Abstract
Steel corrosion resulting from the penetration of chloride ions or carbon dioxide is a major cause of degradation for reinforced concrete structures,. The objective of the present investigation was to develop a low-cost sensor for steel corrosion, which is based on a very simple physical principle. The flat end of a cut optical fiber is coated with an iron thin film using the ion sputtering technique. Light is then sent into a fiber embedded in concrete and the reflected signal is monitored. Initially, most of the light is reflected by the iron layer. When corrosion occurs to remove the iron layer, a significant portion of the light power will leave the fiber at its exposed end, and the reflected power is greatly reduced. Monitoring of the reflected signal is hence an effective way to assess if the concrete environment at the location of the fiber tip may induce steel corrosion or not. In this paper, first the principle of the corrosion sensor and its fabrication are described. The sensing principle is then verified by experimental results. Sensor packaging for practical installation will be presented and the performance of the packaged sensors is assessed by additional experiments.
Highlights
Reinforced concrete structures make up a large portion of the physical infrastructure of the world, and their durability is an issue of great concern
Within the alkaline environment of concrete, steel is in a passivated state, with a negligible corrosion rate, but when carbon dioxide and chlorides penetrate through the concrete cover to reach the steel, depassivation occurs and the corrosion rate becomes significant
We have presented a new fiber optic sensor for the detection of steel corrosion in concrete structures
Summary
Reinforced concrete structures make up a large portion of the physical infrastructure of the world, and their durability is an issue of great concern. One approach to assess the corrosion of steel is to measure the depth of carbonation or the chloride profile in the concrete structure. The conventional approach is to perform chemical analysis on samples cored from the concrete structure. The cored sample is further sliced into thin sections, and each section is ground into powder for chemical analysis. While this can provide an accurate chloride profile in the structure, a major limitation should be pointed out. Different researchers [3,4] have come up with different relations between the critical chloride concentration and pH As another major drawback, taking cores from a large concrete structure at critical locations is often difficult and costly. The coring operation can only be occasionally performed
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