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COllective Research NETworking
Narodowe Centrum Badań i Rozwoju
Stowarzyszenie Producentów Materiałów Ogniotrwałych




As part of the 29th CORNET call, the project „RefraPredict: „Predictaibility of long-term
refractoriness of refractory high alumina monolithics under high thermal load with special regard
to impurities introduced by secondary raw materials” was approved for implementation and the
Association of Refractory Materials Manufacturers obtained its funding from the National Centre for
Research and Development (NCBiR). The partners are Forschungsgemeinschaft Feuerfest e.V.,
(project coordinator) Hochschule Koblenz, (contractor) and the Polish Research Network Łukasiewicz
– Institute of Ceramics and Building Materials O/Refractory Materials, Poland (research contractor).
Completion date 1.01.2021 – 31.12.2022.

General assumptions of the project

Due to the depletion of natural resources, there is a need to increasingly use recycled raw materials.
For refractory materials, used in various industries, the use of materials after work as secondary raw
materials is not simple. The material after service usually contains admixtures, which even with a
small share significantly reduce the refractory parameters of materials. Therefore, the project
provides for comprehensive research, determining the impact of the presence of the most common
impurities (Na, Si, Fe, Ca, Ti) in potential secondary raw materials on the quantities characterizing
refractory materials (e.g. refractory under load, creep, thermal shock resistance, mechanical
strength, elastic properties, work of fracture). The obtained values will be analyzed in comparison
with the results of microstructure, chemical composition, phase composition, porosity and density.
Particular attention will also be paid to research on the influence of admixtures on the temperature
of transition of the material from a brittle to a plastic state and to investigate the influence of
admixtures on the mechanism of creep of monolithic material. Lowering the transition temperature
to the plastic state usually means a deterioration of high-temperature immune properties, but it can
improve the material’s resistance to cyclic temperature changes, i.e. thermal shock. Determination in
the project which factors during the production of materials with the participation of secondary raw
materials have a greater impact on the refractory parameters, and which on the temperature of
transition to the plastic state and creep will be important in the design of the desired properties of
refractory materials using recyclable materials. They will also be important when choosing materials
for specific industrial applications (depending on thermal conditions and their stability). Test material
for testing the possibility of conscious property formation high-temperature monolithic materials by
introducing secondary raw materials containing impurities of specific mutual proportions into them,
will be in the project corundum and corundum-spinel castables on a sol-gel bond not containing
silica. The tests will be carried out in terms of clarifying the criteria determining the maximum
operating temperature of refractory material and searching for indicators on the basis of which, at
the stage of laboratory tests, it will be possible to predict long-term changes in the
thermomechanical properties of materials under operating conditions.

Scope of research

Opening meeting

On 28.01.2021, an on-line meeting was held to open the implementation of the RefraPredict project
The meeting was attended by research teams from Germany: FGF and Hochschule Koblenz and
Polish Ł-ICIMB as well as representatives of industry and coordinators from the German and Polish

After introducing and characterizing the aim of the project, the representatives of the individual
teams presented the envisaged scope of research:

  1. L. Erbar, K.Sarnow (HS Koblenz) – Development of model refractory castables with a systematically contaminated matrix using prepared “precursors” and study of the impact of impurities on the properties of castables “in the cold”;
  2. E.Brochen – Development of an innovative device enabling simultaneous study of the influence of temperature gradient and mechanical load and testing of the properties of high-temperature model castables;
  3. J.Backyard (Ł-ICIMB) – Development of a method of creep velocity testing based on Norton-Bailey concept and study of the microstructure and properties of model castables. In the discussion, a lot of space was devoted to the preparation of model castables.

2nd meeting of project implementers and users 6.07.2021 (on-line)

The results of the research from the period from 01.2021 to 06.2021 and the expected next actions for the period from July to the end of December 2021 were presented.

