There is a great relationship between the fluidity of the unshaped castable and the proportion of the castable trace agent and the material selection, it’s not significant with the ratio of the aggregate. In general, the fluidity of the castable should be considered from the properties of itself first, which is divided into acid, neutral ,alkaline, weak acid, weak alkali and so on. It can greatly improved the fluidity of the castable if add a certain amount of silica fume reduce using amount of the cement and greatly increase strength of the castable, but we all know that most of the silica fume is used as industrial secondary product, because of the quality stablity is not good,it may affect the overall usability of the castable.