Preparation of eco-friendly construction bricks from hematite tailings

With the objective of reducing the negative impacts on environment and utilizing the secondary resource of tailings, the possibility of making construction bricks by using the hematite tailings from western Hubei province of China was investigated. Besides hematite tailings, the additives of clay and fly ash were added to the raw materials to improve the brick quality. Through the process of mixing, forming, drying and firing, the bricks were produced. The optimum conditions were found to be that the hematite tailings content were as high as 84%, forming water content and forming pressure were respectively in the range of 12.5–15% and 20–25 MPa, and the suitable firing temperature was ranged from 980 to 1030 °C for 2 h. Under these conditions, the mechanical strength and water absorption of the reddish fired specimens were 20.03–22.92 MPa and 16.54–17.93%, respectively, and the other physical properties and durability were well conformed to Chinese Fired Common Bricks Standard (GB/T5101-2003). The phases and morphologies of the green tailings and fired specimen were characterized by XRD and SEM. The results showed that the main mineral phases of the product were hematite, quartz, anorthite and tridymite, which were principally responsible for the mechanical strength of bricks.