Low-cost northern Tunisian kaolinitic clay-based refractory materials and effect of a rich alumina clay addition

The addition of various quantities of raw materials could be used in order to improve the physical and pyroscopic performances of silica-alumina refractories manufacturing. Here we study the possibility of local kaolinitic clay (SB) valorization in low alumina fireclay refractory materials manufacturing. Alumina-rich commercial kaolin (AS) (33.4% alumina) was also used as an additive to (SB) clay (24% alumina), to improve the physical and pyroscopic performances of the manufactured samples. The thermal behavior of (SB) clay was studied to determine necessary parameters for the production of good chamotte. In order to elaborate the refractory samples, two mixtures were optimized; mixture M1 (80 wt.% of chamotte (SB) and 20 wt.% of (SB) clay as a binder in crude fine form) and mixture M2 (80 wt.% of chamotte (SB) and 20 wt.% of (AS) kaolin as a binder in crude fine form) and sintered at 1350 °C for 2 h after compaction and molding. The obtained samples were characterized by their bulk density, open porosity, shrinkage, cold crushing strength, microstructure by scanning electron microscope (SEM) micrographs, mineralogical composition, and their refractoriness under load. Our data suggest that the addition of the alumina-rich clay to the main mixture enhances the refractoriness from 1198 to 1213 °C (T0.5), the mechanical behavior of the manufactured pellets from 36 to 44 MPa, and the mullite amount from 25 to 29%, and decreases the open porosity from 19.6 to 18.6 %.