Strength, durability, thermal and run-off properties of fired clay roof tiles incorporated with ceramic sludge

This study explores the possibility of substituting clayey raw materials using ceramic sludge in clay roof tile production. The tile specimens were manufactured in an industrial scale plant by replacing clay with ceramic sludge: 0%, 10%, 15%, 20% and 25% (by weight). Strength properties (transverse breaking strength, modulus of rupture, bulk density), durability properties (water absorption, water penetration, salt crystallization, efflorescence, acidic and alkaline resistances) and run-off qualities (Ph, total solids, BOD, heavy metal concentration) were examined. Thermal properties of the sludge incorporated tiles were investigated and compared with the conventional tiles. Bulk density reduces with increasing the sludge content, which is a favorable property of roof tiles. Transverse breaking strength was optimum at 20% sludge, indicating 22.9% increment compared to the conventional tile. Clay replacement up to 20% is acceptable, satisfying water absorption and penetration in standards. No efflorescence and Sulphuric acid attack were disturbed for any specimen. At 12:00 noon, the tile with 20% sludge reduced indoor temperature by 2.8 °C, providing more comfortable shelter compared to the conventional roof tiles. For the 25% sludge incorporated tiles, run-off showed 120.2 mg/l total solid concentration, 7.36 Ph value and 5 mg/l BOD5 value, 0.01 mg/l, 0.05 mg/l, 0.06 mg/l, 0.04 mg/l Cd, Cu, Pb and Zn concentrations, respectively; while for the other tiles, run-off had lesser concentrations, which are favorable for rain water harvesting process. With 20% sludge, tiles achieved better structural, durability and thermal properties compared with the conventional tiles while satisfying the standard limits of run-off qualities.