Study On Properties Of Andalusite-based Low-cement Refractory Castables

Andalusite-based low-cement castable is main objective of this study. In first stage, the impacts of two types of andalusite with different source and chemical composition on castable properties were investigated. Same time, under same formulation conditions as particle size distribution, additive and aggregate types, via replacement of andalusite by tabular alumina powders in certain level, detailed study was made on installation, mechanical and thermal properties of castable. Furthermore, analysis and comparisons were presented in this paper between andalusite-based and fused-mullite-based low-cement castables. After systemic studies, the conclusions could be drawn as below:Two types of andalusites used in this study do not bring significant impact on low-cement constable's installation properties. Comparing with Fused-mullite-based castable, it seems that andalusite-based castable takes the advantage in water demand and cold mechanical strength. When tabular alumina powders are introduced into the matrix to replace andalusite powder, castable shows lower water-demand and higher cold mechanical strength following the increase of tabular alumina powder dosage. In this study, 3 main factors are found to influence the thermal properties of andalusite-based low-cement castable. Those main factors are liquid phase quantity, mullitization process and mullite forming extent (mullite phase quantity).Andalusite-based castable does not show much advanced properties than fused-mullite-based castable before mullitization process starting as there is no formation of mullite phase in the matrix. Once the temperature goes over 1300C,the self-mullitization of andalusite might promote the bulk expansion and sintering process of matrix. Consequently, better thermal properties can be seen in andalusite-based castable comparing with mullite-based castable, such as mechanical strength after firing, thermal module of rupture, refractoriness under loading and thermal creep.When the dosage of tabular alumina powder is about 10wt%, it could not bring positive impact on matrix purities, but also increase bulk stabilization and other thermal mechanical properties of castable during the thermal mullitization process.