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Corrosion mapping with the GPR method

Corrosion caused by chlorides is one of the main causes of damages to reinforced concrete structures and is responsible for most of the repair costs.

The GPR (Ground Penetrating Radar) method can quickly map at reasonable cost, areas of corrosion on large surfaces, such as bridges, overpasses and parking lots.

GPR method is an electromagnetic measurement method.
It is most often used in reflection mode in which a signal is transmitted by an antenna in the structure to be assessed. The energy reflected by changes in material properties is recorded.

The amplitude of the reflection at the interface between two materials depends on many factors such as the difference in material properties, particularly the difference in their dielectric constants, the amplitude of the transmitted signal or the radar signal attenuation in the material above the interface.

Radar signal attenuation and depth of penetration, closely dependent on the electrical conductivity of the scanned concrete. When concrete has high electrical conductivities, the radar signal is converted to leakage currents, which increases the signal attenuation and reduces the attainable depth of investigation.

Moisture and chlorides content of the concrete have a direct influence on the signal attenuation and amplitudes of reflections transmitted to the GPR antenna.

Mapping of corrosion levels areas, with the GPR method, is based on this principle, and areas of different corrosion potential are mapped according to the amplitude of the reflected radar signal on rebar and / or on the asphalt /concrete interface.

Example of a bridge deck corrosion map
 Cartographie des zones de corrosion d’un tablier de pont

The GPR (Ground Penetrating Radar) method can quickly map at reasonable cost, areas of corrosion on large surfaces, such as bridges, overpasses and parking lots.

Mapping of corrosion levels areas, with the GPR method, is based on this principle, and areas of different corrosion potential are mapped according to the amplitude of the reflected radar signal on rebar and / or on the asphalt /concrete interface.