China's Refractories

Abstract: Improving the green mechanical strength and thermal shock resistance of silica sol-bonded corundum castables is of great significance for promoting their large-scale application. Silica sol-bonded corundum castables were prepared using brown corundum, dense corundum powder, α-Al₂O₃ micropowder and SiO₂ micropowder as the main raw materials, and silica sol as the binder. The effects of different additions of chopped glass fibers (0, 0.2%, 0.4%, 0.6%, 0.8% and 1%, by mass) on the properties of the castables were studied. The results show that with the increase of the fiber addition, the cold modulus of rupture, cold compressive strength and hot modulus of rupture of the samples first increase and then decrease. After drying at 110 °C, the sample containing 0.4% fibers has the cold modulus of rupture of 9.1 MPa and cold compressive strength of 27.4 MPa, increasing by 80.4% and 41.2%, respectively, compared with the one without fiber addition. This is because the fibers bonded with the silica sol-gel interface to form a stressed skeleton, strengthening the bonding between the matrix and the aggregates. When subjected to external stress, the fibers can effectively share the load and prevent crack propagation, thus increasing the strength. In addition, the sample with 0.4% fibers has the highest cold modulus of rupture before and after thermal shock, and its strength retention ratio increases by 16.1% compared to the sample without fibers. Overall, the sample with 0.4% fibers exhibits the best comprehensive performance.

Key words: corundum castables, silica sol, glass fibers, mechanical properties