Application of Confocal Micro-X-ray Fluorescence Technique for Non-destructive Elemental Inspection of Damaged Reinforced Concrete

Abstract

In this study, we obtained elemental distributions around the scratch in reinforced concrete. Confocal micro-X-ray fluorescence (CM-XRF) technique was employed for observing a sample cross section without destroying the sample. We prepared a rebar fragment, and then it was covered with concrete. The test sample was scratched with the band saw with a blade of ~1 mm width. The scratched test sample was measured using a laboratory-made CM-XRF instrument. As for the Ca distribution, the thickness of the concrete layer was estimated to be ca. 100 μm. In addition, the depth and width of a scratch were calculated to be ca. 150 μm and 1.1 mm, respectively, as observed from the Fe distribution. And then, we observed the corrosion products resulted by immersing the reinforced concrete in NaCl solution. Sphere-shaped structures were seen in the Fe and Cl distributions, therefore, we considered that it to be the corrosion product containing iron chloride. It is expected that by using a sample cell for in-situ observation, it will be possible to observe the corrosion process of reinforced concrete in real time.