ABSTRACT
A CP system for protection of steel in concrete basically consists of a conductor called the anode from which a small direct current flows through the concrete to the reinforcement, see Figure 1. The steel potential becomes more negative and corrosion is suppressed. The anode can be either directly applied to the concrete surface (e.g., a conductive coating) or consists of a mesh of activated titanium
1 INTRODUCTION
Corrosion of reinforcing steel in concrete structures may occur, e.g., in bridges due to penetration of chloride ions from de-icing salts or sea water spray [Bertolini et al., 2004]. Reinforcement corrosion causes concrete cracking and steel diameter reduction eventually resulting in loss of safety. Conventional repair means heavy, labour intensive and costly work. Economic pressures (time and money) work against the required quality level (perfect steel cleaning, removal of contaminated concrete). Consequently, conventional repair is short lived in many cases. Corrosion reappears quickly and structures need to be repaired again after a relatively short time, further increasing life-cycle cost. In a European study of the life of repairs (mainly patch repair), it was found that repairs had a short life in practice [Tilly & Jacobs 2007]. A completely different situation comes about with cathodic protection (CP) as a repair method. Cathodic protection of reinforcing steel has been applied to concrete structures with corrosion damage in Europe for about 25 years [Grefstad 2005, Nerland et al., 2007, Polder 1998, Wenk & Oberhänsli 2007]. A recent study reports on long term performance of CP systems in UK motorway structures [Christodoulou et al., 2010].
