Flaking and delamination of concrete caused by material deterioration or improper casting are normally inspected by hammering. This method, however, poses a number of problems: it relies on the inspector's sense of hearing and experience, there are too many structures to be inspected, and inspectors are required to work in high places. The RTRI has therefore developed a simple and accurate system for the diagnosis of concrete (Fig. 1).
      There are a number of issues to be addressed in a commercially available shooting system combining infrared and visible-ray cameras, including complicated image processing and low image precision. The RTRI has therefore promoted the development of a new system aimed at the real-time output of high-precision processed images, the quantification of degraded parts, and a diagnosis system directly applicable to field work. The newly developed system has the following features:

1)	High-sensitivity infrared cameras allow judgment of the degradation of structure cover concrete in open sections without the use of heaters or xenon lamps, irrespective of ambient daytime temperature changes (Fig. 2).
2)	The functions for measuring angles and distances using laser beams incorporated into the cameras enable calculation of the length, area and position of degraded parts from a distance.
3)	Processing blended infrared and visible-ray images at high precision enables analysis of degradation in the field on a real-time basis.

      When heating is applied, the system can detect flaws at points deeper than the thickness of normal cover concrete.
      This system enables efficient diagnosis of concrete for flaking and delamination, and is expected to improve the safety of concrete structures against those who are not directly related to the railway operation.

Fig. 1 Appearance of the concrete diagnosis system's components

Fig. 2 An example of blended infrared and visible-ray images.

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