China's Refractories

Abstract: Compared with traditional aggregates, spherical aggregates with high flowability, easy control of particle size distribution and favor of dense packing and so on, are expected to replace traditional aggregates as important raw materials for future high performance refractories. Therefore, investigation of effects of spherical aggregates addition on properties of refractories becomes very meaningful. Using A70 mullite traditional aggregates and A70 mullite spherical aggregates, bauxite homogenization powder, microsilica, and calcium aluminate cement as raw materials, different Al₂O₃-SiO₂ system low cement castables were prepared by replacing conventional aggregates with spherical aggregates. The effect of spherical aggregates addition on workability and mechanical properties of castables after heated at different temperatures was researched, and microstructure of the specimen was analyzed by SEM. Compared with traditional irregularly shaped aggregates, spherical aggregates endow castables with better flowability and easy pump ability. By introduction of spherical aggregates into the castables, flowability and pumpability are significantly improved, and water addition and ball completely sunk time are reduced.  The introduction of spherical aggregates is favorable to density and cold crushing strength of castables, but unfavorable to CMOR. The effect of spherical aggregates addition on HMOR at 1 400 ℃ can be negligible. Microstructure analysis shows that the boundary bonding between spherical aggregates and matrix is strong, similar to the traditional aggregates.

Key words: spherical aggregates, alumina silica system castables, mechanical properties