Determination of mechanical properties and thermal treatment behavior of alumina-based refractories

Two different types of alumina-based refractories have been investigated. Chamotte and bauxite were the raw materials, being molded using a system of aluminate cement and water or a phenol–formaldehyde resin, as binder. Different raw material's grain size, water content, molding pressure, and firing temperature were selected for the preparation of the specimens. The mechanical strength of all specimens was determined using compressive tests, where parameters with physical meaning, such as maximum stress, maximum strain, elasticity parameter, and viscoelastic parameter were obtained after modeling the collected stress–strain data. In addition, water quenching test was performed for both samples, in order to present their thermal stability and mechanical wear after certain cycles.Process conditions as well as the raw materials’ characteristics were correlated with the compressive properties. More specifically, maximum stress seemed to increase when increasing all parameters except grain size both for bauxite and chamotte samples. The increment of bonding phase, grain size, and molding pressure caused an increment in maximum strain for both types of refractories. However, the higher the firing temperature was the higher the maximum strain of bauxite appeared, while the maximum strain of chamotte samples was decreased. Modulus of elasticity seemed to increase with bonding phase content and firing temperature and decreased with grain size for both types of refractories. For bauxite samples higher molding pressure caused a decrement in elasticity parameter while for chamotte in caused an increment. As far as the quenching tests are concerned chamotte samples seemed to be more tolerant to thermal shock. After data acquisition, the change presented in elasticity parameter (E) was also modeled with the number of cycles. Both bauxite and chamotte samples showed a decrement in maximum stress after thermal treatment, while elasticity parameter seemed to have a more severe decrement for bauxite samples.