For reinforced concrete structures, steel corrosion resulting from the penetration of chloride ions or carbon dioxide is a major cause of degradation. The objectives of the work are to develop a novel optical fiber sensor for steel corrosion and to introduce a novel approach for chloride prevention....[ Read more ]

For reinforced concrete structures, steel corrosion resulting from the penetration of chloride ions or carbon dioxide is a major cause of degradation. The objectives of the work are to develop a novel optical fiber sensor for steel corrosion and to introduce a novel approach for chloride prevention.

For the corrosion sensor, it is based on a very simple physical principle. The flat end of a cut optical fiber is coated with an iron thin film by 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 thesis, the principle of the corrosion sensor and its fabrication are first described. The sensing principle is then verified by experimental results. Sensor packaging for practical installation is presented.

For novel chloride control design, a series of holes are incorporated in the concrete cover. The holes are filled with circulating water to make their boundary free of chloride ions. When chloride ions penetrate into the concrete, most of the chloride ions are removed by water and the time for chloride concentration to reach the critical value is significantly increased. In this thesis, the concept of such an approach is first described. The feasibility of the principle is then verified by simulation results and a set of preliminary experiments.