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 of mullite-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.