Ground Penetrating Radar (GPR) is a useful nondestructive testing tool that can locate buried objects or conditions below the ground surface or in a massive medium such as concrete. The data is collected and processed continuously by a portable computer module, generating real-time results.
Applications
GPR can locate both metallic and non-metallic objects in concrete and masonry up to 18” thick, including:
For concrete and masonry applications, special post-processing software can be used with a scan pad to create a depth slice image of a 2' x 2' slab or wall area. The image allows AET to evaluate the location of objects in the concrete relative to depth. This is helpful in determining what type of object (e.g.: conduit, reinforcing steel, etc.) has been detected, or estimating the depth of concrete distress (e.g.: delamination, void, etc.).
Below the ground surface to depths of up to 30 feet, GPR can detect conditions such as:
Safety
The instrument does not emit harmful radiation. Normal business operations may be maintained while our GPR work is performed. There is no need to evacuate the areas being surveyed as required with x-ray or radiographic testing. The total power output of the unit is less than that of a CB radio.
Methodology
The GPR system functions by radiating low-power, radio-frequency electromagnetic pulses from the antenna into the subsurface. The size of the antenna and the electrical properties of the subsurface materials determine the depth of signal penetration and the quality of signal resolution. As the pulse travels through the subsurface, reflections occur at boundaries where there is a dielectric contrast (change of materials or moisture condition). The reflected portion of the signal travels back to the antenna and is processed and displayed by the control unit in real time.
Displays
Once the data has been processed by the control unit, it can be displayed in several forms. The most common displays are linescan grey scale and linescan color scale.
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Figure 1
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Figure 2
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When the 2' x 2' scan pad is used, a depth slice display can be generated by post-processing the data. The two images below show a concrete slab with reinforcing steel bars in two directions.
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