Experimental study and simulation of reinforcement distance from concrete surface using eddy current

Non-destructive test is one of the techniques that is used to ensure the health of concrete structures. In order to retrofit concrete columns, it is necessary to know the number of reinforcement steel bars embedded in concrete and their cover to the concrete surface. In this paper, for the purpose of obtaining the reinforcement cover to surface of concrete in concrete columns, finite element simulation is performed by using Maxwell software and a special type of measuring probe is designed and fabricated. When a conductor such as reinforcement steel bar approaches the coil and ferrite core, the reinforcement bars interacts with low frequency electromagnetic waves, and by measuring of these waves’ effects from the concrete surface, the location of the reinforcement can be estimated. The designed probe was tested on different reinforcement covers with various frequencies and the recorded results were evaluated. The reinforcement cover can be estimated from the inductance variation and the ohmic resistance of the coil while the frequency and voltage are kept constant. Effects of the reinforcement cover to the concrete surface and frequency on the ohmic resistance and inductance of the probe are evaluated by using three-level full factorial designs and a regression model from effective parameters is prepared. Finally, the neural network is employed to estimate the reinforcement cover with different values of frequency, the reinforcement cover to concrete surface and the ohmic resistance of probe.