Using granite rejects to aid densification and improve mechanical properties of alumina bodies

The industrial use of waste materials in the ceramic industry has been widely investigated. This work describes the research carried out on the manufacturing of alumina bodies with granite reject additions. The reject was used as produced by a local industry that saws granite stones into blocks and slabs. This industrial process produces a significant amount of that reject, which is discarded in sedimentation lagoons, landfill areas or simply thrown in rivers, resulting in environmental pollution. Alumina and the granite reject were ball-mill mixed with 5 wt% manganese oxide and pressed under an uniaxial load of 20 MPa. Samples were subjected to thermal analysis (DTA, TG and dilatometry) and sintered in air at 1300 and 1350^∘C during 1 h in an electric furnace. Sintered specimens were characterized by X-ray diffraction, apparent density, open porosity and flexural strength. The results showed that the addition of granite reject and manganese oxide enables low temperature sintering and remarkably improves (~300%) the cold mechanical properties of the alumina body.