Current GPR Does Not Compare To BridgeScan® for bridge inspections.
A newer approach to bridge deck assessments is Ground penetrating radar (GPR). GPR utilizes a high-frequency radio signal that is transmitted into the ground while the reflected signal is captured by a receiver and stored on digital media. A computer system determines the time taken for a pulse to travel to and from the target and shows its location and depth. Reflected signals are interpreted by the equipment and displayed on a screen. The reflected signals are used to detect changes in material, cracks, voids, and objects. The technique is used to assess the uniformity and quality of concrete highway surface and detect the deterioration of bridge decks. GPR for bridge surface measurement can be air-launched or ground-coupled.
Ground-coupled GPR uses an antenna placed close to the surface while air-launched systems use directional antennas that are aimed at the surface of the structure from the height of between 30 and 40 centimeters. Ground-coupled antennas are slow but less prone to less prone to radio frequency interference. Air-launched antennas can be used even when traveling at 120 kilometers per hour. The location of objects such as post-tension cables, conduits, and rebar embedded in the concrete uses a high-frequency GPR system. The data can be gathered in a grid format to produce a map of any targets on the concrete, or a simple line scans to determine the thickness of the concrete. While acoustic is subjective, GPR is more quantitative and is not affected by noise. GPR however provides a lot of data not easily interpreted by asset owners.
Ground penetrating radar has many other applications apart from nondestructive testing of bridge decks and approach roadways. The applications include the study of ice, groundwater, bedrock, and soil. It is also used in the mapping of archaeological features, detection of tunnels and mines by the military and location of underground utilities.