Effect of Different Gypsum Particle Morphologies on the Properties of Lightweight Polyethylene/Fly Ash/Gypsum Composite

In recent years, the development of sustainable materials from industrial mineral wastes or by-products have gained importance to achieve carbon neutrality. Among these industrial wastes, fly ash (FA) and flue gas desulfurization (FGD) gypsum are two significant by-products generated in large quantities by coal-fired thermal power stations, and their valorization has become a critical research topic. This study focuses on the development of composite materials using fly ash and FGD gypsum in combination, with low-density polyethylene (PE) as the binder. In addition, borogypsum (BG), which has a higher particle aspect ratio than FGD gypsum, was also used instead of FGD gypsum, and changes in the composite properties were evaluated. With the addition of borogypsum, 32.8% higher strength values were obtained compared to the series containing FGD gypsum. The results indicate that composite structures incorporating both phases yield a more balanced microstructure and enhanced mechanical performance compared to those in which UK, FGD, or BG is used individually. Additionally, SEM images illustrate the elongation and breakage of the PE binder matrix during fracture, confirming its dominant role in strength development. It was concluded that particle morphologies and loose particle density of the different gypsum filler materials in lightweight Polyethylene/Fly Ash/Gypsum composites are important factors. It should also be noted that the particle size distributions of two different gypsums were also effective in determining the physical-mechanical properties.