Historical structures in exposed concrete – Gentle repair and preservation

The repair of historical concrete structures must aim for the preservation of the original construction and the appearance of the concrete surface. This requires adequate methods that minimize the intervention on the building fabric while guaranteeing durability and structural safety. Particularly for the repair of exposed concrete, also termed architectural concrete, local repair rather than treatment of the entire concrete surface should be carried out whenever feasible on the basis of technological considerations. Such an approach requires a detailed investigation of the structure as well as an estimation of the remaining lifetime of still undamaged sections of the structure by modern probabilistic and numerical tools. Suitable repair concretes have to be developed that, in addition to visual similarity with the original concrete, must satisfy certain requirements with regard to their mechanical and physical properties. In this paper, the basis of the methods and procedures for adequate repair work on historical buildings and structures is presented. Finally, the gained experience from the application of the presented method of gentle concrete repair is summarized.