Use of waste husk from millet grain cultivation in the production of fired clay bricks

The consumption of colossal quantities of materials in the building industry has advanced the swift depletion of clean clay reserves. The use of organic additives in brick production is conserving clay resources. In addition, in some cases, it can lead to improvements in some material properties, such as decreasing thermal conductivity and increasing the capacity of the ceramic material in terms of thermal insulation. In the present investigation, waste millet husk (WMH) was incorporated in different proportions to clays to ascertain its influence on the fired brick properties. The raw materials were characterized for their physical, chemical, and thermal properties and found suitable for use in fired brick production. Additionally, the prepared modeled brick samples were tested for their physico-mechanical properties. The results indicated that linear shrinkage and weight loss increased, whereas bulk density decreased from 2.06 to 1.58 g/cm³ depending on WMH incorporation amount in the clays and firing temperature. Similarly, compressive strength reduced by up to 68%. Thermal conductivity beneficially reduced by 42% with the addition of 16 wt.% of WMH. The best results in terms of mechanical properties were obtained with 4 wt.% of the WMH. In terms of thermal insulation, the best results were exhibited in the samples admixed with 16 wt.% of WMH. The results showed that porosity and bulk density were critical determining factors that directly influence the bricks physico-mechanical properties.