Road Pavement Structural Health Monitoring by Embedded Fiber-Bragg-Grating-Based Optical Sensors.

Fiber Bragg grating (FBG) optical sensors are state-of-the-art technology that can be integrated into the road structure, providing real-time traffic-induced strain readings and ensuring the monitoring of the road's structural health. By implementing specific FBG sensors, it is possible to detect each vehicle's axle count and the induced strain changes in the road structure. In this study, FBG sensors are embedded at the top of the 240-mm-thick cement-treated reclaimed asphalt pavement mixture layer of the road (specifically, 25 mm deep within the road). Optical sensors' signal interrogation units are used to measure the strain and temperature and collect data of the road's passing vehicles, starting from passenger cars that have two axles and up to heavy trucks that have six axles. Passenger cars with 2 axles generate a typical (90% events) strain of 0.8-4.1 μm/m, the 2-axle minibus 5.5-8.5 μm/m, 2-3-axle trucks 11-26 μm/m, but 4-6-axle trucks 14-36 μm/m per each axle. A large number of influencing parameters determine the pavement design leading to the great uncertainty in the prediction of the strain at the boundary between the asphalt surface and cement-treated base layers. Real-time strain and temperature measurements help to understand the actual behavior of the pavement structure under an applied load, thus assisting in validating the proposed pavement design.