Feasibility study on corrosion monitoring of a concrete column with central rebar using BOTDR

Yijie Sun 1, Bin Shi 1, Shen-en Chen 2, Honghu Zhu1, Dan Zhang 1 and Yi Lu 1

1 School of Earth Sciences and Engineering, Nanjing University, Nanjing, China

2 Department of Civil and Environmental Engineering, University of North Carolina Charlotte, NC 28223, USA

(Received May 20, 2012, Revised March 1, 2013, Accepted March 4, 2013)

Smart Structures and Systems, Vol. 13, No. 1 (2014) 041-053

DOI:http://dx.doi.org/10.12989/sss.2014.13.1.041

Fulltext link: http://www.techno-press.org/?page=container&journal=sss&volume=13&num=1

Abstract. Optical fiber Brillouin sensor in a coil winding setup is proposed in this paper to measure the expansion deformation of a concrete column with a central rebar subjected to accelerated corrosion. The optical sensor monitored the whole dynamic corrosion process from initial deformation to final cracking. Experimental results show that Brillouin Optical Time Domain Reflectometer (BOTDR) can accurately measure the strain values and identify the crack locations of the simulated reinforced concrete (RC) column. A theoretical model is used to calculate the RC corrosion expansive pressure and crack length. The results indicate that the measured strain and cracking history revealed the development of the steel bar corrosion inside the simulated RC column.

Keywords: rebar corrosion; expansion pressure; BOTDR; optical fiber; distributed sensing monitoring

1. Introduction

Steel corrosion is one of the predominant factors for the degradation of steel reinforced concrete (RC) structures especially for structures exposed to aggressive environments. Corrosion of steel rebar is considered negligible when it is fully surrounded by the alkaline environment of concrete. However, corrosion can be introduced during penetration of chloride ions and carbon dioxide. To quantify the rate of corrosion, electro-chemical methods such as corrosion potential, AC impedance, half-cell and linear polarization methods have been suggested (Andrade et al. 2002, Cheng et al. 2004, Hussain et al. 2001, Ismail et al. 2006, Poursaee et al. 2009). However, most of these methods are difficult to set up for in-situ monitoring.

Corrosion of rebars typically results in expansion of ferric materials which in turn induces straining to the surrounding concrete through volumetric expansion. This paper suggests using fiber optic sensors (FOS) to monitor corrosion process within RC structures. FOS technologies are attracting considerable interests due to the apparent advantages including their immunity to electromagnetic interference, their resistance to chemical attack and their high sensitivity and accuracy. Also due to the low cost of the sensors, FOS is ideal for rebar corrosion detection for a large coverage area.

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2. Working principle of BOTDR

3. Theoretical analysis of corrosion cracking

3.1 Calculation of crack length

3.2 Calculation of expansion pressure

4. Experiment

4.1 Materials and equipments

4.2 Specimen fabrication

4.3 Test procedure

5. Results and discussion

6. Conclusions

References

Andrade, C., Alonso, C. and Sarria, J. (2002), “Corrosion rate evolution in concrete structures exposed to the atmosphere”, Cement Concrete Comp., 24(1), 55-64.

Bao, X.Y. and Chen, L. (2012), “Recent progress in distributed fiber optic sensors”, Sensors, 12, 8601-8639.

Bao, X.Y., Dhliwayo, J., Heron, N., Webb, D.J. and Jackson, D.A. (1995), “Experimental and theoretical studies on a distributed temperature sensor based on Brillouin scattering”, J. Lightwave Technol., 7(7), 1340-1347.

Chen, D. and Mahadevan, S. (2008), “Chloride-induced reinforcement corrosion and concrete cracking simulation”, Cement Concrete Comp., 30(3), 227-238.

Cheng, Y.F. and Steward, F.R. (2004), “Corrosion of carbon steels in high-temperature water studied by electrochemical techniques”, Corros. Sci., 46(10), 2405-2420.

Leung, C.K.Y., Wan, K.T. and Chen, L. (2008), “A novel optical fiber sensor for steel corrosion in concrete structures”, Sensors, 8, 1960-1976.

