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The optical properties of soda-lime-silica glasses doped with eggshell powder were investigated using UVvisible and the Fourier transform infrared spectroscopies. Pure soda-lime-silica glass, which is colorless and transparent, turned dark green after the addition of the eggshell powder. When the eggshell powder content was ≥ 3 wt%, the glass became translucent. The maximum wavelengths in the UV spectra of the soda-lime-silica glasses doped with 0.5, 1, 3, and 5 wt% eggshell powder were observed at 300.20, 277.40, 284.40, and 312.40 nm, respectively. The Fourier transform infrared spectra of the eggshell-doped soda-lime-silica glass samples were very similar to that of the base undoped glass. The bands at approximately 770-820 cm −1 could be attributed to the Si-O-Si symmetric stretching of the bridging oxygen between the tetrahedra, while the bands at approximately 970 cm −1 were related to the Si-O-Si antisymmetric stretching of the bridging oxygen within the tetrahedra.

In this study, the mechanical properties of soda-lime-silica glasses were investigated by using micro-Vickers indentation tests, while varying the amount of peanut shell powder added to the glass. Peanut shell powder was obtained by grinding peanut shells. It was added as a dopant to glass at 0.5-5 wt.%, with the final glass samples being produced by melting. Peanut shell addition had led to a decreased density of the soda-lime-silica glasses, and X-ray diffraction data of the peanut shell-doped soda-lime-silica glasses indicated the presence of two crystalline phases, namely, anorthite (Na0.45(Ca0.55Al1.55Si2.45O8) and magnesium aluminum silicate (MgAl2Si3O10)6. The Young's modulus values of the soda-lime-silica glasses increased along with the amount of peanut shell powder added. Peanut shell addition to the soda-lime-silica glasses has also caused increased hardness. Fracture toughness values of these glass samples were in the range of 0.91-1.04 MPa m 1/2 . Thus, the mechanical properties (e.g. E and KC) of soda-lime-silica glasses could be enhanced through peanut shell addition.

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 microVickers 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.