Effects of Changing the Specific Surface Area in the Ceramic Matrix of CAC-Containing Refractory Castables on the Initial Stiffening and Setting Behaviour

Abstract

Besides the coarse and medium grain size distribution, the matrix components play a central role in the performance of refractory castables. Practical experience shows that the particle size distribution (PSD) and the specific surface area of the ceramic matrix significantly influence processing, setting, and sintering behaviour. However, there is a lack of systematic studies on how PSD or specific surface area changes affect castable properties. This study aims to address this gap by varying ceramic matrices to create refractory model castables with different matrix surface areas. Three dispersing agents with different mechanisms (electrosteric and steric) were used at graded concentrations. Results show that castables with higher specific surface areas (using (very) finely ground and highly sintered alumina raw materials with high specific surface areas) and different dispersing agents and their concentrations show substantial differences in the initial stiffening and setting behaviour. Higher specific surface areas of the matrix result in an earlier first stiffening, while adding more dispersing agents leads to delayed stiffening. The refractory model castables’ first stiffening and hydration range (with a simultaneous temperature maximum) vary considerably depending on the dispersing agent used and its concentration, caused by completely different mechanisms.

Keywords

Refractory castables / Specific surface area / Dispersing agents / Initial stiffening / Setting behaviour

Author Contributions

Conceptualization, F.H., T.W., J.K., C.D., O.K.; Methodology, F.H.; Validation, F.H., T.W., J.K.; Investigation, F.H.; Data Curation, F.H.; Writing—Original Draft Preparation, F.H.; Writing—Review & Editing, F.H., J.K., T.W.; Supervision, J.K., C.D., O.K.

Ethics Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The datasets generated and analyzed during the current study are available from the corresponding author on reasonable request.

Funding

This research project (IGF-No. 22499N) is being funded by the German Ministry of Economic Affairs and Climate Action (BMWK) according to a decision of the German Bundestag.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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