Co-utilisation of recycled ceramic waste and sawdust in refractory bricks: thermal–mechanical trade-offs and resource recovery potential

The growing demand for low-cost and eco-friendly refractory materials has generated interest in locally available waste materials as alternatives to conventional refractories. This study investigates recycled ceramic waste and sawdust in refractory bricks, assessing their trade-off between mechanical strength and thermal insulation. Five formulations were prepared by maintaining clay at 35 wt% and varying the ceramic waste-to-sawdust ratio before firing at 1100 °C. The bricks were evaluated for water absorption, compressive strength, thermal conductivity and dimensional stability at 1100 °C. Water absorption increased from 7.8% to 22.4% as sawdust increased from 0 to 20 wt%, while compressive strength and thermal conductivity decreased from 18.6 to 6.7 MPa and 0.92 to 0.38 W/m·K, respectively. These trends are consistent with the proposed pore-forming effect of sawdust during firing. The formulation containing 55% ceramic waste, 35% clay and 10% sawdust provided the most balanced performance, with 12.8 MPa compressive strength, 0.63 W/m·K thermal conductivity, 13.9% water absorption and no visible deformation or cracking at 1100 °C. The findings demonstrate a thermal–mechanical performance envelope from redistributing a fixed 65% waste-derived fraction between ceramic waste and sawdust, indicating resource-recovery potential while recognising the need for further environmental and service-level assessment.