Iron-oxide-identifying imaging method based on a wide-energy neutron beam for corrosion inspection in reinforced concrete structures

To prevent potential hazards caused by steel corrosion, there is an increase in demand for non-destructive inspection or monitoring of reinforcing steel corrosion in concrete structures. In this study, an iron-oxide-identifying imaging method is proposed that is based on a neutron resonance transmission imaging technique. According to the correlation analysis of the resonance characteristics of iron and oxygen and the elemental fractions, the iron oxides in the corroded reinforced concrete samples were accurately identified and mapped. The volume identification limit of the rust layer was further analyzed, and it is close to 0.1 mm. For the resonance energies of nuclides Fe-56 and O-16 in the tens and hundreds of keV range, the intensity of neutrons at the corresponding energy is only lower about three orders of magnitude after passing through a 40-cm-thick concrete block. The iron-oxide-identifying imaging method could also obtain a clear image of the iron-oxide distribution inside the 20-cm-thick corroded reinforced concrete sample.