The impact-echo technique has been used for over twenty years to evaluate hidden defects in various concrete structures. Post-tensioned bridges present unique challenges for testing with available nondestructive techniques including the impact-echo method mainly because of their design characteristic. The design includes thicker concrete members with congested reinforcing steel and stacked post tensioning ducts and therefore embedded defects are difficult and sometimes impossible to detect with the available techniques. This paper describes some of the applications to detect cold joints and delaminations in bridge decks, the condition of the grout in post-tensioning ducts and testing of repair quality of pressure injected cracks.
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