Air permeability assessment in a reinforced concrete viaduct

When the deterioration key factor is steel corrosion, the lifetime of reinforced concrete structures highly depends on the permeability and thickness of concrete covering reinforcing bars. Adequate permeability is usually achieved by means of assuring a minimum cement content, maximum water to cement ratio and minimum compressive strength. The new European Standard for concrete (EN 206-1) allows performance design methods with respect to durability, for instance by the specification of values for some relevant concrete properties. However, these properties are to be determined on standard specimens and therefore only allow distinguishing the potential performance of different concrete compositions. As there are other factors, such as placing, compacting and curing, which influence concrete permeability results, it is extremely important to evaluate the real permeability of concrete in structures. This work presents an assessment of a viaduct’s concrete air permeability using the Torrent Permeability Tester (TPT). The tests were performed in different structural elements made of concrete of two different strength classes. The obtained results from structural elements were compared with those obtained from cast specimens, cured, preconditioned and tested under laboratory conditions. This comparison shows significant differences between both situations, pointing out that a reliable durability approach should also include specifications for site durability related properties and rules for its conformity control.