Cathodic Protection

Freyssinet, Inc., as principal contractor, undertakes installation, associated repair work, and application of coatings. Clients benefit by not having numerous relationships with a variety of inter-dependent sub-contactors, the responsibility for successful project implementation is clearly defined.


The Problem

Reinforcement corrosion is the major cause of deterioration of concrete structures. Good quality concrete provides a highly alkaline surrounding to steel reinforcement. If this alkalinity reduces, the reinforcement becomes increasingly susceptible to corrosion. The expansive forces caused by corrosion and rust formation are sufficient to cause concrete to crack and spall, leading to a need for concrete repair. There are two main mechanisms that cause concrete deterioration: Carbonation and Chloride Attack. Carbonation is caused by atmospheric carbon dioxide, which dissolves in water to form carbonic acid. This acid progressively penetrates and reacts with concrete, reducing the pH value from 13 to 9; at the reinforcement layer, the steel is de-passivated, and begins to corrode. De-icing salts, seawater and marine aggregates are common sources of chlorides. Where chlorides are able to penetrate down to the reinforcement layer they will aggressively attack the steel, starting corrosion. The rate of both carbonation and chloride attack depend on concentration of carbon dioxide in the atmosphere / chlorides at the concrete surface, concrete permeability / density, and concrete moisture content. Cracked or poor quality concrete will deteriorate faster.

The Solution

Conventional patch concrete repairs to damaged concrete are unlikely to be successful where carbonation has progressed behind the reinforcement layer, or where chlorides remain in sufficient concentration in adjacent untreated concrete. Cathodic protection, which works by passing a small electric current through the reinforcement layer, has several significant advantages over other available techniques: it is a continuous process that both stops existing corrosion and prevents future attack, it is a permanent ongoing solution that does not require reapplication, it is suitable for severely damaged concrete, it is effective against both carbonation and chloride attack, its effectiveness can be controlled and monitored, and it is more economic than complete replacement. It is particularly suited to highway and marine structures where re-contamination is likely.

Foreva® solutions can be used to control the progression of corrosion of reinforcements in reinforced concrete structures at all of its stages of development by:

• Preserving a protective environment around the reinforcement
• Stopping the corrosion initiation process in the reinforcements
• Preventing the progression of corrosion in the long term after repairing the structural damage it has caused
  
  Foreva® solutions work on the area surrounding the steel or on the reinforcements themselves by:
• Treating the facing to slow down or stop the penetration of pollutants before they reach the reinforcement
• Depolluting the coating to restore the protective environment around the reinforcements
• Protecting the reinforcements by means of an electrochemical process to stop the corrosion, without acting on the spread of the pollution.
     

  Foreva® GP Zinc

Areas of Application:
Repair