Geopolymer stabilization of sandy soils using ground granulated blast furnace slag and waste glass powder: Mechanical and microstructural performance

Sustainable improvement of sandy soils remains a significant challenge in geotechnical engineering, driven by the growing need to minimize the environmental footprint of conventional stabilization methods. This study employs ground granulated blast furnace slag (GGBS) and waste glass powder (WGP) to synthesize a geopolymer stabilizer designed to improve the engineering properties of poorly graded sand. The experimental program involved incorporating a binder (GGBS and WGP) into the soil at dosage levels ranging from 10 wt.% to 70 wt.%. The alkaline activator concentration was kept constant at 6 M, utilizing sodium hydroxide (NH) and sodium silicate (NS). The stabilized specimens were tested after being cured for 7, 28, and 91 days. The unconfined compressive strength (UCS) test was employed to assess mechanical performance, while X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) were used to examine the microstructural development. The results indicate that binder/soil ratios in the range of 40 % - 50 % provide the highest strength, depending on both the type of alkaline activator and the WGP replacement level, with the optimal WGP substitution for GGBS identified as 25 %. Microstructural analysis revealed that this improvement is mainly attributed to strong pozzolanic reactions and the formation of aluminosilicate gels. These findings demonstrate that geopolymers based on GGBS and WGP provide an effective and sustainable solution for soil stabilization, reducing environmental impacts and advancing greener construction practices.