Comparisons between two corrosion assessment methods and the corrosion of steel in prestressed concrete

In 2002, the 45 year old Sorell Causeway Bridge in Tasmania’s south east was demolished due to fears surrounding the serviceability of the prestressed concrete beams, in relation to the corrosion of the post-tensioning strands. Attempts were made to determine the extent and severity of the corrosion prior to its demolition by employing a number of conventional non-destructive and diagnostic techniques, yet a firm conclusion could not be reached regarding the structure’s condition. To further investigate the degree of correlation between these conventional assessment techniques and the physical condition of the embedded steel in relation to corrosion risk guidelines recommended in the literature, a number of beams of varying condition were salvaged from the bridge demolition and subjected to further detailed investigations. The current paper focuses on the half-cell potential and chloride profile results obtained for two such beams in good and poor condition relating to the reinforcing and prestressing steel condition. In summary, the comparison of results yielded inconsistencies with the literature guidelines. Survey areas showing highly negative potentials and elevated chloride concentrations did not necessarily indicate corrosion activity or severity. In contrast, instances of severe corrosion were found on both reinforcing and prestressing steel where literature guidelines for these tests recommend that the risk of corrosion is low.