In situ coagulation of high-alumina zero-cement refractory castables

Coagulation methods originally developed for colloidal processing were investigated in this paper as alternative approaches to consolidate high-alumina refractory castables free of hydraulic binders (zero-cement). Three in situ reactions based on the direct coagulation casting (DCC) technique were evaluated to promote castable coagulation: (1) the autocatalytic hydrolysis of gluconic acid lactone, (2) the gradual dissolution of hydroxyaluminum diacetate particles in water, and (3) the enzyme-catalyzed hydrolysis of urea. The coagulating behavior of castables; and matrix-representative suspensions was investigated with the help of zeta potential analysis, pH measurements, castable free-flow evaluation, and oscillatory rheological tests. The enzyme-catalyzed hydrolysis of urea seemed to be the most appropriate mechanism to promote the coagulation of initially self-flow zero-cement refractory compositions.