Results on the long-term performance and effectiveness of a galvanic CP system applied on a lightweight concrete bridge with prestressed steel as determined by depolarisation values and current densities

Vogel Cathodic Protection, Zwijndrecht, The Netherlands

Abstract

This paper gives insight in the research and investigations which were undertaken on a post tensioned light-weight concrete box girder bridge in the Netherlands. This project started in the first half of 2013 and measurements are still executed regularly. Due to long-term leakage of a longitudinal joint between 2 parts of the bridge, chlorides had penetrated into the concrete up to the level of the reinforcement and beyond, causing severe corrosion of the steel, spalling of the concrete cover and eventually causing danger for the shipping underneath the bridge due to falling lumps of concrete. To solve this problem, Galvanic Cathodic Protection (GCP) was applied in 2 stages. Firstly, in 2013, zinc based anode strips were applied on the soffit of 2 post tensioned lightweight bridge segments for the purpose of testing and monitoring. After obtaining good results from the test, in 2014/2015 the remaining 29 bridge segments were repaired and protected with the same GCP system as well. This paper reviews subsequent potential decay and current densities measurements, which have provided valuable information on GCP performance and throwing power. The results of anode performance at different locations and depths are reviewed. Concrete resistivity has shown a major influence on the effectiveness of the installed GCP system.