The invalidation reasons of Al2O3-SiC-C castable used in the iron runner of the blast furnace are analyzed in the paper.

The results show that the invalidation of castable is mainly related to the alumina cement. Besides, the existence of ultra volume Cl ions may affect the solidification of castable as well.

By adding a little amount of new calcium alumina cement, the strength of castable can be recovered and it has no bad effect after application.

In addition, the separate packaging of cement and castable can effectively reduce the strength loss of cement, and thus avoid the failure of castable. You’d better add cement when mixing.