Production and characterization of thermal insulation bricks from drinking water treatment sludge and eggshells

Increasing consumption of natural resources and the release of various industrial/domestic wastes lead to environmental problems. In this thesis study, drinking water treatment sludge, an industrial waste for brick production, was used as an alternative to clay and eggshell was utilized as a pore-forming agent. Egg shells were incorporated to drinking water treatment sludge at different rates (0%, 5%, 10%, 15%, 20% and 25%) to prepare brick mixtures using the semi-dry method. The prepared mixtures were pressed with the help of a hydraulic press, dried at room temperature, and then the molded specimens were subjected to firing at 900˚C, 1000˚C and 1100˚C for 2 hours. Loss on ignition, apparent porosity, bulk density, water absorption, compressive strength and thermal conductivity properties of the fired brick specimens were determined. As the firing temperature and eggshell content increased, apparent porosity and water absorption values increased, while bulk density values declined. Compressive strength of bricks ranged from 14.7 MPa to 28.9 MPa, and it decreased as the eggshell content increased. In addition, there was an increase in compressive strength as the firing temperature increased from 900˚C to 1100˚C. In terms of compressive strength, the produced bricks meet the standard requirements for all eggshell additive ratios and firing temperatures. Thermal conductivity values varied between 0.961 W/mK and 0.615 W/mK. The lowest thermal conductivity value (0.615 W/mK) was reached in the brick with a firing temperature of 900˚C and 25% eggshell content. The results reveal that firing temperature and eggshell additive ratio are effective on the physical, mechanical and thermal properties of the produced bricks. According to experimental data, it is possible to employ eggshell as a pore-forming and drinking water treatment sludge as a clay substitute in brick production.