Delamination detection on a concrete bridge deck using impact echo scanning

Abstract

In this large-scale field study we use a prototype impact-echo scanner to detect delaminations on a concrete bridge deck surveying in total over 17,000 m2. Delaminated bridge sections are known from manual sounding and coring. A large-scale damage assessment is necessary to identify the need of repair work. Based on first results, two lanes of the bridge are repaired and in subsequent tests the bonding of fresh and old concrete is examined. It shows that delaminations found on the bridge deck surface are unevenly distributed with more defects on the southbound lanes. This indicates constructional problems during the concrete placement. The developed scanner excites stress waves by dropping steel solenoids on the surface and recording the impact-echo frequency by air-coupled microphone arrays. It is pushed at a speed of 600 m/h, hitting the surface 300 times per square meter. The recorded data is preprocessed on site with an automated delamination detection threshold implemented. Found delaminations are transferred to a bridge map to allow an overall damage assessment.