Performance Evaluation of Cohesionless Soils Stabilized Using Metakaolin-Based Geopolymer for Infrastructure Applications

AbstractThe construction of infrastructure in coastal areas requires stabilizers to improve the characteristics of weak cohesionless geomaterials. Ordinary portland cement (OPC) is typically used to improve these geomaterials and provide a reliable foundation for infrastructure. However, the production of OPC is energy-intensive and has a high carbon footprint. Recently, geopolymers (GPs) have received attention as a sustainable alternative to OPC due to their low carbon footprint and ability to provide good mechanical properties. Their low carbon footprint is mainly attributed to the feasibility of using various waste and local materials such as fly ash (FA) and calcined clays for synthesizing GP. This study focused on investigating the effectiveness of metakaolin-based GPs as a stabilizer for cohesionless soils that are typically found in coastal areas. Its effectiveness was evaluated through unconfined compressive strength (UCS) and resilient modulus (MR) obtained from repeated load triaxial (RLT) tests. In addition, scanning electron microscopy (SEM) and magic-angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy were conducted to characterize the structure of the stabilized cohesiveness soils. The strength test results showed that the addition of 20 wt.% GP was effective in improving the UCS of cohesionless soils over 115 times after 3-day curing. The RLT test indicated that treated specimens with 20 wt.% GP had similar resilient moduli as soil samples treated with 4 wt.% OPC. Micro-characterization tests confirmed that the continuous network of GP gels significantly improved the UCS of GP-treated soils. Therefore, this study has shown that GPs are an effective and eco-friendly solution for improving the cohesionless geomaterials common in coastal areas.