Assessment of stress corrosion cracking in prestressing strands using AE technique
Résumé
Detecting corrosion of prestressing strands in concrete structures requires non-destructive techniques like acoustic emission (AE), which allows the monitoring of active defects of the structures. The aim of this work is to adapt AE to structural characteristics of bridges, to detect and localise stress corrosion cracking (hydrogen embrittlement) of tendons. Accelerated corrosion tests with ammonium thiocyanate on tensioned cables have permitted to validate AE system capacity to detect signals coming from hydrogen embrittlement mechanism. Distinction by AE of the different stages of the mechanism (crack initiation, crack propagation, etc.) occurring on prestressing strands is observed. Limited accessibility to strands on bridges has also been taken into account by placing AE sensors on wire anchorage. Results show effects of wave dispersion but the discrimination of AE hits is possible. This work presents the potential of AE monitoring to detect, in their earliest stage, damages to prestressing strands, but the limitation of AE technique is also pointed out.