Evaluation of Nonuniform Corrosion of Steel in Concrete Based on Two-Yoke Magnetic Sensor

The present study aims to develop a two-yoke magnetic sensor system, measuring the mass loss of steel in concrete subjected to nonuniform corrosion. The impressed current method was employed to induce the nonuniform corrosion of steel in concrete specimens. Experiments and theoretical calculations based on the finite-element method were performed to verify the effectiveness of the two-yoke magnetic sensor. Parametric analyses were carried out to investigate the effects of distribution of rust layer, the geometry of steel bar, as well as the depth of concrete cover on the results of magnetic flux density sensed by the sensor. Results showed a good accuracy in estimating the mass loss of nonuniformly corroding steel by the change of magnetic flux density. Little influence was exhibited by varying the amount of corrosion products including the distribution of rust layer and the volume expansion ratio. It revealed the effectiveness and accuracy of the two-yoke magnetic sensor in quantitatively evaluating the corrosion degree of nonuniformly corroding steel irrespective of different distributions of rust layer. With respect to the sensitivity in structures with large concrete cover, the two-yoke magnetic sensor demonstrated a better performance than the external magnetic sensor.