03:00 pm
Refractory cements containing Zr and Sr as alternatives to the CACs designed for the production of high performance monolithic refractories
Prof. Dominika Madej | AGH University of Science and Technology in Kraków | Poland
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Author:
Prof. Dominika Madej | AGH University of Science and Technology in Kraków | Poland
The hydration process of calcium aluminate cement (CAC) in a cementitious system is crucial for development of the high-quality cement based monolithic refractories. An increasing tendency to use the monolithic refractories over the past decade have been accompanied with the parallel trend of the improvement of CAC-containing castables by introducing Zr-containing compounds, e.g. ZrSiO4, CaZrO3, ZrO2 or AZS and AZ materials. Furthermore, since CaAl2O4 and SrAl2O4 form a solid solution series, and since the replacement of Ca with Sr in CaZrO3 is also noted, the system of CaO-SrO-Al2O3-ZrO2 (C-Sr-A-Z) will form large group of hydraulic binders under the aegis of this project. Thus, in this study, composite cements belonging to the C-A-Z and C-Sr-A-Z systems were evaluated as alternatives to CACs for use in the refractory monolithic technologies, especially castables.
Complementary experiments of X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and time-resolved electrochemical impedance spectroscopy (TR-EIS) using the Impedance Camera were used to analyse the hydration process of state-of-the-art cement systems in the absence and presence of Zr and Sr. Some experiments with castables were also done.
ACKNOWLEDGEMENTS
This project was financed by the National Science Centre, Poland, project numbers 2017/26/D/ST8/00012 and 2022/46/E/ST5/00280 (Recipient: D. Madej). This work was also partially supported by the statutory funds of the Faculty of Materials Science and Ceramics, AGH University of Science and Technology, Kraków, no. 16.16.160.557.
03:20 pm
A new approach to achieve robust and easy to use NCC
Frederic Lacoue | IMERYS | France
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Authors:
Frederic Lacoue | IMERYS | France
Jean-Charles Alcoz | IMERYS | France
Quentin Collomb | IMERYS | France
Dr. Christoph Wöhrmeyer | IMERYS | France
Key drivers for the development of silica sol based No Cement Castables (NCC) over the last two decades are their fast drying ability coupled with the in-situ formation of an almost pure mullite matrix composition at high temperature. It then leads to a high refractoriness and thermal shock resistance. On the other hand, the main drawbacks of this solution compared to the largely used calcium aluminate bond, are the more difficult control of setting, lower green strength, and the need to transport and handle the liquid colloidal binder at the job site.
This study will demonstrate that calcium aluminate could as well be a suitable binder to formulate castables with equal or less than 0.2% CaO as required by the classification for NCC. This solution will not require a separate liquid colloidal binder and works simply with water and provides a similar robustness and formulation flexibility as traditional ultra low cement castables (ULCC).
A bauxite refractory castable formulation (ULCC/NCC) is used to compare different binders such as colloïdal silica, calcium aluminate SecarⓇ71, and a new calcium aluminate based NCC binder concept. For each binder, flow behavior, structuration kinetics, exothermic profiles and physical properties after curing and firing up to 1600°C are investigated. Hot properties such as refractoriness under load and hot modulus of rupture are also compared. X-ray diffraction is done on the matrix composition of the castables to quantify the degree of mullitization. Dry-out behavior is also compared through macro thermogravimetric analysis on 10x10x10cm cubes.
03:40 pm
What is really in there? Classification of aromatic compounds in carbon-based refractory bonds by high-resolution mass spectrometry and multivariate statistics
Dr. Ali Masoudi Alavi | Universität Koblenz | Germany
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Authors:
Julia Doll | Universität Koblenz | Germany
Dr. Ali Masoudi Alavi | Universität Koblenz | Germany
Prof. Dr. rer. nat. Dr. h.c. Peter Quirmbach | Universität Koblenz | Germany
Carbon is used in different configurations in refractory materials because of its property-enhancing effect. In this context, especially organic carbon is frequently criticized due to its partly carcinogenic and mutagenic impact on human health. But despite decades of research, there is still no standardized analytical strategy for the detailed investigation of the complex organic phases in refractory materials apart from the analysis of some single defined compounds. Therefore, in this work, a non-target analytical strategy for characterization and classifications of refractory materials is presented. This is particularly challenging because the organic phase in these materials is often present in only a very small proportion and along with many other substances, so that highly sophisticated analytical methods have to be used. The focus in this work is on the generation of a large amount of high-quality data using high resolution time-of-flight mass spectrometry as well as a targeted reduction, evaluation and interpretation of these data using multivariate statistical approaches. In addition to the detailed characterization of the materials based on their structure and chemical com-position, characteristic features of each sample could be identified and extracted to provide a comprehensive understanding of the investigated refractories in order to evaluate their quality and even foresee their behavior.