Ultra-high performance concrete for the repair and strengthening of bridges - Part 1: Application spectrum, material, and construction

An increasing number of road bridges in Germany shows deficits in terms of structural safety and durability. Replacing these structures by new ones is cost-intensive and requires considerable material and human resources. A look at neighbouring countries shows that the repair or strengthening of bridge superstructures by means of thin reinforced cover layers made of ultra-high performance concrete (UHPC) represents a cost-effective and, above all, durable alternative to reconstruction. The first part of this article presents basic options of applying UHPC with existing bridges and explains construction methods. The special suitability of UHPC for this field of application results from the impermeability of its microstructure and its resistance to all forms of chemical and physical attack, so that UHPC can also be used for bridge decks without further protective measures. UHPC differs fundamentally from normal and high strength concrete in its material properties. Therefore, these aspects are examined in detail in a comparative manner. The most important mechanical properties are also presented. The information can be used, for example, as a basis for project-related approvals, for the development of technical guidelines or for the technical content of the construction contract. Aspects of manufacturing and quality assurance measures are discussed in the second part of this article.