Voided Post-Tensioning Ducts

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July 9, 2015

The presence of voids in the ducts of post-tensioned structures such as bridge decks is matter of considerable concern because the necessary rehabilitation of voided ducts is a costly process.


For bridge owners and operators there is a requirement for non-destructive inspection techniques to assess the conditions within the ducts without intrusive breakouts involving concrete removal to expose the ducts for visual inspection.


Impact Echo is a system frequently used to identify voids in metal ducts, particularly at shallow depths.

When Ground Penetrating Radar is combined with Impact Echo, the engineer can accurately plot the profile of a metal duct on the surface and determine if voiding is present in the duct without the need for concrete removal and visual inspection. Some duct and tendon exposures are however recommended to confirm the results of the non-destructive testing.

Infrastruct AMS has the full capability in-house to locate ducts with GPR and carry out impact echo testing on post-tensioned structures. For more information please contact Dr Thomas Callanan in Infrastruct AMS.

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