Electromagnetic tomography for the rebar inspection in concrete

Abstract Electromagnetic Tomography (EMT) is a non-destructive testing technique that reconstructs images of conductivity distributions within a sensitive field based on boundary electromagnetic measurement data. This technology offers the advantages of a simple structure, low cost, non-contact operation, non-invasiveness, and rapid imaging, making it widely applicable in industrial and medical fields. Currently, methods for detecting the diameter of rebar in concrete suffer from high costs, operational complexity, and poor imaging quality, with a lack of low-cost and effective detection solutions. EMT technology can effectively address these challenges. In this work, an EMT system with a 9-coil planar array sensor is employed to detect rebars of varying diameters, and its effectiveness is validated through finite element simulation software. Furthermore, an EMT image reconstruction algorithm is proposed, which utilizes a primal-dual acceleration algorithm to solve a multi-objective feature function incorporating <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">L</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> </mml:msub> <mml:mo>−</mml:mo> <mml:mi mathvariant="normal">norm</mml:mi> </mml:math> and Total Variation (TV) regularization. The numerical simulation results demonstrate that, compared to traditional algorithms, the proposed method achieves reconstructed images closer to the true distribution with minimal error, enabling more accurate reconstruction of detection targets. Moreover, it exhibits superior robustness, and real experiments validate its high efficacy in practical detection. This highlights its potential for practical applications in concrete reinforcement inspection.