Utilization of the sludge derived from dyestuff-making wastewater coagulation for unfired bricks

The object of this work was to explore the feasibility of using the sludge derived from dyestuff-making wastewater coagulation for the preparation of unfired bricks with four typical cements including Portland cement, ground silicate cement clinker, alumina cement and slag cement. The interaction between the sludge and cement were studied based on X-ray diffraction, thermal analyses, compressive strength measurements, freeze–thaw tests and leaching tests. The experimental results showed that the cement solidified sludge was capable of reaching all performance criteria for unfired bricks at a cement/dry sludge/water ratio of 1:0.5–0.8:0.5–0.8. The compressive strengths of alumina cement solidified sludge overpass 40 MPa, higher than those of other cement solidified sludges. It is expected that the unfired bricks of the sludge and alumina cement can be used for the pave of pedestrian road.

Research highlights
► Sludge derived from dyestuff-making wastewater coagulation was used for the preparation of unfired bricks.
► Cement solidified sludge was capable of reaching all performance criteria for unfired bricks.
► The compressive strengths of alumina cement solidified sludge were higher than those of other cement solidified sludges.
► The unfired bricks of the sludge and alumina cement can be used for the pave of pedestrian road.