The multi-floor underground carpark "Altes Haus" located in the city of Mannheim, is a highly frequented short-term parking complex for an adjoining hotel and retail complex. The carpark was constructed in 1964 with the ‘Anselment System” containing a minimum number of columns with large internal spans to improve car parking operations.
It was detected that chloride-induced corrosion had occurred over a number of years from water containing high concentration of de-icing salt dripping from the vehicles. The chloride corrosion had resulted in pitting as well as a reduction to the effective cross-sectional area of the reinforcing steel.
Due to structural considerations the removal of full scale contaminated concrete in the structure was not economically feasible. Instead selected reinforcement replacement was performed in conjunction with the application of a cathode protection system in conformance to principle ‘K’ of the building specification.
This cathode protection system effectively prevents any further damage to the reinforcing steel, despite high levels of chloride remaining within the structure.
Due to the anticipated high currents required in the system to protect against the excessive chloride values a series of titanium ribbon anodes were horizontally embedded within the slabs. Additionally to the base of selected columns and walls a further series of titanium ribbon anodes were applied.
Awarding authority: HAGEMA Verwaltungsgesellschaft für Haus und Grundbesitz GmbH N6.3, Mannheim
Client: BWS Rhein-Neckar, Heidelberg
Design: Ingenieur-Büro für Tragwerksplanung Dipl.Ing. Hanisch + Heck, Köln