High-accuracy rebar position detection using deep learning–based frequency-difference electrical resistance tomography

Rebar corrosion is one of the most critical mechanisms causing structural deterioration in reinforced concrete structures. However, rebar corrosion assessment is difficult in that typical non-destructive testing methods have limitations in accurately detecting rebar positioning in concrete. This study presents high-accuracy rebar position detection using a deep learning–based electrical resistance tomography (ERT) technique. Two data sets were prepared as input data: (1) the original circular ERT images in a Cartesian coordinate system and (2) the transformed rectangular ERT images in a polar coordinate system. The proposed convolutional neural network (CNN) model successfully distinguished rebar position from ERT images. Most of the radial and angular positions of the rebar were accurately identified by the model, despite rebar’s wide distribution of high conductivity in the raw ERT images. Notably, the detection performance clearly depended on the coordinate types in the ERT images, whether they were Cartesian or polar coordinates.