Utilization of Pine Needle Waste in Insulating Clay Bricks: Evaluation of Physical, Mechanical, and Thermal Properties
摘要
This study investigates the utilization of pine needle waste as a sustainable additive for producing thermally insulating clay bricks from Nsukka clay, Nigeria. The raw clay, containing 25.3 wt.% Al₂O₃ and 54.9 wt.% SiO₂, was blended with 0–20 wt.% pine needle powder and fired at temperatures ranging from 900 to 1200 °C. The optimum composition was identified as 80% clay and 20% pine needle additive, fired at 1000 °C. Compared to the pure clay brick, the addition of 20% pine needle powder increased the apparent porosity from 12.3% to 16.3% and water absorption from 6.5% to 8.9%, while decreasing the bulk density from 1.87 g/cm3 to 1.84 g/cm3, modulus of rupture from 27.6 kgF/cm2 to 18.1 kgF/cm2, and thermal conductivity from 0.53 W/mK to 0.35 W/mK. The refractoriness of this composition was 1510 °C, which falls within the acceptable range for insulating clay bricks. XRD and SEM analyses confirmed the development of crystalline aluminosilicate phases and increased pore distribution, respectively, supporting enhanced thermal insulation. The results demonstrate the feasibility of converting abundant pine needle waste into a low-density, energy-efficient insulating clay brick material suitable for sustainable construction applications.