Utilization of Metakaolin-Based Geopolymers for Stabilization of Sulfate-Rich Expansive Soils

Abstract

The durability and performance of pavements and other lightweight structures constructed over expansive soils are persistent causes of concern due to moisture-induced volumetric fluctuations. Typically, traditional calcium (Ca)-based stabilizers, especially lime, effectively mitigate the problems associated with such problematic soils by reducing their swell-shrink potential and improving their strength properties. However, the treatment of sulfate-rich expansive soils using the Ca-based stabilizers results in detrimental heave due to the formation of a highly deleterious mineral, ettringite. This research study was performed to investigate the efficacy of utilizing an eco-friendly metakaolin-based geopolymer (MKG) stabilizer for treating sulfate-rich expansive soils. A comparative study was conducted by performing engineering tests such as free swell tests and unconfined compressive strength (UCS) tests on untreated, lime-treated, and geopolymer-treated soils for different curing periods. The effects of geopolymer dosage, curing period, and moisture intrusion on swelling characteristics and strength properties of treated soils were investigated. In addition, microstructural analyses were performed to study the changes in the soil after chemical treatment with geopolymer and lime. The results of engineering tests and microstructural studies indicate that geopolymer can effectively stabilize sulfate-rich expansive soils and could be used as a sustainable and eco-friendly alternative to traditional Ca-based stabilizers.