Internal Inspection of Concrete Structures using Laser Compton Backscattered Gamma Rays
By H. Kanada, H. Toyokawa and T. Uomoto
Concrete Journal, Vol.45, No.6, Jun. 2007
- Synopsis
- There is a strong demand for non-destructive inspection of reinforcement in concrete structures. It is an emerging issue in Japan because many buildings were built using false earthquake-resistance data. Detection of bar arrangement after completion of construction is attempted in order to verify whether amount of reinforcement was reduced the compared to the design criteria. Non-destructive inspection methods are often used to detect bar arrangement for core boring in order to avoid reinforcement. Radar or electromagnetic methods are often used, and X-ray radiography may be applied if necessary. Radar and electromagnetic methods can also be applied, but only if the cover depth is small. Detection is very difficult when the bar arrangement is complex. X-ray CT scanner using bremsstrahlung X-ray are commonly used for non-destructive inspection of industrial products such as automobile or aircraft components. However, if the X-ray absorption coefficient of a sample object is large, metal artifact presents due to spectrum hardening effect. High permeability quasi-monochromatic photon beam allows acquisition of accurate information about the density distribution of the sample objects. The quasi-monochromatic photon beam is produced by the laser-Compton backscattering from relativistic electrons. National Institute of Advanced Industrial Science and Technology (AIST) have developed a high-energy and quasi-monochromatic photon transmission radiography and CT systems. The authors used the radiography system to inspect reinforced concrete structures with deformed bars of different diameters and cracks with precisely controlled width. The applicability of the method was examined, and the quality of the information obtained from the experiment was discussed.
- Keywords:
- non-destructive inspection, laser Compton backscattered gamma rays, radiography, computed tomography image
