Effects of bonding on Fiber Bragg Grating (FBG) sensor for monitoring steel corrosion condition in concretes

Steel corrosion in concrete is harmful but invisible. Until now, it is still very hard to measure the steel corrosion condition by non-destructive method accurately. In this paper, Fiber Bragg Grating (FBG) sensors include single and three grating sensors, are proposed to bond with steel bar and embed in concrete for monitoring the steel corrosion condition. The steel corrosion condition is evaluated by the corrosion ratio and volume expansion coefficients of steel, which are derived from the wavelength shift of FBG. Bonding materials and bonding ways are investigated in detail for improving the accuracy of FBG sensors. The mechanism of bonding effects on FBG sensor for optimizing the accuracy, has been discussed. The results suggested that the steel corrosion condition is successfully monitored by calculating the corrosion ratio of 2.02–4.24%, and volume expansion coefficient of 2.18–2.65 in this test. The research work is more quantify than the traditional methods for monitoring the steel corrosion condition in concretes. It is helpful for ensuring the safety operation of infrastructures efficiently.