were carried out through an experimental program. Subsequently, the obtained resilient modulus data sets were incorporated into a finite element analysis program in order to analyze the stress-strain response of pavement models founded on clay and RG-treated subgrades. The compressive and tensile strains achieved through the analysis of the pavement models under traffic loads were next used to compare each pavement model with respect to fatigue and rutting performances. The experimental results showed up to a 113% increase in resilient modulus of clay by the addition of 30% RG. The outcomes of the analysis on pavement systems modeled using the experimental input showed a considerable reduction in compressive and tensile strains by treating the clay subgrade with RG. Consequently, the strain reduction exhibited a significant increase in fatigue life and rutting life of pavements founded on RG treated clay subgrades. The outcomes of this research aim to encourage the construction industry to consider the utilization of environmentally clean recycled aggregates, such as RG, for improving subgrades with problematic soils and hence, promote sustainable construction materials and approaches.