The Effect of the Addition of Eggshell Residues in Mass Formulation for Ceramic Coating

In this study, we developed formulations of a ceramic coating from clay, kaolin, quartz, talc and feldspar as a standard formulation with the addition of eggshell residue to improve the mechanical characteristics of the product. The addition of eggshell residue is justified as it will contribute to filling the formulation’s interstices. It would also help decrease the sintering temperature due to the high presence of calcium oxide in its composition. Samples with the ceramic coating (45% by weight of feldspar; 30% by weight of clay; 15% by weight of kaolin; 7% by weight of quartz; 3% by weight of talc; and additions of 5%, 10% and 20% by weight of eggshell residue) were pressed uniaxially at 70 MPa for 30 s; dried at 110 °C for 24 h; and sintered at 1000 °C, 1100 °C and 1200 °C. The main mineralogical phases (microcline, mullite, quartz and anorthite) of the sintered samples were identified by X-ray diffraction (XRD). After evaluating the physical-mechanical properties (water absorption, linear shrinkage, apparent porosity and resistance to flexion), it was observed that the incorporation of eggshell residue (5%, 10% and 20%) resulted in a significant loss of the desired physical and mechanical properties. A loss of over 50% of mechanical strength was obtained.