Corrosion of reinforcement bars (re-bar) in structural elements made of 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 reinforcement. However, certain structural elements such as 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 that enables the conditions of reinforced concrete elements covered with asphalt pavements or other layers to be studied is desirable.
Work carried out by Empa and other institutions suggests the suitability of ground-penetrating-radar as a means to inspect 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 being uniform. Some authors found that radar results compare favourably with results obtained by other methods, whereas others came to the conclusion that the results do not fit 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, in particular, for the non-destructive detection of chloride ions in concrete. The project will be carried out within the framework of a PhD-thesis and will involve three partners (Empa, EPFL, Forschungszentrum Jülich) to ensure that all relevant aspects are covered and supported by specialists.
This proposal aims at a unique combination of theoretical aspects, modeling, inversion, laboratory experiments and a field test. This will answer several questions currently discussed by the scientific community and foster the application of innovative and beneficial inspection methods in civil engineering.