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Case Study

Arousa Island Bridge

Arousa is a small island of 7km² in the middle of Ria de Arousa. Most of the 5000 inhabitants work in the fishing and mussel industry. It is connected to the mainland by a 1980m single-cell box girder and prestressed concrete road bridge which was completed in 1985.






October 2010



Arousa Island Bridge - icon problem

The Problem Identified

Over the years marine salts had caused steel corrosion in the piers.

Arousa Island Bridge - icon solution

The Solution Developed

The speed of application of concrete repairs was very important to the client due to the tidal movements around Arousa Island Bridge. CPT designed a DuoGuard hybrid anode system and over 7700 DuoGuard 500 anodes were installed in the majority of the piers. Some anodes were placed with an underwater embedding mortar DuoCrete UW, specially formulated to stay in place when installed underwater.

Using an external power source, an impressed current was applied to stop active corrosion and render the steel passive. The DuoGuard anodes were then disconnected from the power source to self-generate a galvanic current, sufficient to maintain steel passivity and control corrosion.

MN15 Reference Electrodes were installed to facilitate monitoring of the corrosion control system. The enclosed service duct which ran the length of the bridge, housed the anode and steel connections, relatively easily accessible for test purposes or future impressed current application if required.

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The Benefits Provided

Corrosion related deterioration of Arousa Island Bridge has been halted. After the initial power up period using an external power source the DuoGuard system is self-powered thus minimising future maintenance requirements and associated life costs.

Arousa Island Bridge - arousa bridge v2017
Steel corrosion in the piers


Arousa Island Bridge - duoguard v2


DuoGuard™ Hybrid Anode halts reinforced concrete corrosion for targeted protection.

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Arousa Island Bridge - mn15 v2


MN15 Reference Electrode, Manganese Oxide electrode for monitoring structures.

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