Prototype polymer optical fibre sensors for reinforced concrete monitoring

Prototype polymer optical fibre Bragg grating (POFBG) sensing devices were developed for continuous in-situ monitoring of reinforced concrete. The POFBG sensors were fabricated using optical fibres with a CYTOP core and XYLEX overcladding and embedded onto 16-mm reinforcing bars with three distinct embedding designs. One prototype measures in-situ temperature and relative humidity, which are key parameters for assessing concrete quality and durability from its initial curing through prolonged periods. The other two prototypes monitor the bond strength between the concrete and reinforcing bars, a critical property for preventing structural failure. Reinforcing bar pull-out tests demonstrated the sensors' capability to detect early interfacial debonding, known as bond slip, between the reinforcing bar and the surrounding concrete. The prototype sensors presented in this work are compact, robust, and highly sensitive, showing promising results for early-stage failure detection in reinforced concrete structural health monitoring applications.