Effect of gradations of glass powder on engineering properties of clay soil geopolymer

While fine glass powder is a promising precursor for geopolymer production, its preparation is time-consuming and expensive. This study investigates using six different particle sizes of recycled glass – three uniform (fine and coarse) and three hybrid (combinations) – to reduce processing costs and optimize geotechnical and microstructural properties of clay-based geopolymers. Glass content varied from 0 % to 30 % by dry weight of soil, and a sodium hydroxide (NaOH) solution as an alkaline activator was used at three molar concentrations (2 M, 4 M, 6 M). A series of unconfined compressive strength (UCS), direct shear, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR) tests were conducted on samples. Results demonstrate that hybrid glass gradations containing both large (0.075–0.3 mm) and small (<0.075 mm) particles significantly improve the geotechnical properties compared to those with uniform fine particles, attributed to the enhanced dissolution of fine particles in the presence of coarser particles. The observed trends highlight the importance of combining particle sizes for optimal performance. This approach offers a more economical and effective alternative to traditional fine glass powder in clay soil geopolymers.