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B. Schubert:
"Studies on graded textile-reinforced concrete elements";
Supervisor: J. Kollegger, P. Preinstorfer; Institut für Tragkonstruktionen, 2021; final examination: 2021-06-18.

Climate change gives reason to rethink proven structures and to optimize them with regard to their environmental impact. With regard to the construction industry, especially the concrete sector, there is an urgent need to reduce these emissions through various measures due to the high greenhouse gas emissions generated during cement production. The innovative composite material textile concrete enables the production of slim and durable building components, as the non-metallic high-performance fibers do not need to be protected against corrosion and therefore do not require high concrete decks. By using this high-performance material, a considerable amount of concrete and thus cement can be saved, which is why this approach is included in this work as a solution strategy. Another approach to minimize cement and thus the harmful environmental effects of this building material is the use of specially developed, cement-reduced concretes - so-called eco-concretes - in the production of which cement is substituted by other additives such as fly ash or limestone powder. Particularly with regard to textile-reinforced components, there is great potential here, since the reinforcement does not have to be protected against corrosion by the alkaline environment in the concrete and therefore larger quantities of cement can be replaced by additives without endangering durability. The aim of this work is to use these solutions to create a structural component made of textile concrete which, despite its smaller cubature and reduced cement content compared to conventional reinforced concrete, has a high level of performance.In the course of this scientific work, a beam from a research project was optimized with regard to material consumption and greenhouse gas emissions. It was investigated whether the beam, which has already an improved environmental impact compared to conventional reinforced concrete due to the materials used, textile reinforcement and ultra-high strength concrete, could be further optimized. For this purpose, the beam was manufactured with different eco-concretes, which were locally graded over the length and the cross-section in order to adapt the performance to the requirement in the best possible way. Optimum utilization of the concrete properties makes it possible to save large quantities of cement.To verify the feasibility of the optimization strategies, cement-reduced concretes were produced and their strengths tested. Furthermore, it was investigated whether and how a local gradation over the length is possible and how the joints between the concrete types behave.On the basis of a comparison of the greenhouse gas emissions in the form of a life cycle assessment, it can be shown that these can be significantly reduced by the selected optimization strategies for the textile concrete. Finally, it was also possible to demonstrate the feasibility in principle of vertical grading by using a vertically movable plate to seperate the concrete layers without the occurence of instabilities.

gradiert; textilbewehrt; Betonbauteile