Distributed fibre optic as sensor for corrosion detection of steel reinforcement

Abstract

Previous studies indicated that problems with the application of distributed fibre optic sensor remain unresolved despite considerable effort in the last few decades. This research describes the work conducted to develop the use of BOTDA, as a distributed strain sensing technology, to identify the presence of corrosion in steel reinforcement in concrete structures. BOTDA is capable of measuring relative strain at any point along a standard optical cable. A properly installed cable can replace multiple closely-spaced strain sensing gauges and is considered cost-effective in this context. In corrosion monitoring, the presence of corrosion can be monitored by many means such as fibre optic sensing technique. The application of distributed fibre optic in corrosion detection seems to be a potential for research. The location of corrosion in steel reinforcement in concrete is expected to be detected from the occurrence of spike in the relative strain profile obtained from a single optical fibre. There are many implementations that require careful consideration and hence are examined in this research. Specimens were casted and installed with standard fibre optic cables along the steel reinforcement. Reinforcement were grinded at predetermined locations to reduce its cross sectional area to simulate cavity due to corrosion. Relative strain profiles were obtained from BOTDA when the specimens are loaded. Further investigation is recommended to make better sense of the results obtained.