Additive manufacturing of ceramic bricks with glass waste: thermal performance, sound absorption, and heat transfer evaluation of ceramic wall systems

The development of energy-efficient building components requires materials with optimized thermal resistance and controlled heat transfer mechanisms. This study investigates the thermal performance of ceramic bricks fabricated via extrusion-based additive manufacturing using yellow kaolinitic clay and recycled glass waste. Solid and hollow geometries were designed to tailor internal architecture and improve thermal insulation behavior. Thermal conductivity was measured using a transient plane source method and further evaluated at the wall scale through controlled furnace experiments and finite-element simulations. Results show that the addition of 10-20 wt% glass reduces thermal conductivity, while a further increase to 30 wt% leads to a rise associated with microstructural densification. At the component scale, hollow walls exhibited lower effective thermal conductivity (0.23 W·m -1 ·K -1 ) than solid walls (0.26 W·m -1 ·K -1 ) under steady-state conditions, resulting in a 13.3% increase in thermal resistance and reduced external surface temperatures. These effects are attributed to the combined influence of internal air cavities and heat-flow path disruption. Mechanical tests confirmed adequate compressive strength (11.19 MPa for hollow bricks), while acoustic absorption remained moderate and largely unaffected by composition. The results demonstrate that geometrically engineered ceramic bricks produced by additive manufacturing can improve thermal insulation performance, offering a viable approach for energy-efficient building envelopes.