Utilization of drinking water treatment sludge and eggshells as clay substitute in porous brick manufacturing: Target zero waste

Abstract

The increasing demand for building materials and the depletion of natural resources have prompted the search for sustainable alternatives, particularly to clay. Drinking water treatment sludge (DWTS) and eggshells are two abundant solid wastes that pose environmental challenges due to their disposal difficulties. This paper propes a novel and eco-friendly approach to brick production by simultaneously using DWTS as substitute for clay and eggshells as pore-forming agent-an underexplored combination in literature. To prepare brick mixtures using semi-dry method, eggshells were incorporated to DWTS at rates ranging from 5 % to 25 %. Molded brick samples were fired at 900 degrees C, 1000 degrees C and 1100 degrees C for 2 h. The findings indicated that increasing eggshell content and firing temperature led to higher apparent porosity and water absorption. Compressive strength decreased from 28.9 MPa to 14.7 MPa however it was still within acceptable limits. At 900 degrees C and 25 % eggshell content, the lowest thermal conductivity (0.615 W/mK) was recorded, suggesting enhanced thermal insulation potential. Experimental results demonstrate the potential of DWTS and eggshells to be jointly valorized as sustainable raw materials in brick manufacturing, contributing to both waste management and low-carbon construction materials.