Selection of dispersants for high-alumina zero-cement refractory castables

This article reports on the evaluation of novel short-chain molecules to improve the dispersion of zero-cement high-alumina refractory castables. Two approaches were investigated to enhance the dispersing efficiency of short-chain compounds: (a) the increase of the density of dissociable sites per molecule and (b) the improvement of the adsorption ability of the molecule at the usual pH range of high-alumina castables. Gallic acid and 2-phosphonobutane-1,2,4-tricarboxylic acid were selected based on these requisites and evaluated as potential dispersants with the help of zeta potential analysis, rheological measurements and free-flow tests. Results indicate that such compounds are able to efficiently disperse zero-cement high-alumina castables, enabling a reduction of their water consumption for a given fluidity level.