Ultra-high performance concrete for the repair and strengthening of bridges - Part 2: Producing UHPC, application on-site, and quality assurance

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, which are hardly available to the necessary extent given the size of the task to be accomplished. 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 durable alternative to reconstruction. 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. In this aspect as well as regarding its mechanical properties, UHPC differs fundamentally from normal and high strength concrete. In the first part of this article, the various possibilities of applying UHPC with existing bridges are presented and the special material properties are explained. The present second part of the article deals with the production of UHPFRC, the application on-site and quality assurance measures. As with part 1, the information can be used, for example, as a basis for project-related approvals, for developing or supplementing technical guidelines and for drafting the construction contract.