Practical experience shows that the particle size distribution (PSD) and the specific surface area (SSA) of their ceramic matrix significantly influence the processing, setting and sintering properties of refractory castables. However, there is a lack of knowledge about the extent to which the properties of refractory castables are influenced by changes in the SSA and the PSA of the matrix of refractory castables. A better understanding of this influence promises considerable new potential for innovative refractory castables.
The zeta-potential of suspensions of matrix particles (< 45 µm) was measured, depending on the matrix’ SSA and the dispersing system used. Castables based on the analysed matrices were mixed and investigated. Two dispersing systems were used in the refractory castables with different amounts of the dispersing agent.
Results reveal the influence on deflocculation and the first stiffening of the corresponding castables. Using polycarboxylate ether (PCE) as dispersing agent, with increasing amount of the PCE the time until stiffening is elongated distinctly. The same effect occurs when the SSA of the matrix is being decreased while the amount of dispersing agent remains constant. A correlation between the moment of stiffening and the amount of dispersing agent per surface area can be shown.
Using a polymethacrylate (PMA) in combination with citric acid as dispersing agent, both an increase in the amounts of PMA and citric acid lead to a longer time until stiffening. The role of the SSA of the matrix is not completely clear here.