Dantan, N., Habel, W.R. and Wolfbeis, O.S. (2005), “Fiber optic pH sensor for early detection of danger of corrosion in steel-reinforced concrete structures”, Proceedings of the Smart Structures and Materials 2005: Smart Sensor Technology and Measurement Systems, 274.

Ganesh, A.B. and Radhakrishnan, T.K. (2007), “Fiber-optic sensors for the estimation of pH within natural biofilms on metals”, Sensor. Actuat. B. - Chem., 123(3), 1107-1112.

Gao, J.Q., Wu, J., Li, J. and Zhao, X.M. (2011), “Monitoring of corrosion in reinforced concrete structure using bragg grating sensing”, NDT&E. Int., 44(2), 202-205.

Greene, J.A., Jones, M.E. and Duncan, P.G. (1997), “Grating-based optical fiber corrosion sensor”, Proc. SPIE, 3042, 260-266.

Habel, W.R. and Hofmann, D. (2007), “Fiber optic sensors for long-term SHM in civil engineering and geotechnique”, Proceedings of the International Society for Structural Health Monitoring of Intelligent Infrastructure Conference, Vancouver, Canada.

Hussain, R.R. (2001), “Underwater half-cell corrosion potential bench mark measurements of corroding steel in concrete influenced by a variety of material science and environmental engineering variables”, Measurement, 44(1), 274-280.

Huston, D.R. and Fuhr, P.L. (1998), Distributed and chemical fiber optic sensing and installation in bridges, Fiber Optic Sensors for Construction Materials and Bridges, (Ed. F. Ansari), 79-88.

Hu, W.B., Cai, H.L., Yang, M., Tong, X., Zhou, C. and Chen, W. (2011), “Fe-C-coated fibre Bragg grating sensor for steel corrosion monitoring”, Corros. Sci., 53(5), 1933-1938.

Ismail, M. and Ohtsu, M. (2006), “Corrosion rate of ordinary and high-performance concrete subjected to chloride attack by AC impedance spectroscopy”, Constr. Build. Mater., 20(7), 458-469.

Jiang, G., Wu, J. and Zhao, X.M. (2009), “Application of fiber Bragg grating sensor for rebar corrosion”, Proceedings of the SPIE 2nd International Conference on Smart Materials and Nanotechnology in Engineering, 749333.

Kurashima, T., Horiguchi, T. and Izumita, H. (1993), “Brillouin optical-fiber time domain reflectometry”, IEICE T. Commun., 4, 382-390.

Lam,C.C.C., Mandamparambil, R., Tong S., Grattan, K.T.V., Nanukuttan, S.V., Taylor, S.E. and Basheer, P.A.M. (2009), “Optical fiber refractive index sensor for chloride ion monitoring”, IEEE Sens. J., 9(5), 525 - 532.

Lee, I., Yuan, L.B., Ansari, F. and Hong, D. (1997), “Fiber-optic crack-tip opening displacement sensor for concrete”, Cement Concrete Comp., 19(1), 59-68.

Maalej, M., Ahmed, S.F.U., Kuang, K.S.C. and Paramasivam, P. (2004), “Fiber optic sensing for monitoring corrosion-induced damage”, Struct. Health Monit., 3(2), 165-176.

Poursaee, A. and Hansson, C.M. (2009), “Potential pitfalls in assessing chloride-induced corrosion of steel in concrete”, Cement Concrete Res., 39(5), 391-400.

Tang, J.L. and Wang, J.N. (2007), “Measurement of chloride-ion concentration with long-period grating technology”, Smart Mater.Struct., 16(3), 665-672.

Zhao, X.F., Gong, P., Qiao, J., Lu, J., Lv. X. and Ou, J.(2011), “Brillouin corrosion expansion sensors for steel reinforced concrete structures using a fiber optic coil winding method”, Sensors, 11, 10798-10819.

Zhao, Y.X., Yu, J. and Jin, W.L. (2011), “Damage analysis and cracking model of reinforced concrete structures with rebar corrosion”, Corros. Sci., 53(10), 3388-3397.