Recent failures of external prestressing grouted tendons: when the ducts take on water…

The article describes recent cases of tendon ruptures by corrosion and investigations carried out on some bridges in France. Several causes related to HDPE ducts have been identified such as damages during handling, threading and tensioning of strands, defective connection of the duct to the anchorage, damage during construction or operation, low quality of HDPE material, etc. These cases of tendon rupture exclusively concern ducts injected with cement grout. To our knowledge, no structure built after the application of the 2001 circular [1] (prohibiting cement grout for the injection of external prestressing) is currently exhibiting major disorders.

A warning note on existing structures with external prestressing has been updated by Cerema in November 2018 [2]. It describes the diagnosis methodology based on analysis of documentation, thorough visual inspection, destructive and nondestructive investigations. New non‐destructive techniques such as guided‐wave ultrasonic technique and magnetic leakage field test using permanent magnets and induction coils are presented. Innovative methods of local repair of the ducts are also described. Finally, different protective devices are analysed in terms of worker safety in the event of a sudden failure of tendon.