Effect of Silica Sol Impregnated Recycled Aggregates of Spent Mullite–SiC Bricks on Performance ofAl2O3–SiC–C Castables

    For the improvement of the fluidity of castables with recycled aggregates of mullite SiC bricks due to their high porosity, high water absorption and massive cracks, silica sol was used to impregnate mullite–SiC brick aggregates. The effect of silica sol concentration on the aggregate properties ofmullite–SiC bricks was investigated. The microstructures and the element distributions of modified mullite–SiC bricks aggregate were analyzed by scanning electron microscopy coupled with energy dispersive spectroscopy. The water wettability of mullite–SiC brick aggregates was characterized via water contact angle measurement. The results show that after the impregnation of mullite–SiC brick aggregates, the water absorption of mullite–SiC brick aggregate reduces from 6.9% to 2.6%, and the water contact angle decreases from 55 ° to 7 °, thus improving the water wettability of the aggregate. The impregnated mullite–SiC bricks were used as recycled aggregates instead of brown corundum in Al2O3–SiC–C castables. In addition, the effect of aggregates on the properties of castables was also investigated. The results indicate that Al2O3–SiC–C refractory castables with silica sol concentration of 15% modified mullite–SiC bricks aggregates after heat-treated at 1 450 ℃ have the minimum apparent porosity of 17.1% and the maximum cold compressive strength of 73.7 MPa, which is 45.7% greater than the strength of castables with brown corundum as aggregates. Meanwhile, the residual strength and the residual strength ratio of castables after thermal shock are increased by 69.4% and 24.1%, respectively.