Integrated Performance Evaluation of Sludge-Based Bricks: A Sustainable Alternative to Conventional Masonry Units

Abstract

Abstract Rapid urbanization and industrialization have led to a substantial increase in wastewater sludge generation, creating major environmental and disposal challenges. Simultaneously, conventional brick manufacturing consumes large quantities of natural clay, contributing to depletion of fertile soil and ecological imbalance. This study investigates the feasibility of utilizing dried wastewater sludge as a partial replacement for natural clay in sustainable brick manufacturing. Sludge-based bricks were prepared with varying sludge proportions (20-24%) and evaluated through engineering and geotechnical tests, including crushing strength, moisture, bulk density, durability, liquid limit, and plasticity characteristics. Experimental results revealed that controlled sludge addition can produce lightweight (1618-1685 kg/m3) and environmentally sustainable bricks with acceptable physical and mechanical properties. Moderate sludge replacement levels (up to 20%) exhibited satisfactory compressive strength (5.7 MPa) and durability while reducing the consumption of virgin clay materials. Furthermore, sludge incorporation contributed to lower bulk density and enhanced waste utilization efficiency. However, higher sludge contents (22% and 24%) adversely affected strength and water absorption characteristics, highlighting the need for optimum replacement levels. The study also revealed that sludge incorporation reduces brick density, and lowers CO₂ emissions. The findings demonstrate the potential of wastewater sludge reuse in brick production, supporting sustainable waste management, circular economy principles, and green construction practices.