Agentes ligantes e seus efeitos em concretos refratários alumina-magnésia

the usual binder of alumina-magnesia castables is the calcium aluminate cement. due to in-situ spinel (mgal2o4) formation at high temperatures, these materials present an expansive behavior. when bonded with cement, further reactions (ca2 and ca6 formation) also contribute to the overall expansion. changing the most common cement used (~ 30 wt.% cao) for other containing less calcia (~ 20 wt.% cao) or for hydratable alumina are suitable alternatives for controlling the castables' volumetric stability. nevertheless, the binder replacement may affect castables properties, such as cold mechanical strength, mgo hydration degree and properties during and after sintering. therefore, the objective of the present paper is to analyze the effects of these binders on the alumina-magnesia castables processing. as a result, the binder systems can be used as a tool for designing the alumina-magnesia castables expansion, increasing the flexibility on the selection of steel ladles linings.