Dry-pressing preparation of mullite columnar structure using waste gangue during firing and its properties

The mullite columnar structure are prepared by a dry-press method using waste gangue substituted for kaolin clay. The properties e.g., water absorption, bulk density and bending strength of the samples fired at the temperature range of 1300–1550°C are studied. The microstructure of mullite columnar structures are characterized by X-ray diffraction and field emission scanning electron microscopy with an energy dispersive X-ray spectroscopy. The results reveal that waste gangue substituted for the kaolin is available for mullite columnar structure. Impurities in waste gangue e.g., TiO2 and Fe2O3 lower the formation temperature of mullite columnar structure, which endow the samples with high refractoriness. Due to the presence of interlocking structure constructed by mullite crystals, the sample achieves the optimum bending strength of 97.6 MPa at the temperature of 1400°C, which is future application in refractory materials. The dry-pressed preparation method provides a simple way to synthesize mullite columnar structure using waste gangue substituted for kaolin clay that can be future applied in lightweight refractory industry.