Problems encountered in the detection of reinforcement corrosion in concrete tunnel linings – theoretical considerations

✍ Scribed by J. Gulikers

• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: German
• Weight: 286 KB
• Volume: 54
• Category: Article
• ISSN: 0947-5117
• DOI: 10.1002/maco.200390097

✦ Synopsis

Abstract

For concrete structures in which oxygen availability is limited, the potentials recorded for passive steel reinforcement may be considerably more negative than −350 mV versus CSE. This situation may occur for concrete linings of bored tunnels located in water saturated soil. In view of the great practical importance of correct interpretation of results from potential mapping for durability assessment, the influence of oxygen availability on the steady state potential of passive steel has been investigated on a theoretical basis. For values of the ratio between thickness, d, to the oxygen diffusion coefficient D~Ox~ of the concrete cover approaching a critical value of 3.36 · 10^6^/(A~st~ · i~pas~), the potential will demonstrate a dramatic drop amounting to several hundreds of millivolts. Consequently, in this critical region of d/D~Ox~, the corrosion potential of steel in its passive state may vary over a wide range, and commonly used potential criteria to identify the actual electrochemical condition are not applicable. A numerical analysis using a simplified approach has been performed on the typical reinforcement arrangement of a tunnel lining. The analysis clearly demonstrates that the presence of 2 layers of passive steel located at different depths will result in a pronounced effect on the potential recorded at the inner concrete surface, thus hindering correct interpretation.