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Abstract This investigation addresses the effect of sludge from water treatment plants as partially replacing cement on the mechanical properties. Various mixtures of sludge powder (SL) after heated treatment at 200°C, 300°C, and 500°C are produced by partially replacing cement with 0%, 5%, 10%, 15%, 20%, and 25 wt%. SL after heated treatment at 200°C with 0%, 5%, 10%, 15%, 20%, and 25 wt% was replaced with 10% liquid sodium silicate. The program includes the substitution of cement with 5% un-hydrated lime and 10% silica fume at sludge powder after heated treatment at 200°C with 0%, 5%, 10%, 15%, 20%, and 25 wt%. A series of laboratory tests were performed to investigate the mechanization of strength development which included compressive strength, splitting tensile, flexural strength, Scanning electron microscope (SEM), Energy dispersive X-ray spectroscopy (EDX) and mapping. Generally, the treatment of SL powder with increased heat has a positive effect on its strength. The treatment of SL powder at 500°C improved the strength and the mechanical properties compared with SL powder after heating at 200°C and 300°C. The results showed that using 5%, 10% sludge in concrete increased the strength and then decreased at 15-25% of sludge. Increase the heat treatment of the sludge led to increasing the strength. The use of the sludge after heat treatment at 300°C improved the strength more than the sludge after heat treatment at 200°C. The use of the sludge after heat treatment at 500°C improved the strength and the mechanical properties the most. The use of the sludge after heat treatment at 300°C and silica fume improved the strength and the mechanical properties significantly. |