Influence Mechanism of Binders on Semi-Lightweight Spherical Mullite Refractory Castables

Spherical aggregates have attracted much attention in the production of refractories due to their good fluidity, particle size controllability and close packing properties, and obtaining lightweight and high-strength spherical aggregates is the development focus of the thermal insulation refractory industry. In this work, semi-lightweight mullite spherical materials are used as major aggregate to prepare refractory castables. And the effects of Secar71 cement, Guangxi white clay, silica sol and cement-silica sol binders on the castables’ cold strength, thermal conductivity and thermal shock stability were investigated. The research results show that the castable prepared with cement silica sol as composite binder has excellent comprehensive properties, i.e. the CCS and MOR of the castable are 93.6 MPa and 17.93MPa respectively, the thermal conductivity at 900 ℃ is 0.678 W / (m·K), and the strength retention after thermal shock test is 43%. It is due to the addition of silica sol, which promotes the early hydration of cement and inhibits its later hydration, making the structure of castable more compact and the content of mullite higher.