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The Study On Detection Technique Of Chloride Ion Concentration In Concrete Based On Optical Fiber Sensor

Posted on:2018-08-25Degree:MasterType:Thesis
Country:ChinaCandidate:G H SuFull Text:PDF
GTID:2348330542462651Subject:Photoelectron and photonics technology
Abstract/Summary:PDF Full Text Request
The corrosion of reinforced concrete structure is one of the most important problems in the field of civil engineering and public transportation.It is related to the service life and safety hidden trouble of the building structure.The traditional corrosion monitoring program for steel bars is based on the monitoring of the variables which is produced by the steel after the occurrence of the corrosion,and can't predict the starting point of the corrosion in advance.As the chloride intrusion is the main cause of corrosion of reinforced concrete structures,the monitoring of chloride ion concentration in concrete structures by fiber optic sensors can predict the corrosion degree of the reinforced concrete structures,and achieve the early detection when the steel bars just in contact with the chloride ions,which provided the possibility for predicting the occurrence of corrosion in advance before the occurrence of corrosion.The main work of this paper is summarized as follows:(1)The current status of concrete corrosion monitoring and the development of fiber refractive index sensor are investigated.Based on the relationship between the corrosion of steel bar and the concentration of chloride ion,the paper studies the technical scheme of monitoring the concentration of chloride ion in the concrete structure using fiber optic refractive index sensor,which provides a basis for the monitoring of the early corrosion degree of reinforced concrete.(2)A sensor for measuring chloride ion concentration gradient distribution in concrete structures is proposed based on the temperature and refractive index sensing characteristics of long-period fiber grating(LPFG).According to the coupled-mode theory,the sensing principle of LPFG is studied,and the sensing properties of LPFG for temperature and refractive index are analyzed.The measurement of chloride ion concentration gradient distribution of concrete structure is realized,and the chlorine ion concentration resolution is about 25 ~ 50 g/L,the temperature resolution is 0.8?.(3)A dual-parameter optical fiber sensor of temperature and chloride ion concentration is proposed based on the Sagnac ring with polarization-maintaining fiber(PMF)and LPFG.The influence of the birefringence effect induced by the embedded LPFG and PMF on the temperature and refractive index sensing properties of the Sagnac ring was investigated.According to the relationship between the refractive index and the chloride ion concentration,the resolution of chloride ion concentration is about 20 g/L and the temperature resolution is 0.04?.(4)A new type of high sensitivity chloride ion concentration detection sensor for concrete structure is proposed based on the sensing principle of the on-core fiber multimode interferometer.The sensing properties of the no-core fiber multimode interferometer for temperature and refractive index are studied.The feasibility of the high sensitivity sensing of the chloride ion concentration in the concrete structure with the no-core fiber multimode interferometer was verified by accelerated corrosion experiments,the resolution is about 6.5 g/L in which the measurement error of the chloride ion concentration caused by the temperature change is about 0.5(g/L)/?.
Keywords/Search Tags:Chloride Ion Concentration Detection, Refractive Index Fiber Optic Sensor, Reinforcement Corrosion, No-core Fiber Multimode Interferometer
PDF Full Text Request
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