Tapered Polymer Optical Fiber Sensors for Monitoring the Steel Bar Corrosion

The reinforcement corrosion detection has received considerable attention in the field of structural health monitoring (SHM) due to the rising awareness about the safety and longevity of reinforced building structures particularly the steel bars. In this study, we propose a corrosion-monitoring device based on a tapered polymer optical fiber sensor (TPFS) for steel bars. The sensing principle of the proposed sensor was based on the corrosion expansion law and the attenuation loss equation to the transmitted light. In the test, TPFS with three different taper diameters were characterized in the separate accelerated corrosion test with a steel bar immersed in the 3.5 wt% NaCl solution. Experimental results show that each TPFS had a unique characteristic response corresponding to the increasing corrosion products that build up around the steel bar. In addition, the sensitivities of three types of TPFS were compared in terms of the two stages, and results indicated that the sensor with 0.6 mm tapered size would be an ideal alternative for corrosion monitoring of steel bars.