Application On Monitoring Of Steel Corrosion Based On Distributed Fiber Optic Sensing Technology

Reinforced concrete structure is one of the most widely used structures in civil engineering, which will also play a big role over a long period of time for the future. Steel corrosion is one of the most important reasons to cause decline of durability of concrete structures and premature destruction of concrete structures, which has caused great loss in the lives and property of the people. Monitoring of steel corrosion is a essential way to research steel corrosion, which has sufficiently significance to overcome the problem of steel corrosion and decline of durability of concrete structure.The purpose of this paper is to research monitoring of steel corrosion using fiber optic sensing technology. Enclosed this purpose, mechanism, process, modifying factors and existing monitoring technique of steel corrosion in concrete structures is introduced; Relationship between steel corrosion and durability of concrete structure is presented; Keystone of distributed sensing technology is explained, which is based on Brillouin scattering. Based on comprehending above, a novel kind of fiber optic sensor was proposed, which is used for monitoring of steel corrosion in concrete structures; The sensor, which is based on distributed sensing technology of Brillouin Optical Time-Domain Analysis (BOTDA) and the principle of the volume expansion of steel bar due to corrosion, measures hoop stress by corrosion expansion force and concludes the condition of steel corrosion; The sensor is encapsulated by cement mortar, which has higher survival ratio, longer service life and more accurate measurement result. Two type sensors were designed and made, uncushion sensor whose fiber optic coil was winded round steel bar and cushion sensor whose fiber optic coil was winded round cushion. And then sensors were embedded into concrete specimens, whose performance was researched concretely in electrochemical accelerating corrosion system.Experiment results show that the design of the sensor has high feasibility and practicability; Corrosion expansion strain can be measured consecutively in every sensor. Uncushion sensor has high sensitivity and small measurement range; Cushion sensor has large measurement range, which is able to adjust by cushion thickness; We reached the relationship between corrosion expansion strain and corrosion expansion force, damage degree of concrete by elasticity formulas. In conclusion, the fiber optic corrosion sensor can be used for corrosion monitoring and evaluation of durability of concrete structures, which has a significant contribution to the research of steel corrosion and durability of concrete structures.