Evaluation of recycled garnet and aluminum-oxides particles in preparation of refractory cement: thermo-physical performance

This manuscript investigated the use of discarded industrial abrasives (garnet and Al2O3-particles) for the manufacture of geopolymer-matrix composites. The discarded industrial abrasives were incorporated in 5, 10, and 20 wt% in geopolymer pastes, and their performance was evaluated both at room temperature and after being exposed to 1200 °C. The compressive strength, modulus of rupture, microhardness, density, porosity, and microstructure by SEM and XRD were studied. The results showed that the microstructure of the geopolymer paste is reorganized after exposure to 1200 °C, the geopolymers lose amorphous phase and new crystalline phases such as leucite and kalsilite are formed, which cause a good mechanical performance reaching up to 65 MPa of compressive strength. At room temperature in geopolymer composites with the incorporation of wastes-particle, the compressive strength was not affected. However, after exposure to 1200 °C, there was a loss in the mechanical strength with maximum values of 20 MPa for 20%-Al2O3 composite and 55 MPa for 5%-garnet composite. The microstructure analysis reveals cracking and porosity in composites by thermal treatment. The high porosity and cracking generated by thermal processes mean that its flexural strength does not exceed 7 MPa.