Utilization of coal gangue for the production of brick

Coal gangue, an industrial solid waste discarded from coal mining and processing, was used as the sole raw material to prepare brick. The coal gangue was crushed, homogenized, milled and then pressed into green compacts. The dried compacts were sintered at different temperatures for 2 h. The obtained brick samples were characterized with X-ray diffraction, scanning electron microscopy, and physico-mechanical properties. Results indicate that bricks are composed of glassy phase, crystals of quartz, mullite, cordierite, as well as pores. The phase components, microstructure, and physico-mechanical properties of the bricks vary significantly with the sintering temperature. The linear shrinkage, bulk density, compressive strength, and flexural strength increase gradually with the sintering temperature enhancing from 900 to 1100 °C, and rise sharply to the maximums at 1200 °C, then drop considerably at 1250 °C. The water absorption value exhibits an opposite tendency. Bricks meeting the Chinese Standard GB 5101-2003 were sintered at 1100–1250 °C. The brick sintered at 1200 °C possesses the optimal properties, with the water absorption and compressive strength values of 3.65 % and 45.61 MPa, respectively. The radioactivity index and leaching toxicity of sintered bricks prepared under the optimum condition were all below the corresponding standards.