Brighton Marina was constructed from reinforced concrete, precast circular hollow caissons with cast in-situ deck and superstructure. Completed in 1976 it was, at the time, the largest man-made marina in Europe. Marine structures are generally designed so that there is no significant maintenance for the first 50 years. That time was approaching and in 2004, HOP were charged with the mammoth task of assessing the existing condition of reinforced concrete work and developing a strategy of how to manage the breakwater in a sustainable way into the future.
Concrete has an inherent passivity that protects embedded steel reinforcement from corrosion. When a salt laden atmosphere penetrates reinforced concrete, this protective environment can break down over time. This effectively results in an electro chemical process with some areas becoming anodic and others becoming cathodic. This process results in the corrosion of embedded steel reinforcement at the anode and subsequent breaking up of concrete, leading to further and more rapid deterioration. Breaking out affected concrete and repairing in-situ is an almost impossible option for Brighton Marina, due to the highly exposed, tidal nature of the works and much of the work being permanently underwater. An alternative solution had to be found.
After extensive research throughout the UK and Europe, it was felt that some sort of electrical protection might be the answer. HOP ran several trials looking at a variety of sacrificial anode and impressed current protection systems. The most economic solution proved to be embedded sacrificial anodes inside the caissons protecting lower permenantly submerged areas with a system of impressed current to protect the higher level superstructure. This technique has been used in buildings and it is often now incorporated in new work, but has never been retrofitted on such a scale as this anywhere in the world.
As a result of our research HOP are working at the leading edge of advanced reinforced concrete rehabilitation, ensuring the protection afforded by the breakwaters at Brighton Marina can be sustained for the next 50 years and beyond.