Castables with similar flow values may display distinct rheological behaviors ranging from pseudoplastic to dilatant. Therefore, rheological characterization is necessary to design pumpable castables. Pumping of refractory castables is a technique that has been applied successfully in places that have difficult access or that are far from the mixer. This is possible because of high placing velocity and minimal material loss. In this process, special pumps push the material through pipes at high flow rates directly from the mixer to the molds. However, pumping refractory castables is a complex process because of the wide particle-size distribution (0.1-8000 μm) of these dense materials, which exhibit forces of distinct natures in the matrix (small particles + water) and in the aggregates (large particles).
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