Realkalisation

Realkalisation is a method used to stop and permanently prevent reinforcement corrosion in carbonated concrete structures by increasing their pH to a value greater than 10.5, which is sufficient to restore and maintain a passive oxide film on the steel.

Realkalisation involves a technique whereby a current is passed through the concrete to the reinforcement by means of an externally applied anode, which is attached temporarily to the concrete surface. A paste of sprayed cellulous fibre with a solution of potassium or sodium carbonate is used as the electrolyte covering the concrete surface.

The net effect of realkalisation includes it's effect on the concrete and on the steel reinforcement. The alkaline solution is transported into the concrete mass under the influence of the low voltage electrical current. This raises the concrete pH level to greater than 10.5. With regard to the effect on steel reinforcement, the alkalinity is increased at the steel surface by production of hydroxyl ions. This reinstates the dense passive film on the steel, which protects from further corrosion.

The realkalisation process requires minimal repair work of the concrete, especially the need to break out concrete behind the reinforcement, which is in itself a noisy, dusty and expensive exercise. The realkalisation process takes approximately one week to complete.

Key features of this technology are:

  • Environmentally friendly: Major reduction of concrete breakout.
  • Low maintenance: In comparison to patch repair and coating.
  • Long term global protection: Provides effective treatment for the entire area of application.
  • Proven technology: Long history of satisfactory performance.

Our recommended application:

  • Carbonated structures where permanent long term repair solution is required.
  • Carbonated structures where removal of concrete behind the reinforcement, which is essential for traditional repair, is not a viable option for structural reasons.

Standards: 

Electrochemical realkalisation and chloride extraction treatments for reinforced concrete  CEN / TS 14038-1.

Standard Practice: Electrochemical realkalisation and chloride extraction treatments for reinforced concrete. NACE SP0107-2007.