Recycling of waste: a light review on the application of egg shell waste in composite formation and the characterization of crushed egg shell waste as filler material for epoxy resin

Abstract

This study investigates the prospects of using raw crushed eggshell waste (CES) as a sustainable filler in epoxy resin composites, extending beyond the limitations of the literature by addressing macroscopic particles (> 100 μm) without calcination. The 3%, 6%, and 9% CES loading composites were fabricated via hand lay-up and were evaluated for mechanical, microstructural, and durability performance. Results showed 60% enhancement in hardness (37.5 to 60 HRB) and 12.4% enhancement in tensile strength (9.7 to 10.9 N/mm²) at 9% CES, owing to improved load distribution and interfacial adhesion. Microstructural investigations (SEM/EDS, XRD) confirmed CaCO₃ incorporation and also indicated agglomeration problems with higher loading. Chemical resistance tests indicated improved resistance to acid at 9% CES (30 mg loss in weight after 72 h), while water absorption decreased by 28.6% when compared to pure epoxy. Statistical optimization using Response Surface Methodology (RSM) indicated 9% CES to be optimum for minimum degradation. The study underscores untreated CES’s dual potential as reinforcement and green filler, offering reduced density (11.5% lower than epoxy) and enhanced durability in corrosive or wet environments. The findings advocate CES-epoxy composites as eco-friendly alternatives to conventional materials, in alignment with global waste valorization and resource efficiency goals.