Experimental Evaluation of FBG Sensors for Real-Time Strain and Temperature Monitoring in Rigid Pavements

Current pavement survey protocols adopted by airport authorities mainly rely on non-destructive testing techniques and visual inspections. Although effective in quantitatively assessing the structural condition of paved assets, these approaches present several limitations: they do not enable direct, real-time measurement of the superstructure’s reactive behavior under thermal and/or mechanical loading; they lack spatial and temporal consistency due to inspections being scheduled around operational constraints; and they offer limited capability for synergistic integration of data derived from multiple inspection sources.

To address these limitations, this study evaluates the reliability of an alternative structural health monitoring (SHM) system embedded within the primary load-bearing concrete layer of rigid pavements. Specifically, Fiber Bragg Grating (FBG) optical sensors are employed to simultaneously measure strain and temperature in a scaled concrete slab. The main objective is to assess the mechanical and thermal performance of both bare and transduced fiber optic sensors bonded to the bottom surface of the slab.

First, a static bending test conducted at constant temperature on the instrumented laboratory specimen demonstrates sensor durability and good agreement with corresponding numerical simulations. Subsequently, a uniform thermal gradient test on the free slab highlights the sensors’ high responsiveness and produces results consistent with the expected elastic thermal expansion of concrete, while also revealing material limitations related to thermal conductivity and inertia. Finally, a thermal deconvolution algorithm is applied to compensate for temperature-induced wavelength shifts, allowing the isolation of mechanically induced strains.

Overall, the proposed SHM system represents a promising and viable preliminary alternative for real-time monitoring of mechanical load conditions and thermal gradients in rigid pavements, which are increasingly challenged by rising traffic demands and extreme climate conditions.