Experimental and numerical study of an electromagnetic sensor for non-destructive evaluation of steel corrosion in concrete

Abstract

Corrosion of steel is one of the major causes for the degradation of reinforced concrete (RC) structures. In this regard, the assessment of reinforcement corrosion is critical in evaluating the service life of RC structures. The present study aimed to develop an electromagnetic-based apparatus which can be externally positioned on RC structures, to detect and monitor the corrosion of embedded steels. Experiments and numerical simulations based on finite element method (FEM) were carried out to verify the effectiveness of the external electromagnetic (EM) sensor. Different degrees of corrosion for steel in concrete specimens were obtained by impressing current method. Experimental results showed a linear relationship between the mass loss of corroding steel and the change of magnetic flux density sensed by the external EM sensor. Compared with the numerical results obtained from FEM simulations, a good accuracy was exhibited in estimating the mass loss of corroding steel in concrete by the change of magnetic flux density. Numerical simulations were further conducted to investigate the effects of the dimension and position of steel, the distance between testing surfaces of the EM sensor, and the magnitude of magnetic field intensity. As a non-destructive technique, a promising application of the external EM sensor was demonstrated in terms of evaluating the corrosion degree of steel in concrete, with the feasibility to increase its sensitivity by controlling the driving current and coil turns.