Development and performance research of FBG strain sensor for monitoring on asphalt concrete pavement

Stiffness of asphalt concrete is very low, so ordinary FRP or steel packaged sensors are not suitable for measuring its strain accurately. In view of the problem, one innovative kind of optical fiber Bragg grating sensor packaged with polypropylene, a thermoplastic resin, was proposed in this article. Firstly, a conveniently assembled and dissembled steel die was designed and fabricated. Then, after characteristics study of polypropylene during heating and cooling repeatedly, the reliable grouting technique was formed. After this, real-time monitor of the entire sensor packaging process including die apartness was performed, and then, the sensor mechanics performance, the microscopic structure and other properties were studied thoroughly. Results of SEM indicate that interface of optical fiber and polypropylene is considerable tight. Measured strain during sensor making is reasonable. The FBG sensor was also embedded into a concrete column to measure its strain during continuously 7 day-long early-age solidification and compressive strain. Additionally, the FBG was also used to measure strain of asphalt concrete beam. Linearity and repeatability of the sensors are quit well and measured strains are quite believable. So, we can say that due to deformation compatibility between packaged material and FBG, FBG sensor and be measured material, especially low modulus of packaging materials, the strain of asphalt pavement can be monitored reliably by the sensor.