Effects of Changing the Specific Surface Area in the Ceramic Matrix of CAC-Containing Refractory Castables on the Rheology and Processing

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 (SSA) of the ceramic matrix significantly influence processing, setting, and sintering behaviour. However, there is a lack of systematic studies on how changes in PSD or SSA affect castable properties. This study aims to address this gap by varying ceramic matrices to create model refractory castables with different matrix surface areas. Three dispersing agents with different mechanisms (electrosteric and steric) were used at graded concentrations. Results show that the SSA of the ceramic matrix has a significant influence on the rheological behaviour of refractory castables. A low SSA leads to shear thickening behaviour, a (very) low relative yield stress, and a high slump-flow. Castables with an intermediate SSA and a multimodal composition show Bingham behaviour with a moderate relative yield stress and low relative viscosity, whereas a high SSA leads to shear thinning behaviour with a (very) high relative yield stress, (very) high relative viscosity, and a low slump-flow. Measurements of the dynamic viscosity of matrix suspensions at very low shear rates correlate with the rheological behaviour of fully composed refractory castables. Regression analysis using the Herschel-Bulkley model successfully captures the observed qualitative relationships.

Keywords

Refractory castables / Specific surface area / Dispersing agents / Rheology / Processing

Statement of the Use of Generative AI and AI-Assisted Technologies in the Writing Process

During the preparation of this manuscript, the authors used DeepL SE in order to enhance the linguistic quality. After using this tool, the authors reviewed and edited the content as needed and take full responsibility for the content of the published article.

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 analysed during the current study are available from the corresponding author on reasonable request.

Funding

This research project has been supported by the Federal Ministry for Economic Affairs and Energy (BMWE) on the basis of a decision by 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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