  1. Laura Erbar, Katharina Sarnow (Hochschule Koblenz): – Development and production of reference material; – Introduction of critical impurities in refractory raw materials with a high content of alumina – preparation of precursors
  2. Jacek Podwórny, Robert Kusiorowski (Łukasiewicz – ICiMB): – Thermochemical simulations (FactSage) to identify a critical combination of impurities: – Examination of the maximum operating temperature (“refractory”) of reference castables – strategy of testing.
  3. Erwan Brochen (FGF): – Study of the combined effect of thermal gradient and mechanical load on refractory castables; – Thermomechanical characteristics of reference castable.

3rd meeting of project implementers with users on June 19, 2022

The meeting took place in Wisła during the 19th International Conference: “Refractory materials: production, test methods, application“. During the meeting, the progress of the work was discussed in turn by:

1. L.Ebar (Hochschule Koblenz) discussed the preparation of 5 types of impurity precursors and the results of testing the “cold” properties of prepared alumina concretes. She drew attention to the problems encountered in the preparation of synthesized impurity additives. Their high degree of sintering, and often melting, caused difficulties with grinding and grinding to the grain size ensuring uniform dispersion of impurity precursors in the matrix of prepared alumina concrete samples. This resulted in a delay in the delivery of samples for further testing.

2. J.Podwórny (Łukasiewicz ICIMB OMO) presented the results of thermomechanical tests of reference samples.

3. E.Brochen (FGF) presented the construction of a prototype device for testing the behavior of refractory materials subjected to simultaneous stresses resulting from the temperature gradient and mechanical loads.



Dissemination – conferences 2022

1. Jerzy Czechowski: The refractory industry in the EU – in the current state and in the perspective of future expectations – Conference “Ceramics in Europe 2022”, combined with 9ICC (International Congress on Ceramics), XVII ECerS Congress and Electroceramics XVIII. presented at the 9ICC session; Kraków 10 – 14.07.2022 (presented, among others, the impact on the environment and the RefraPredict project).



J. Podwórny, O. Krause, E. Brochen, K. Dudek, R. Kusiorowski, M. Kujawa, L. Erbar, K. Sarnov: Improvement of sinterability of alumina concrete matrix by highly reactive alumina addition. – International Colloquium on Refractories ICR® 2022, September 28-29, 2022, Aachen, Germany.




3rd meeting of project implementers with users on January 27,2023 (online)

The meeting started at 9:30 am and coordinator of the project E. Brochen welcomed all attendees and reminded them of the antitrust rules to be observed during the meeting. Than the representatives of the research teams presented the results:

  1. Presentation of the R&D results from Hochschule Koblenz/Germany

Katharina Sarnow started by reminding that Hochschule Koblenz focused its activities on the development of model-refractory castables with systematically impurified matrix and the investigation of the influence of the impurities on their “cold” properties. She described preapartion of precursors and model-refractory castables with systematically impurified matrix. Than presented Investigation of influence of the impurities on model-refractory castables “cold” properties. All high alumina cement-free model refractory castables displayed comparable flow and working properties.  The CMOR after drying at 110 °C of the reference castable (without spinel precursors and impurified raw materials) was found to be slightly higher than for the castables with impurified raw mate-rials, but no striking correlation between kind of impurities and the decrease of the CMOR appeared. The addition of spinel precursors led to an increase in the CMOR, especially for castables with impurified raw materials, but again but obvious correlation between kind of impurities and the increase of the CMOR.

  1. Presentation of the R&D results from L-ICiMB/Poland.

Jacek Podwórny began by recalling that L-ICiMB was engaged in an extensive characterisation of the castables developed by Hochschule Koblenz, including mineralogical, microstructural and thermomechanical investigations. He referred more broadly to:

