Improvement of traditional clay bricks’ thermal insulation characteristics by using waste materials

This study aims to improve clay bricks' thermal insulation properties by using waste materials. Laboratory scale samples were produced by an extrusion process, which simulates a feasible industrial production technique. The study results reveal that the unit weight of brick was reduced, and thermal properties were improved by introducing grapevine twig and poplar dust by forming pores in the brick mud after firing. When the substitution ratio of waste materials increased from 2.5 %–15 % by volume gradually, it was determined that the thermal conductivity coefficient (λ), dry bulk specific gravity, and compressive strength value of the clay brick decreased. However, the moisture content for extrusion and the water absorption ratio increased. The amount of waste material in clay brick mud was optimized, and the effect of these waste materials on the plastic and hardened properties of clay bricks were investigated. As a result, the optimum mix ratio of grapevine twig and poplar dust was 7.5 % by volume considering extrudability, physical, thermal and mechanical properties of the final product. It was shown that the bricks' weight was reduced by 25 %, and the thermal conductivity coefficient was decreased by 22 % at a 7.5 % substitution ratio by volume, respectively. With the addition of waste materials, drying shrinkage values decreased due to waste materials restricting effect, while firing shrinkage values increased due to increased porosity. Moreover, it was determined that these two waste materials could be used at similar dosages because they have introduced similar characteristics to traditional clay bricks.