Clay Stabilization Using Fly‑Ash Geopolymer Binders: Optimization of Alkali Activators and Microstructural Insights

This research investigates the application of fly ash geopolymers as sustainable binders for supporting high plastic clay (HPC). The study emphasizes on optimizing the liquid alkali activator (LAA) ratio, NaOH molarity (1M, 3M, 5M), and curing durations (7, 14, and 28 days) to improve mechanical and durability properties. Unconfined Compressive Strength (UCS) tests showed marked enhancement in strength with increasing molarity and curing time, indicating effective stabilization of high plastic clay (HPC) through geopolymerization. The Elastic Modulus (E₅₀) increased proportionally, increasing the rigidity of the treated soil. Microstructural analysis using SEM revealed the formation of sodium aluminosilicate hydrate (N-A-S-H) gels with increased crystallinity, particularly at higher NaOH concentrations. This study summarizes that fly ash-based geopolymer stabilizers provide a sustainable and effective solution for improving the engineering properties of high plastic clay (HPC), adding to environmentally friendly geotechnical practices.