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Earth Sciences at the University of Fribourg

Bern-Fribourg Master in Earth Sciences

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Details of Master Thesis Topic (Module D):
Alkali-aggregate reaction (AAR) and cracking mechanisms of concrete structures (applied research project)

Master Thesis title: Alkali-aggregate reaction (AAR) and cracking mechanisms of concrete structures (applied research project)
Description:Alteration of concrete results in severe damage of buildings, as can be seen on a daily base entering our institute. In this context, cracking of concrete structures by alkali-aggregate reaction (AAR) is based on formation of expansive alkali-silica gels and associated alteration products. Although it is known that the related volume expansion induces crack formation, the effective processes and associated crack and alteration propagation are still a matter of debate, especially regarding different mechanisms of cracking. A current case study in a concrete material with different reaction fronts implies interference of several cracking mechanisms. The suggested MSc topic will therefore unravel which cracking mechanisms occur prior to AAR, concomitant to AAR, or are following the chemical alteration. Special emphasis will be paid to the role of freeze-thaw cycles since they may accelerate the deterioration.

These questions of this applied innovative research project should be targeted by macroscopic mapping (where useful by the means of drone technology) of real concrete structures, sampling of key structures in the mapped concrete areas allowing in a next step quantitative microscopic analyses. With this respect microscopic petrography of the aggregates, mapping of mineral reaction fronts and micro-cracking systems will be combined using polarizing light and scanning electron microscopy analytical techniques. The Master study is part of a collaboration of the Institute of Sciences of University of Bern with a Swiss Testing Laboratory specialized on the study of concrete materials.

Based on the outcome of the project, firstly the analytical procedure of AAR-damaged concrete structures can be optimized, and secondly the repair measures can be improved. This will, on the one hand, strengthen the expertise and market position of the industry partner and, on the other hand, increase the durability and economic efficiency of structural repairs. The project will be conducted with colleagues from the applied materials science industry (e.g. Dr. R. Zurbriggen).
Advisors:Prof. Marco Herwegh, Prof. Alfons Berger
Specialities:ERG, GEOL
University: BE

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