Enhancing Mechanical Characteristics of Fly Ash and Fly Ash–Stone Dust Using Geopolymerization Technique

Abstract Geopolymer, an inorganic aluminosilicate polymer, is considered a sustainable construction material. However, a notable research gap still persists in minimizing the use of alkali activators and calcium-based additives by using suitable industrial byproducts such as fly ash and stone dust. The present study aimed to optimize various geopolymerization parameters (concentration of solutions, temperature, and curing period), explore the strength and durability of geopolymer-based materials, and find out the mechanisms by conducting microlevel investigations and physicochemical analyses. The results reveal that geopolymer ratios of 1:0.25 and temperature of 100°C are found to be optimum based on compressive strength for fly ash and stone dust and their combinations. The samples subjected to freeze–thaw (F-T) cycles reveal only a minor loss in compressive strength (i.e., 4%–6%) for all compositions, demonstrating the resilience of geopolymer building materials even in adverse environmental circumstances. Further, the longevity potential of the optimized compositions is evaluated at different curing periods. Additionally, microlevel investigations (X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and mercury intrusion porosimetry) confirm the formation mechanism of reaction products and microstructural changes. Further, the potential of hydrogen and electrical conductivity values assess the physicochemical properties for understanding their effect on geopolymer reactions and the mechanical behavior of compositions.