Feasibility studies on monitoring corrosion of rebar embedded in concrete by optical fiber grating

Based on the fact of the volume change of rebar embedded in concrete structure after being corroded, a new type of corrosion sensor used to monitor reinforcing steel embedded in concrete was developed. To validate this corrosion sensor whether or not, the optical fiber grating was pre-strained before it is fixed on the surface of cylindrate steel bar, and put it into 5% of sodium chloride solution for accelerating corrosion. The strain will be released when the steel is eroded, the wavelength of fiber Bragg grating (FBG) will be changed accordingly. The corrosion depth can be measured by detecting the wavelength of fiber grating. Experiment showed that the optical fiber grating can be used to monitor the corrosion of rebar in concrete, and the precision is better than 0.1 μm and the measuring depth scope of 12 μm can be obtained. The sensor can be used to monitor the early corrosion of reinforcing steel in concrete structure.