NON-DESTRUCTIVE LOCATION OF TENDON DUCTS IN CONCRETE BRIDGES FOR THE INSTALLATION OF NOISE INSULATING WALLS USING IMPULSE RADAR

For preventimg damage of tendon ducts in concrete bridges during the installation of noise insulating walls, the crosswise tendon ducts were located using impulse-radar. Due to the incorporation of a metal foil under the asphalt layer in the bridge construction, the measurements were performed from the bottom of the bridge using a crane lorry with a moveable platform. For the data of a few areas with an enhanced density of reinforcement, further data processing was necessary. In order to decrease the intensity of the reflected signals from the reinforcing bars, the polarisation of the electrical field of the antenna was oriented parallel to the direction of moving, i.e. perpendicular to the reinforcing bars. Investigations of test specimens have shown that for distances between the reinforcing bars which are less than 10 cm, only transmission measurements are capable of locating the tendon ducts behind lying. For the covering abstract see ITRD E111699.