Boundary Element Simulation for Identification of Steel Corrosion in Concrete Using Magnetic Field Measurement

A method to identify corrosion of steel in concrete is introduced by combining magnetic field measurement and a boundary element inverse analysis. A better sensitivity of corrosion identification can be achieved if the superconducting quantum interference device (SQUID) sensor could be applied to measure a very low magnetic field on the concrete structure as a result of the impressed current and corrosion of the reinforcing steel. In this method, the inverse problem is formulated by minimizing the cost function, which is a residual between the measured and calculated values of magnetic flux densities on the concrete surface. The magnetic flux density is calculated based on the law of Biot and Savart and takes into account the current that flows in the concrete domain and in the reinforcing steels. Laplace’s equation is solved by the boundary element method to obtain the potential and current density in the concrete domain and in the whole surface of the domain. Although the ferromagnetic effect is neglected in this simulation, it is suggested from the numerical simulations result that the method can be used to accurately detect an early corrosion of the steel in concrete and the corrosion of the second-layer steel in the concrete structures.