Improvement of engineering properties and environmental impact of fired clay bricks utilizing industry sludge waste

The increasing generation of industrial waste sludge poses a serious worldwide problem with detrimental effects on the environment and the economy. Effective utilization of waste sludge in sustainable construction practices offers a universal solution to mitigate environmental impacts. As the mining industry continues to extract clay from clay mines, the demand for sustainable practices in both clay mineral extraction and brick production is growing. Bricks are fundamental in masonry construction, and current research is exploring the integration of industrial waste materials into fired clay bricks to enhance their properties and mitigate environmental impacts. This study investigates the incorporation of waste sludge in brick manufacturing to assess its potential for reducing environmental burdens while maintaining technical performance. X-ray Fluorescence Spectrometry (XRF) analysis reveals that both clay soil and mosaic sludge contain high levels of silicon dioxide (SiO₂) and aluminum oxide (Al₂O₃), supporting their suitability as partial substitutes for clay soil. Incorporating up to 30% of body mill sludge (BS) and polishing sludge (PS) into the brick mix significantly enhances physical and mechanical properties, resulting in reduced shrinkage, increased porosity, and improved compressive strength, reaching up to 25 N/mm². Initial rate of suction tests shows values below 5 g/mm², indicating optimal water absorption characteristics. Various leachability assessments, including the Toxicity Characteristic Leaching Procedure (TCLP), Synthetic Precipitation Leaching Procedure (SPLP), and Static Leachate Test (SLT), confirm that bricks containing up to 30% BS and PS comply with United States Environmental Protection Agency (USEPA) and Environment Protection Authority Victoria (EPAV) standards for heavy metals, making them environmentally safe for use. Additionally, indoor air quality assessments confirm that these bricks meet Industry Codes of Practice on Indoor Air Quality (ICOP-IAQ) guidelines. This study demonstrates that using BS and PS as alternative raw materials offers a sustainable, cost-effective solution aligned with Sustainable Development Goals (SDGs), promoting cleaner production practices in brick manufacturing.