Corrosion monitoring of concrete structures by optical fiber grating sensing

The feasibility of an optical fiber grating corrosion sensor with two steel bars is studied in the present paper. It is demonstrated that while Bragg gratings is tensioned, the reflected spectrum will have a single distinct peak shift in center wavelength. Strain measurement with Fiber optic grating ( FBG) sensors is investigated to monitor strain in reinforcement steel corrosion. FBGs are used to monitor corrosion in aging reinforcement steel, for which the principle is that the steel volume will be expanded due to corrosion, as well as the diameter. Based upon fabrication techniques and sensing mechanism, the monitoring will be carried out by transforming the diameter increase to the fiber strain, as a result the loss and rate of steel corrosion can be obtained. In addition, the strain induced by temperature fluctuation is also measured by an extra fiber grating sensor. Therefore by two independent FBG sensors, the volume changed by corrosion can be separated. By the designed sensor, corrosion is recorded with the shift in center wavelength through the fiber, and the degree of corrosion of reinforcement steel will be measured directly, which is not affected by corrosion factors. Therefore the sensor proposed in the paper could be used in the early corrosion monitoring of reinforcement steel in concrete structures.