Ultra-high-performance concrete – UHPC is a type of concrete characterized by a very dense microstructure entailing a high compressive strength (>150 MPa) and an outstanding durability. In addition, UHPC exhibits a high resistance against chemical and mechanical exposure. Due to the very brittle failure mode, fibres are usually added to the fresh concrete in order to enhance the ductility of the hardened concrete. In dependency of the fibre content and type, crack bridging can be achieved, resulting in a tensile strength which exceeds the tensile strength of the cementitious matrix.

Guideline for the usage of UHPC in Austria

Significant progress has been made by researchers in recent years in terms of UHPC, making them attractive for practical use. Nonetheless, these innovative materials have not been able to get beyond a couple of pilot applications. A main reason for the start-up difficulties are the missing regulations for the application of UHPC in Austria. While other countries such as Switzerland, France or Japan have issued guidelines and standards promoting the usage of UHPC, Austria has been rather reluctant in the past. In order to create a legal framework now for the Austrian construction industry a consortium consisting of Austrian universities and representatives of the building industry formed in 2019. Accompanying the preparation of the guideline, a research project is being carried out targeting open research questions which are of importance for the development of the guideline.

experimental setup and monitoring

Fatigue tests at TU Wien

In the course of the aforementioned research project the Institute of Structural Engineering at TU Wien will be investigating the fatigue behaviour of UHPC. For this purpose, fatigue tests are planned to be carried out in the laboratory of the Institute. The fatigue strength of the UHPC under consideration of the concrete being initially loaded above the matrix tensile strength (strain hardening has already occurred) is of particular interest. This situation can arise, for example, when a bridge deck slab is strengthened with a top layer of UHPC. The tensile strength is exceeded due to impeded shrinkage, which causes the matrix tensile strength to be exceeded. Subsequently fatigue loads are induced by traffic. The aim of the investigations is to provide design criteria for UHPC under cyclic loadings, which can then be incorporated into the new guideline.

Financing of the research project

he research is conducted as collective research, with the ÖBV acting as applicant. The project is financially supported by the FFG and several representatives of the Austrian construction industry.