The continuous evolution in the installation techniques of refractory castables (self-flowing, pumpable, shotcrete, etc.) has intensified the requirements for optimization and control of the rheological behavior of such materials. The main factors that control the rheology of castables are the particle size distribution, the solid concentration, and the nature of the raw-materials and chemical additives present in the system. Therefore, the right choice of dispersing agents is very important for the systematic development of these materials. However, the selection is traditionally based on castables' free-flow or matrix rheology measurements, which do not evaluate the material's behavior during the distinct steps of its production and application. In this study, a novel method based on the rheometry of castables is proposed for the evaluation and selection of dispersants. Unlike usual techniques, the present one allows the evaluation of the rheological behavior from the mixing step until the flow under intensive shearing. Additives usually applied in high alumina castables, sodium polymethacrylate and citric acid, and two dispersants based on a new molecular design were evaluated by the proposed method and by the traditional free-flow technique. Results demonstrated the advantages of the proposed characterization method and demonstrated the superiority of the novel additives.
castables; refractories; rheology; dispersants; rheometry
