Development of electromagnetic sensors for corrosion assessment of reinforced concrete structures

Abstract

This paper describes the development and tests of ECT sensors, dedicated to identifying the existence of corrosion processes in reinforced concrete structures. The electromagnetic part of the sensor is an RLC series circuit, fed by a high-frequency electronic source. The inductive reactance of the sensor (L) is provided by a multi-turn coil, the capacitance (C) is an external arrangement of capacitors, and the resistance (R) is the sum of the coil resistance itself plus an external resistance. Three different prototypes were built. The presence of ferromagnetic bodies under the sensor disturbs the electromagnetic and consequently the inductive reactance. As the sensor is designed to operate near the resonance frequency, substantial change will occur in the measured voltage on the capacitor. This change of voltage is used to identify the presence, position, bar gauge and even corrosion processes in the elements of the armature of reinforced concrete structures. The paper presents the mathematical principles, electronic and electromagnetic developments, tests and analysis of the results.