Fiber optic sensors enabled monitoring of thermal curling of concrete pavement slab: Temperature, strain and inclination

An intellectual system is developed to monitor concrete pavement slab subjected to external temperature fluctuations. Truly distributed fiber-optic temperature and strain sensors and an innovative Fabry-Perot interferometer-based optical fiber inclinometer are installed in the concrete pavement slab so as to monitor and evaluate its thermal curling process. The system is demonstrated to be effective in detecting the thermal curling of slab. The results substantiate that the top surface of the slab has a fast reaction rate to the heating/cooling process. The bottom surface temperature has a time-lag comparing to the top surface, which results in a sharp increase then a slow reduction in the top-vs-bottom temperature difference. In the light of the inclinometer, it is proven that the tilt angle of the curvature of the slab has a high degree of synchronization with the top-vs-bottom temperature difference. The temperature/strain distribution maps are also presented and uneven distributions of temperature and strain are captured. Moreover, taking the advantage of the multiplexing capacity of the distributed fiber-optic sensors, the coefficient of thermal expansion (CTE) of the slab can be easily obtained and used to feed a finite element model. Finally, a three-dimensional finite element model is established to completely understand the curling process measured from the monitoring system. The model and the experimental data agree well with each other. While the sensors output realistic temperature and deformations at certain locations, the validated model is able to reveal more details of the nonlinearity inside the slab.