Corrosion of re-bar within reinforced concrete is a major problem in countries where salt is applied to roads for de-icing and in marine environments. Concrete structures are periodically inspected in order to monitor possible damage caused by chloride induced corrosion of the rein-forcement. However, bridge decks covered with asphalt pavements are not accessible for visual inspection and probing is limited. As a result, the planning of rehabilitation of bridge decks is usually based on a small number of probes. Consequently, the condition of bridge decks can only be assessed with low certainty. Therefore, a method enabling to study the conditions of concrete bridge decks covered by asphalt pavements is desirable.
Work carried out by Empa and other institutions suggests the applicability of Ground-Penetrating-Radar to the inspection of chloride contamination of bridge decks. Different approaches have been suggested and several studies have been carried out on real bridges. However, results are far from uniform. Some authors found that radar results compare favourably with results obtained by other methods while others came to the conclusion that results do not compare very well.
This project aims at a profound investigation of the influence of various parameters on the propagation of electromagnetic waves in concrete and their exploitation for the non-destructive detection of chlorides in concrete. The project will be carried out within the framework of a PhD-thesis and will involve three partners (Empa, EPFL, ETHZ) to ensure that all relevant aspects are covered and supported by specialists.
This proposal aims at a unique combination of theoretical aspects, modeling, laboratory experiments and a field test. This will not only answer several questions currently discussed by the radar community but will also have a beneficial effect on the application of innovative inspection methods in civil engineering.