In this paper, the relationship between production parameters of ultra high performance fiber‐reinforced concrete (UHPFRC) and the spatial distribution and orientation of the steel fibers is investigated. UHPFRC specimens with varying fiber diameter, fiber volume fraction, and rheology of the mixture are produced. Additionally, casting is performed from the side or the middle of the formwork. Imaging by micro computed tomography allows for a statistical analysis of the spatial arrangement of the fibers in the test specimens. The flexural behavior and the load capacity of the specimens are analyzed by four point bending tests. The results of the bending tests are well explained by characteristics of the fiber systems determined from the image data.
The influence of the specimen size of ultra‐high‐performance fibre‐reinforced concrete samples on the spatial distribution and orientation of the steel fibres is investigated. Specimens of varying size are produced by using the same protocol. They are imaged by micro‐computed tomography to perform a statistical analysis of the spatial arrangement of the fibres. The tensile strength of the specimens is measured by tensile tests on subspecimens of equal size. The results are correlated to geometric characteristics of the fibre systems determined from the image data. Increasing the specimen size results in a larger variability of the local fibre geometry. This effect was most prominent when increasing the height of the specimens.
In this paper, a prediction model for the tensile behaviour of ultra-high performance fibre-reinforced concrete is proposed. It is based on integrating force contributions of all fibres crossing the crack plane. Piecewise linear models for the force contributions depending on fibre orientation and embedded length are fitted to force–slip curves obtained in single-fibre pull-out tests. Fibre characteristics in the crack are analysed in a micro-computed tomography image of a concrete sample. For more general predictions, a stochastic fibre model with a one-parametric orientation distribution is introduced. Simple estimators for the orientation parameter are presented, which only require fibre orientations in the crack plane. Our prediction method is calibrated to fit experimental tensile curves.
Hochleistungsbetone eröffnen völlig neue Anwendungsgebiete für mineralische Baustoffe. Bei dem Versuch, bisher etablierte Bauweisen zu substituieren, spielt neben der Erreichbarkeit wirtschaftlicher und ökologischer Vorteile auch die Freude am Ausprobieren und am Antizipieren zukünftiger Entwicklungen eine wichtige Rolle.
Der mit diesem Beitrag geehrte Jubilar hat in diesem Zusammenhang unzählige eindrucksvolle Beiträge geliefert, die übrigens weit über den Einsatz neuer Werkstoffe und Materialien hinausgehen, und inspiriert zu immer neuen Anläufen.
Im vorliegenden Aufsatz soll am einfachen Beispiel von selbsttätigen Hochwassersperren gezeigt werden, wie ein werkstoffgerechter Einsatz von Baustoffen neue sinnvolle Lösungen ermöglichen kann. Jederzeitige Verfügbarkeit, geringe Herstellkosten, hohe Dauerhaftigkeit und geringer Wartungsaufwand sind dabei angestrebte Zielgrößen.
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