In this paper, a novel kind of method to monitor corrosion expansion of steel rebars in steel reinforced concrete structures named fiber optic coil winding method is proposed, discussed and tested. It is based on the fiber optical Brillouin sensing technique. Firstly, a strain calibration experiment is designed and conducted to obtain the strain coefficient of single mode fiber optics. Results have shown that there is a good linear relationship between Brillouin frequency and applied strain. Then, three kinds of novel fiber optical Brillouin corrosion expansion sensors with different fiber optic coil winding packaging schemes are designed. Sensors were embedded into concrete specimens to monitor expansion strain caused by steel rebar corrosion, and their performance was studied in a designed electrochemical corrosion acceleration experiment. Experimental results have shown that expansion strain along the fiber optic coil winding area can be detected and measured by the three kinds of sensors with different measurement range during development the corrosion. With the assumption of uniform corrosion, diameters of corrosion steel rebars were obtained using calculated average strains. A maximum expansion strain of 6,738 με was monitored. Furthermore, the uniform corrosion analysis model was established and the evaluation formula to evaluate mass loss rate of steel rebar under a given corrosion rust expansion rate was derived. The research has shown that three kinds of Brillouin sensors can be used to monitor the steel rebar corrosion expansion of reinforced concrete structures with good sensitivity, accuracy and monitoring range, and can be applied to monitor different levels of corrosion. By means of this kind of monitoring technique, quantitative corrosion expansion monitoring can be carried out, with the virtues of long durability, real-time monitoring and quasi-distribution monitoring.
References
[1]
Bentur, S.; Diamond, N.S. Berke, Steel Corrosion in Concrete: Fundamentals and Civil Engineering Practice; E & FN Spon: London, UK, 1997.
[2]
Broomfield, J.P. Corrosion of Steel in Concrete; E & FN Spon: London, UK, 1997.
[3]
Gonzalez, J.A.; Feliu, S.; Rodriguez, P. Threshold steel corrosion rates for durability problems in reinforced structures. J. Corros 1997, 53, 65–71.
[4]
Schiessl, P. Corrosion of Steel in Concrete, RILEM Technical Committe 60-CSC; Chapman & Hall: New York, NY, USA, 1988.
[5]
Elsener Corrosion of Steel in Concrete. In Corrosion and Environmental Degradation; Schutze, M., Ed.; Wiley-VCH: Weinheim, Germany, 2000; Volume II, pp. 389–436.
[6]
Ahmad, S. Reinforcement corrosion in concrete structures, its monitoring and service life prediction—A review. Cem. Concr. Compos 2003, 25, 459–471.
[7]
Tang, L.P. Calibration of the Electrochemical Methods for the Corrosion Rate Measurement of Steel in Concrete. NORDTEST Project; No.1531-01,; 2007.
[8]
Martínez, I.; Andrade, C. Examples of reinforcement corrosion monitoring by embedded sensors in concrete structures. Cem. Concr. Compos 2009, 31, 545–554.
[9]
Qiao, G.F.; Ou, J.P. Corrosion monitoring of reinforcing steel in cement mortar by EIS and ENA. Electrochim. Acta 2007, 52, 8008–8019.
[10]
Li, H.; Ou, J.P.; Zhou, Z. Applications of optical fibre bragg gratings sensing technology-based smart stay cables. Opt. Lasers Eng 2009, 47, 1077–1084.
[11]
Glisic, B.; Inaudi, D.; Casanova, N. SHM Process as Perceived Through 350 Projects. Proceedings of the 2010 SPIE Smart Structures and Materials / NDE Symposium, Paper 7648-26, San Diego, CA, USA, 7–11 March 2010.
[12]
Inaudi, D.; Glisic, B. Long-range pipeline monitoring by distributed fiber optic sensing. J. Press. Vessel Technol 2010, 132, 011701:1–011701:9.
[13]
Ansari, F. Fiber optic health monitoring of civil structures. Smart Mater. Struct 2005, 14, doi:10.1088/0964-1726/14/3/001.
[14]
Ohno, H.; Naruse, H.; Kihara, M.; Shimada, A. Industrial application of the BOTDR optical fiber strain sensor. Opt. Fiber Technol 2001, 7, 45–64.
[15]
Murayama, H.; Kageyama, K.; Naruse, H.; Shimada, A. Distributed strain sensing from damaged composite materials based on shape variation of the Brillouin spectrum. J. Intel. Mater. Syst. Struct 2004, 15, 17–25.
[16]
Fuhr, P.L.; Huston, D.R.; McPadden, A.J. Embedded chloride detectors for roadways and bridges. Proc. SPIE 1996, 2719, 229–237.
[17]
Bennett, K.D.; McLaughlin, L.R. Monitoring of corrosion in large steel structures using low cost optical fiber sensors. Proc. SPIE 1995, 2446, 71–82.
Bao, X.; DeMerchant, M.; Brown, A.; Bremner, T. Strain Measurement of the Steel Beam with the Distributed Brillouin Scattering Sensor. Proceedings of the Health Monitoring and Management of Civil Infrastructure Systems, Newport Beach, CA, USA, 6–8 March 2001; Chase, S.B., Aktan, A.E., Eds.; 4337, pp. 223–233.
Horiguchi, T.; Kurashima, T.; Tateda, M. Tensile strain dependance of Brillouin frequency shift in silica optical fibers. Photon. Technol. Lett 1989, 1, 107–108.
[22]
Kurashima, T.; Sato, M. Measurement of strain distribution in structures using optical fiber. JSCE J 1997, 82, 18–20.
[23]
Bao, X.Y.; Zou, L.F.; Yu, Q.R.; Chen, L. Development and Applications of the Distributed Temperature and Starin Sensors based on Brillouin Scattering. Proceeding of the Optical Fiber Sensor, Vienna, Austria, 24–27 October 2004.
[24]
Fellay, A.; Thevenza, L.; Perez Garcia, J.; Facchini, M.; Scandale, W.; Robert, P. Brillouin-based temperature sensing in optical fibres down to 1 k. Proceedings of 15th Optical Fiber Sensors Conference Technical Digest, Ofs 2002, Portland, USA, 10 May 2002; pp. 301–304.
[25]
Horiguchi, T.; Shimizu, K.; Kurashima, T.; Tateda, M.; Koyamada, Y. Development of a distributed sensing technique using Brillouin scattering. J. Lightwave Technol 1995, 13, doi:10.1109/50.400684.
