Rheological characterization of clay–refractory waste composites for direct ink writing of ceramic structures

In the context of the circular economy and raw material sustainability, it is essential to explore alternative raw materials for the development of formulations with optimized physical and mechanical properties. This study focused on the rheological characterization of refractory ceramic waste blended with clay, aiming to optimize compositions for 3D printing. A mixture exhibiting the highest strength and resistance to shear stress was identified, making it a promising candidate for use in complex structural components. Mixtures with lower strength proved suitable for less demanding applications with simpler geometries. The presence of finer particles and lower bulk density of the filler led to increased viscosity and critical shear stress, contributing to higher mechanical stability. In contrast, mixtures with higher bulk density exhibited lower viscosity and reduced resistance to mechanical loading, despite demonstrating higher elasticity within the linear viscoelastic region. These findings represent a significant contribution to the effective selection and design of refractory ceramic formulations for additive manufacturing, tailored to the specific functional requirements of targeted applications. The research also demonstrated the feasibility of using waste-derived materials as feedstock for Direct Ink Writing (DIW) 3D printing of refractory ceramics, supporting both material circularity and sustainable manufacturing practices.