Eco-Friendly Stabilization of Sulfate-Rich Expansive Soils Using Geopolymers for Transportation Infrastructure

The utilization of traditional calcium-based stabilizers, such as lime or cement, for the treatment of sulfate-rich expansive soil, is a cause of concern for geotechnical engineering practitioners. The major problem associated with the application of such stabilizers is that when calcium ions from the stabilizers are exposed to soluble sulfate in the presence of sufficient soil moisture, they form a highly expansive mineral ettringite. This study aims to investigate the feasibility of stabilizing sulfate-rich expansive soils using a novel eco-friendly metakaolin (MK)-based geopolymer (GP) for the long-term durability of transportation infrastructure. Laboratory studies were undertaken to understand the influence of the geopolymer composition and dosage percentage for different curing periods in stabilizing the sulfate-rich expansive soils. Engineering tests such as the linear shrinkage and unconfined compressive strength tests were performed to compare the behavior of natural, lime-stabilized, and geopolymer-stabilized soils over different curing periods. Microstructural characterization using field emission scanning electron microscopy (FESEM) with energy-dispersive x-ray spectroscopy (EDXS) was performed to compare the morphological and chemical changes between geopolymer-treated and untreated natural soil. The results indicated that the geopolymer treatment of sulfate-rich expansive soils could result in significant reductions in shrinkage and subsequently help in a greater strength gain than lime-treated high-sulfate soil.