Microstructure and Properties of Insitu Spinel Refractory Castable Containing ZrSiO4

Castable refractories are widely used in sever conditions at high temperature and pressure applications such as Petro Chemical process, industrial furnaces and specially in iron and steel industries. Attemps were made to improve the quality of the refractory castables by reducing cement content and/or by using different additives. In the present study the influence of zircon addition on phase analysis, microstructure and properties of ultra low cement in situ spinel castable refractory has been studied. Materials such as tabular alumina as the aggrigate, reactive alumina, deadburn magnesia, and micro silica as the fillers, and zircon as additive were used in this research. In situ spinel formation and influence of zircon addition on the phase developments were investigated by XRD analysis. Samples fired at 1400 ºC and 1600 ºC for 2 hours. Results showed improved physical and mechanical properties by addition of 2, 4, 6%, Zircon to the samples. Results also showed zircon decomposition has started at about 1400ºC and completed at 1600 ºC, resulting a reaction between zircon and alumina to form ZrO2 and alomiosilicate(Kyanite) composite in the matrix of the refractory castable samples. Finally in the samples fired at 1600°C extremely high cold crush strength (above 12 MPa) was detected which may be related to the spinel and kyanite formation in the matrix.