Using Osmos FOS to Assess Corrosion Damage in RC Columns

Abstract

Fiber-Optic Sensors (FOSs) are being introduced in structural health monitoring of bridges and other structures as an alternative to conventional sensors such as electrical strain gauges and vibrating wires. Advantages of FOS, from a materials point of view, include resilience and durability. This study examines the viability of using Osmos FOSs to monitor corrosion-damage in scaled-down reinforced concrete columns. The test variables include the corrosion level, different rebar diameters and concrete covers. Five circular reinforced concrete (RC) columns were cast. The columns were 300mm (12 inch) in diameter by 900 mm (36 inch) long. Each column was reinforced longitudinally with 6 rebars (15M or 20 M or 25 M) and 10M stirrups were provided at 200mm (8 inch) o/c. The concrete cover was 30mm or 45mm or 60mm (1.25 inch or 1.75 inch or 2.15 inch). Accelerated corrosion technique was used to corrode the longitudinal rebars in the columns up to 10% mass loss. The columns were instrumented with Osmos FOSs that were externally mounted around the column’s circumference to monitor the lateral deformation due to corrosion. In addition, corrosion crack widths on the column face were monitored during corrosion exposure. The test results showed that Farady’s law prediction works well for low corrosion levels (up to 5% mass loss) but not for high corrosion levels (10% mass loss) and that it becomes un-conservative as the rebar diameter increases. Corrosion expansion measured based on the Osmos FOS readings and the summation of crack widths across the circumference of the column showed very good correlation. It was found that the corrosion expansion increases as the rebar size increases at any corrosion level and that the corrosion expansion increases as the concrete cover increases at high corrosion level. Therefore, based on the findings of this study, Osmos FOSs can be used in the assessment and monitoring corrosion of steel reinforcement in reinforced concrete columns.