Alumina monolithic refractories are utilized for ladle in steel industries. Alumina cement is an important raw material of monolithic refractories as a binder. CaO in the cement reacted with Al2O3 to form CaO-6Al2O3 （CA6） at high temperatures. CA6 shows grain growth with large anisotropy leading to volume expansion of the refractories upon sintering. However, the influence of CA6 on mechanical properties of monolithic refractories hasn't been investigated yet. In the present study, effective fracture energy γeff of monolithic refractories containing CA6 was examined from the point of view of CA6 formation and microstructures. The result showed that γeff enhanced with the increasing of sintering temperature. Higher sintering temperature caused CA6 grain growth which led to the deflection of crack along large crystals. Therefore, much energy was consumed for crack propagation. So, the estimation of the undulation of fractured surface confirmed this results that samples with rougher fractured surface gave higher γeff.

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