Faserorientierung im selbstverdichtenden Beton mit der Produktionsoptimierung für den Tübbingbau mit Schnellzement (English shop)

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For purely fibre-reinforced components, it is repeatedly claimed that there is no fibre orientation and that fibre-reinforced concrete is an isotropic building material. In concretes with low viscosity and thus high flowability, as is the case with self-compacting concrete, a fibre orientation has often been suspected and in some cases also observed.

In this work, the fibre orientation in self-compacting concrete was investigated. For this purpose, a transparent model fluid was first developed which possessed rheological properties comparable to those of the concrete used later. With this fluid it was possible to document the fibre movement during the filling process and during flow, as well as to investigate the fibre movement in a laminar flow. The findings obtained here were validated by tests with self-compacting concrete based on rapid-hardening cement. Owing to its application, the self-compacting concrete was previously subjected to investigations that went beyond the scope of a conventional initial type testing.

In these concrete tests, in addition to different filling methods, the influence of the steel fibre dimensions on the fibre orientation and on the component strength was also investigated. At the end of this section, the fibre dimensions and fibre content for the further tests were defined.

In the segment (tunnel lining) tests, components were produced whose dimensions corresponded to approximately one third of those segments installed in the Unterinntal line. Two different filling methods were applied in the production of these precast elements. The specimens were subsequently examined for their load-bearing and post-cracking behaviour in the installed condition using an adapted 4-point bending tensile test method.

Finally, two segments were produced in the field factory for the Kaunertal power plant. This test showed that production with self-compacting concrete based on rapid-hardening cement is readily possible. The investigation of the fibre orientation in these segments confirmed the results established in the preceding laboratory tests.

From the investigations carried out, rules could be developed for the production of tunnel lining segments with fibre-containing self-compacting concrete in order to achieve a fibre orientation that is optimal for the component.