Highway PC Bridge Inspection by 3.95 MeV X-Ray/Neutron Source

Abstract

We have developed portable 950 keV/3.95 MeV X-ray/neutron sources and applied them to inspection of PC concrete thicker than 200 mm within reasonable measuring time of seconds - minutes. T-girder-, Box- and slab- bridges are considered. Now we are to start X-ray transmission inspection for highway PC bridge (box) by using 3.95 MeV X-ray sources in Japan in 2020. By obtaining X-ray transmission images of no-grout-filling in PC sheath and thinning of PC wires, we plan to carry out numerical structural analysis to evaluate the degradation of strength. Finally, we are going to propose a technical guideline of nondestructive evaluation (NDE) of PC bridges by taking account of both X-ray inspection and structural analysis. Further, we are trying to detect rainwater detection in PC sheath, and asphalt and floor slab by the 3.95 MeV neutron source. This is expected to be an early degradation inspection. We have done preliminary experiments on X-ray transmission imaging of PC wires and on-grout-filling in the same height PCs in 450–750 mm thick concretes. Moreover, neutron back scattering detection of water in PC sheath is also explained.

Quantitative Evaluation of Unfilled Grout in Tendons of Prestressed Concrete Girder Bridges by Portable 950 keV/3.95 MeV X-ray Sources

“…Magnetic testing can detect the disconnection of iron rods or wires up to 300 mm in thickness. With a 400 kV X-ray tube, transmitted images of the PC sheath, wires, rods, and grout can be obtained up to 400 mm in thickness, but it takes approximately 1 h. Compared with the above existing methods, we explain and emphasize the advantage of our method using 950 keV/3.95 MeV X-ray sources [14][15][16]. With them, clear detection and visualization with 1 mm resolution of PC iron structures and grout filling at a depth of 400-1000 mm are possible within minutes.…”

“…Compared with the above existing methods, we explain and emphasize the ad vantage of our method using 950 keV/3.95 MeV X-ray sources [14][15][16]. With them, clea detection and visualization with 1 mm resolution of PC iron structures and grout filling at a depth of 400-1000 mm are possible within minutes.…”

“…We used an X-band (9.3 GHz) LINAC-based 950 keV/3.95 MeV X-ray source to inspect the actual bridge [14][15][16]. These systems are shown in Figure 9a,b, respectively.…”

“…Thinning and disconnection were observed with a spatial resolution of 1 mm. Measured flaws such as unfilled grout and thinning/disconnection are input to the structural analysis described in References [16,17]. Thus, the initial poor construction of unfilled grout and serious thinning and disconnection of PC wires are diagnosed, and their effect on the lack and degradation of strength is quantitatively evaluated by structural analysis.…”

“…Figure16. Gray value profile and the polynomial fitting along the line segment in Figure14as the background X-ray intensity distribution.Schematic gray value profiles of the filled and unfilled grout cases are shown in Figure17a.…”