  • Refractoriness under Load (RuL): test pieces already sintered above 1650 °C display a much higher RuL (T0,5 > 1700 °C) than test pieces that only got “dried” at 450 °C (T0,5 > 1420 °C). The use of spiked precursors led to a decrease of the T0,5 up to 60 °C.
  • Resonant Frequency & Damping Analyse (RFDA): the dehydration of the hydrate phases above 500 °C led to massive decrease of the stiffness of the test piece, at least up to circa 1000 °C, then the sintering process (starting at about 1000 °C) promotes an increase in the stiffness that is retained during cooling. In parallel, the damping remains quite stabile up to 700 °C, then increased rather steadily up to 1200 °C while the uncertainty on the measure rose drastically, especially around 1100 °C. This might have to do with the brittle-to-ductile transition of the material. The addition of impurities to the castable almost did not significantly impact the previous observations.
  • Creep in Compression (CiC): After a short reminder of the three creep stages for a given temperature according to Norton-Bailey (I: decelerating creep rate, II: constant creep rate, III accelerating creep rate up to failure) and the creep promoting influence of temperature and applied stress, Jacek Podwórny explained that in order to increase the applied stress, while using a standard testing system, the external diameter of the test piece, and accordingly their wall thickness have to be decreased. As expected, the higher the applied apparent stress and/or testing temperature, the more intense the creep rates (though stage III has not yet been observed). The use of spinel forming additives enhanced the creep resistance, while impurities, not surprisingly, seems to reduce it.

  1. Presentation of the R&D results from Forschungsgemeinschaft Feuerfest/Germany.

FGF develops a system able to investigate the combined effect of temperature gradient and mechanical load in order to simulate a thermomechanical loading in test pieces similar to what refractory materials are subjected to as a part of a complete lining in service.

A first test demonstrated that impending the free thermal expansion thermal of the test piece near to the hot face (reference castable) heated to 1200 °C led to stress levels of almost 20 MPa in both directions at the end of the heating. In the next series of tests, a constant loading was applied and the dimensional change of the test piece monitored. In comparison to a baseline measurement with limited loading in both directions (0,15 MPa), the increase of the load in one direction (10 MPa, 20 MPa and 30 MPa) impeded the free thermal expansion (in the loaded direction) at elevated temperature. The difference in the displacement of the refractory dies in the two perpendicular directions (“creep”) increase with increasing loading.

In parallel, the FGF performed supporting investigations to assist the Ł-ICiMB. Thanks to wedge splitting tests (WST), the stabile fracture process of test pieces is monitored and quantified, hence assessing the ability of the castable to resist damaging. The reference castable (high alumina cement-free model refractory castables) display a relative moderate strength and specific fracture energy that get weakened by increasing temperature. The addition of spinel precursors to the castable promote an increase of the material strength and specific fracture energy as well as reduction of its brittleness.

The addition of impurities to the castable almost systematically resulted in the deterioration of their mechanical properties and enhancement of their brittleness. One notable exception is the combination of Fe and Ca that apparently toughen the material and reduce its brittleness, which corelates with the combination of impurities that is expected to form the lowest amount of liquid at the testing temperature.

  1. Discussions

The discussion drew attention to the reason for the observed differences in ultrasonic measurements, differences in creep in compression tests and the explosiveness of spinel forming free cement castables containing spiked raw materials.

5-th meeting of project implementers with users on May 17 2023

  On May 17, 2023 (i.e. after the completion of the part financed by the National Center for Research and Development), the project manager, Dr. Erwan Brochen, organized the 5th meeting with the Users. At the request of the manager of the Polish part of the project, the meeting had a hybrid character and was attended on-line by representatives of two national Users and the project manager. Representatives of the team of implementers from Łukasiewicz-ICIMB CMO also participated online. The meeting presented:

• E. Brochen (FGF) – “Introduction to the project”

• L.Ebar, K.Sarnow (Hochschule Koblenz) – “Introduction of critical impurities in refractory high alumina raw materials – preparation of precursors” and “Production and characterization of the reference material”

• J. Podwórny (Łukasiewicz-ICIMB) – “Investigation of the maximum service temperature (“refractoriness”) of the reference castables – setting up a testing strategy”.

• E. Brochen (FGF) – “Investigation of the combined effect of thermal gradient and mechanical load on refractory castables – development of a new testing method” and “Thermomechanical and thermochemical characterization of the reference castables”.

After the presentation, a discussion on the obtained results and suggestions of industrial partners regarding further research directions took place.



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