Geopolymer-based techniques for stabilization of microplastic contaminated expansive soil

Abstract The shrink-swell behaviour of expansive soils can lead to a range of structural problems, including foundation damage, cracking, and instability. Microplastic contamination in expansive soils is an emerging environmental concern with potential implications for soil behavior and structural stability. Alterations in soil properties, hydraulic conductivity, and shrink-swell behavior due to microplastics could lead to unpredictable soil movement, compromised soil stability, and increased risk of structural damage. The primary objective of the present paper is to review previous research using geopolymer-based stabilization techniques for expansive soils contaminated with microplastics. A detailed bibliometric analysis was performed using Scopus databases to examine global research trends, publication patterns, and significant contributions in this area. The review revealed more than 350 papers on geopolymer-based soil stabilization, with a remarkable rise since 2017, indicating a growing concern for sustainable soil stabilization. Geopolymer-treated soils exhibit significant improvement in Unconfined compressive strength, California bearing ratio and shrink-swell behaviour resistance, and hence they can be considered as a potential alternative to traditional stabilizers. The effectiveness of geopolymer stabilization is influenced by various factors, such as the type of precursor materials used (e.g., fly ash, metakaolin, slag), the concentration of alkali activator, curing condition and ratio of sodium silicate to sodium hydroxide. It further discusses the rising problem of microplastic contamination in soils, sources, environmental impacts, and its implications on soil behaviour. Microplastics substantially affect geotechnical behaviour through the increased hydraulic conductivity, decreased shear strength, and decreased capacity to hold water. The research emphasized an urgent need for optimized formulations of geopolymers that add value by providing improved soil stabilization, as well as a sustainable remediation method to enhance the soil contaminated with microplastics.