Mechanical Properties of Soda-Lime-Silica Glasses Doped with Eggshell Powder

In this study, eggshell powder obtained from eggshell waste was used as a dopant in soda-lime-silica glass powders. Various eggshell-doped soda-lime-silica glass samples were produced through melting, and the effect of the eggshell powders on the mechanical properties of the soda-lime-silica glasses was investigated by micro-Vickers indentation tests. The X-ray diffraction results of the eggshell-doped glasses showed that, depending on the dopant content, different phases such as gypsum, nepheline, alunogene, aragonite, cristobalite etc. appeared. These results were different from the X-ray diffraction patterns of pure soda-lime-silica glass powders, where the phases observed included sodium aluminium silicate, sodium aluminum oxide, and silicon oxide. Although the elastic modulus of soda-lime-silica glasses increased with the addition of the eggshell powders, the dopant powders also caused an increase in the hardness of the glasses. Furthermore, it was found that the fracture toughness increased for soda-lime-silica glasses with 0.5 and 1 wt% eggshell powder, while it decreased for samples with eggshell powder contents >= 1 wt%. This behaviour could be explained by an increased depolymerization in the network connectivity of the glass when the amount of eggshell dopant increases.