Refractory castables in the Al2O3-SiC-C system have been used mainly as linings for blast furnace runners. The association of these raw materials has enabled the development of high quality refractory castables due to improvements on their resistance to thermal shock, slag and metal corrosion. Nevertheless, the scientific knowledge regarding particle dispersion in this system is quite limited. In this work, representative suspensions of the matrix of Al2O3-SiC-C refractory castables were prepared in order to evaluate the efficiency of additives on the dispersion state of different raw materials and analyze the matrix rheological behavior as a function of pH and additive content. The polyacrylic and citric acids and a non-ionic surfactant were utilized as dispersants. The apparent viscosity and yield stress data obtained from the suspension rheological evaluation were used to elaborate matrix stability maps. Initial pH and flowability results for castables with different additive contents revealed that initial pH conditions were not coincident with the optimum dispersing region established by the stability maps. A shift of the castable pH value towards the optimum dispersing region was shown to be an effective approach to increase castable flowability.
rheological; refractory castables; thermal shock
