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Acoustic Emission Corrosion Monitoring of Prestressed Concrete Bridge Members

Corrosion of prestressing steel strands in concrete bridge members may lead to the rupture of single strands and catastrophic collapse before visual inspection uncovers evident signs of damage, and well before the end of the design life. Recognizing corrosion in its early stage is critical to plan maintenance and repairs and prevent premature failures. The acoustic emission (AE) technique is a rational means to develop structural health monitoring and prognosis systems for the early detection and location of corrosion in prestressed concrete. It is sensitive to micro- and macro-damage, non-intrusive, and suitable for remote monitoring. However, there is little understanding of the correlation between AE and the extent of early damage in prestressing strands. This paper presents recent advances in AE monitoring of corrosion for prestressing strands embedded in concrete. The state of the art is reviewed, and results from recent research efforts are reported, in which prestressed concrete specimens representative of scaled bridge girders and piles were exposed to salt water through wet/dry cycles. The acoustic emission activity resulting from the early corrosion of strands was studied by evaluating AE data vis-a-vis electrochemical measurements and evidence from scanning electron microscopy.