Non-destructive evaluation of chloride-induced corrosion in reinforced concrete

Non-destructive evaluation of chloride-induced corrosion in reinforced concrete: Electrochemical impedance spectroscopy sheds new light on generally applied sensors performance

Pargar, F. (TU Delft Materials and Environment)
Koleva, D.A. (TU Delft Materials and Environment)
Koenders, E.A.B. (TU Delft Materials and Environment)
van Breugel, K. (TU Delft Materials and Environment)

2014

Service life of reinforced concrete structures exposed to chloride enriched environment is well known to be mainly determined by steel passivity breakdown in the event of chloride-induced corrosion initiation and propagation. Since Cl- induced (localized) corrosion is caused by the free (water-soluble) chloride, present in the pore network of a reinforced concrete structure, quantifying the level of free chloride locally, e.g. via embedded Ag/AgCl electrodes (chloride sensors), is a generally accepted and applicable approach to monitor the time to corrosion initiation. The measurement is essentially a potential (voltage) reading over time and as such logically depends, among other factors, on the electrical and microstructural properties of the surrounding medium. Therefore, an accurate determination of the time to corrosion initiation significantly depends on the properties of relevant interfaces, such as the steel|cement paste interface and/or the Ag|AgCl|cement paste interface. In this paper, steel rods were coupled with Ag/AgCl sensors and embedded in cement paste cylinders. The specimens were immersed in simulated pore solution, containing 855 mM chloride concentration. Electrochemical impedance spectroscopy (EIS) was employed for quali-/quantification of the corrosion process on the steel surface (medium to low frequency response), while simultaneously providing information for the electrical properties of the bulk cement-based matrix through the high frequency response. The open circuit potential (OCP) values of both sensors and steel rods were recorded for more than 30 days. The results show a good agreement between sensor readings and steel electrochemical response i.e. time to corrosion initiation was recorded via steel OCP readings, whereas the relevant chloride content was estimated via the sensors’ OCP readings.

http://resolver.tudelft.nl/uuid:e6cb0aa2-ecaa-4b77-8ea1-4ee8c6cac4ee

6WCSCM, Barcelona, Spain

6th edition of the World Conference of the International Association for Structural Control and Monitoring, 2014-07-15 → 2014-07-17, Edificio Vèrtex, Universitat Politècnica de Catalunya, Barcelona, Spain

Institutional Repository

conference paper

© 2014 F. Pargar, D.A. Koleva, E.A.B. Koenders, K. van Breugel