Investigations on the properties of Al2O3-MgO refractory castables bonded by in situ carbon containing calcium aluminate cement

In this paper, the properties including strengths, oxidation resistance, as well as corrosion resistance of Al2O3-MgO refractory castables bonded with Secar71, carbon back/Secar71 (S71CB) composite powders, in situ carbon containing calcium aluminate cement (CCAC), respectively, were investigated. The results shown that the cold crushing strength (CCS) and cold modulus of rupture (CMOR) of all the samples after sintered at 1000 degrees C for 3 h were higher than those of the samples after fired at 110 degrees C for 24 h due to the formation of ceramic bonds in the castables; And the CCS value of the castables bonded with Secar71 (T1) was higher than that of the castables bonded with S71CB (T2), CCAC(T3), respectively, due to its lower apparent porosity (AP). After sintered at 1600 degrees C, the CCS and CMOR of the samples of T2, T3 were reduced because of the increase of AP and appearance of more microcracks in the samples due to the expansion raised from the formation of CaAl12O19 and MgAl2O4. The carbons incorporated into the Al2O3-MgO refractory castables through CCAC as binders have excellent oxidation resistance, and were uniformly distributed in the matrix, and optimize structures of the matrix. Therefore, more residual carbons would be existed in the T3 sample at high temperature, resulting in improvement of the corrosion resistance of the Al2O3-MgO refractory castables.