Abstract
Most of the structures in the transport infrastructure are built of reinforced concrete, and many of our large bridges are built of prestressed concrete. A large part of these were built before 1980, and could theoretically have problems with both corrosion in tension cables, chlorides in injection mills and thin lightly damaged feed pipes. After 1980, the standards were tightened. Whether these theoretical problems are real is not fully mapped as basic investigations of these bridges have not been conducted in Sweden. International attempts have been made with methods of non-destructive testing (NDT) to identify problems in the form of cavities, corrosion or breakage in cables. These investigations have had limited success since no individual measurement technique has been shown to be able to be used to map the condition. However, it has also been shown that a combination of different NDT techniques can overcome some of the challenges and detect defects in ducts in prestressing systems installed in large concrete structures. The methodology described in this paper shows that it is possible to detect damages, but also that the results is very much dependent on the skills of the persons that use the equipment and evaluate the data.