Research On Fiber Bragg Grating Sensors For Monitoring Corrosion Of Reinforcing Steel

Reinforced concrete has become the most widely used civil engineering structure because of its good plasticity,low cost and good integrity.Working in the dry,chlorine-free environment,reinforced concrete structure has good durability,but in seawater and other chloride environment,reingforcing steel is easy to be corroded.Steel corrosion leads to cracking and peeling of concrete cover,which reduces the adhesion between steel bars and concrete cover and the mechanical properties of steel bars.Rreinforcing steel corrosion is the primary factor in reducing the durability of reinforced concrete structures.It is an effective method to solve the problem of reducing the durability of reinforced concrete structures by monitoring the early corrosion of reinforcing steel and timely repairing and strengthening damaged members.In this paper,two kinds of corrosion sensors were designed,and performance of the sensors was studied in the electrochemical corrosion accelerating test.The main contents are summarized as follows:(1)Detection methods and monitoring technologies for reinforcing steel corrosion were reviewed,and the advantages and disadvantages of traditional detection methods and optical fiber corrosion sensors were summarized.(2)The basic structure and sensing principle of FBG were described in detail,and the formulas of strain and temperature of FBG were deduced.(3)Based on the principle of rust expansion and FBG strain increasing,an FBG sensor for monitoring reinforcing steel corrosion was designed.And its structure was improved based on test results.(4)Based on the principle of rust loss and FBG strain releasing,an FBG sensor for monitoring reinforcing steel corrosion under water was designed.And its structure was improved based on test results.(5)Based on the basic structure and working principle of the two FBG corrosion sensors,the calculation formulas of reinforcing steel corrosion rate were deduced.(6)The reasonable winding turns of FBG,the influence of concrete strength grades and steel corrosion speed on the performance of the sensors and the performance of the wrapped filter paper sensor were studied in the electrochemical corrosion accelerating test.