The impact of pre-formed and in situ spinel formation on the physical properties of cement-bonded high alumina refractory castables

Abstract Alumina–magnesia and alumina–spinel castables present some unique characteristics. Whereas the in situ spinel (MgAl 2 O 4 ) formation provides an enhanced corrosion and thermal-shock resistance to the castable, the composition with pre-formed grains shows higher volumetric stability and do not have the inherent MgO hydration problems. As these distinct ways of spinel incorporation result in particular properties to the refractory material, a castable containing both in situ and pre-formed spinel might present balanced properties and a suitable performance in steel ladle applications. Considering these aspects, cement-bonded high alumina castables containing both pre-formed and in situ spinel were developed and evaluated by means of assisted sintering tests, microstructural analyses, thermodynamics simulation and mechanical and thermal-mechanical properties evaluation. The CA 6 formation presented different features according to the content of in situ spinel generation in the matrix, which affected the castable properties. Additionally, compositions containing both in situ and pre-formed spinel seemed to be a feasible way of attaining a designed linear dimensional change without affecting the spinel and CA 6 contents.