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Abtract Aluminum slag waste generated from the smelting process of bauxite was used to prepare roof tiles samples. Clay was substituted by slag waste in percentages reaching 40% in the basic mix and the plasticity of the obtained mud was determined. This was followed by pressing the mud in steel molds and drying. The effect of waste addition on drying shrinkage was subsequently assessed. Firing of the green bodies was carried out at three temperatures (900, 1000 and 1100 °C) and hour soaking at each temperature. Fired roof tile properties improved on increasing the percentage of alumina sludge and firing temperature possibly because of the presence of high amounts of fluxing oxides in aluminum slag. This caused a drop in porosity that increased the mechanical strength of tiles. The results showed that the substitution of clay by 40% waste and firing at 1100 °C resulted in products conforming to ASTM C-1167 for clay type roof tiles. Cold water absorption dropped to 12%, below the maximum permissible limit of 15%, the value of Saturation Coefficient was 0.83, below the 0.86 limit and the obtained breaking strength of 3370N significantly exceeded the minimum requirement of 890N.

Most of the research of building materials companies at present focuses on recycling waste to minimize the cost of their products and for the safe disposal of these wastes. In this work, the by-pass cement kiln dust (BCKD), the dust that is discarded from the kiln system was used for the preparation of roof tiles. It is partially used to substitute clay in percentages from 5 % up to 25 %. to prepare roof tiles abiding by ASTM C1167 for two objectives, the safe disposal of waste and the production of low-cost roof tiles. The raw materials were assessed by particle size analysis, XRD, and XRF. The mud was poured into moulds with dimensions of 150 * 30 * 25 mm3 and pressed under a pressure of 10 MPa then dried. The dried samples were fired to temperatures 1000, 1100, and 1150℃ with a soaking time of one hour for each temperature. The linear firing shrinkage, water absorption, bulk density, and breaking strength were measured to determine the properties of the fired specimens. The initial rate of absorption and runoff properties were also determined for the optimal samples. The results showed that samples containing 8% and 12% of BCKD waste that fired at 1100°C and 1150°C had cold water absorption of 14% and a saturation coefficient of 0.85, both of which were below the maximum values of the standard limits. Furthermore, the measured breaking strength of about 2700 N was much higher than the necessary minimum value. The results showed that samples met the requirements of ASTM 1167 for clay-type roof tiles containing 8% BCKD waste and fired to 1100℃. For economic and environmental benefits, 1100℃ firing temperature is recommended than 1150℃. The initial rate of absorption was found to be 2.8 kg.m-2 and the runoff properties were found to be 0.02 mg.L-1, 7.53, 110.5 mg.L-1 for total dissolved solids, pH and total solids respectively.