Effect of CaO sources derived from different solid waste on the minerals and properties of prepared anorthite ceramics

Such typical high CaO content solid wastes as marble sawdust, red mud and steel slag taken as CaO sources, were used to prepare anorthite ceramics respectively with high silica and high alumina solid wastes (coal gangue and furnace slag). Their crystallization and densification during the high temperature sintering process and final properties were analyzed. The results showed that minerals containing CaO in the three high CaO solid wastes were respectively calcite and dolomite in the marble sawdust, aragonite and perovskite in red mud, calcite and dicalcium silicate in steel slag. Anorthite phase as main crystals was generated at the sintering temperature equal to and above 1 100 ℃ in all prepared ceramics. But the secondary crystals in the ceramics were different in type and quality. Among them, lots of pyroxenes were from marble sawdust in the ceramics, a small amount of pyroxene and hematite from red mud, little hematite from steel slag. Bending strength and water absorption rate of all the ceramics met the requirement of national standards of ceramic brick. Ceramics from steel slag and red mud possessing lower sintering temperature at about 1 160 ℃, contributed to their impurity flux components of Fe₂O₃ or/and Na₂O. The ceramics from marble sawdust had relatively excellent performance, when their flexural strength was 85.44 MPa at 1 180 ℃, with the water absorption rate 0.35%.