Reduction of CO2-emissions by production of highly reactive belite cement
Final Report Abstract
The aim of the DFG-funded project was to develop and investigate highly reactive belite phases. The performance of the corresponding belite phases was to be tested in concrete. In a first phase, highly reactive belite phases were produced in a two-step process (autoclave treatment at 200 °C, burning at approx. 450 °C) and extensively characterised. The corresponding phases x-C2S and amorphous C2S are extremely reactive and show degrees of conversion of 90 % after a few days. Subsequently, it was investigated whether these belite phases can also be produced in the usual hightemperature process. The thermodynamic considerations and the extensive synthesis experiments showed that it is not possible to produce these phases in the high-temperature range. In the next phase of the project, it was investigated how the low reactive belite phases from the usual high-temperature process in the cement industry can be transformed into reactive phases. Successful investigations were carried out in the areas of foreign ion incorporation (lithium, sulphur), rapid cooling and reaction grinding. The produced belite showed a very high reaction rate in all three cases. A decisive factor for the high reactivity is a high solubility of the phases in the pore solution. This high solubility leads to supersaturations with respect to the reaction product C-S-H, which are significantly higher than the supersaturations in the reaction of the low reactive modifications and which allow nucleation and growth of C-S-H. In a further step, a kinetic model for belite phases was established on the basis of these findings and further basic investigations, with the help of which the reactivity of the phases can be modelled. In the final section of the project, concretes produced with the highly reactive belite phases from the two-stage process were characterised in terms of fresh concrete and hardened concrete properties. The focus was on durability investigations. A concrete based on a Portland cement was used as a reference concrete. The investigations showed that, despite an almost identical strength development, differences occurred in the area of durability. The reasons for this must be clarified in further investigations.
Publications
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Entwicklung und Untersuchung von alternativen Dicalciumsilikat-Bindern auf der Basis von α-C2SH. Dissertation, Bauhaus Universität Weimar, 2017
T. Link
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Produktion und Charakterisierung von Niedrigtemperatur Belitbindern (LTBB). Tagungsband der 20. ibausil, Weimar, 2018
B. Kraft, T. Link, F. Bellmann, M. Ben Haha, H.-M. Ludwig
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Untersuchung zur Kinetik der Belithydratation. Tagungsband der 20. ibausil, Weimar, 2018
A. Isserstedt-Trinke, F. Bellmann, T. Stanek, T. Link, H.-M. Ludwig
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Early hydration of C2S doped with combination of S and Li. SN Applied Sciences (2020) 2:429
M. Boháč, T. Staněk, A. Rybová, A. Zezulová, F. Bellmann, H.‑M. Ludwig
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Thermodynamic data of belite polymorphs. Cement and Concrete research, Volume 152 (2022) 106621
K.-D. Grevel, F. Bellmann, J. Majzlan, E. Dachs, A. Benisek, H.-M. Ludwig
