Fabrication of lightweight and thermal insulation roof tiles using industrial wastewater sludge

This study investigates the potential application of industrial wastewater sludge (IWS) as a viable alternative to clay in the production of lightweight roof tiles, aiming to improve thermal insulation and mitigate environmental impacts. Six distinct tile compositions were created by substituting kaolin clay with 5 %, 10 %, 15 %, 20 %, 25 %, and 30 % IWS. The specimens were dehydrated at 110 °C and then sintered at 1,000 °C, 1,100 °C, and 1,150 °C. The physicochemical parameters, including bulk density, apparent porosity, water absorption, transverse breaking strength (TBS), and modulus of rupture (MOR), were systematically assessed. The findings indicated that augmenting IWS concentration resulted in increased porosity and water absorption, concurrently diminishing bulk density and thermal conductivity. Thermal conductivity reduced from 0.95 W/m K (0 % IWS) to 0.265 W/m K (30 % IWS), indicating enhanced insulation characteristics. Tiles with (0–30 %) IWS, burned at 1,150 °C, conformed to ASTM C1167 criteria, attaining a TBS higher than 890 N (minimum requirement: 890 N) except 30 % IWS burned at 1,000 °C. High IWS replacement had an adverse effect on mechanical strength and durability. The results indicate that the use of 30 % IWS at 1,150 °C enhances the equilibrium among mechanical integrity, insulation efficacy, and long-term sustainability, which makes it a viable option for energy-efficient construction applications.