Concrete carbonation poses a significant threat to the integrity of reinforced concrete structures. When exposed to the atmosphere, concrete undergoes a chemical process in which carbon dioxide, moisture, and calcium hydroxide react to form calcium carbonate. This reaction lowers the alkalinity of concrete, weakening the protective passivation layer around the steel reinforcements.
How does reinforcement Corrosion Occur?
The carbonation process is influenced by several factors, including the porosity of the concrete, humidity levels, carbon dioxide concentration, and the presence of moisture. Generally, carbonation advances at a rate of 1mm to 5mm per year, depending on the porosity and permeability of the concrete. As the concrete carbonates, its pH level decreases from around pH12 – 13 to approximately pH9, leaving the steel vulnerable to corrosion.
The corrosion of steel reinforcements leads to expansion and cracking within the concrete. Rust, which is formed as a result of the corrosion process, occupies up to six times the volume of the original steel. This expansion exerts pressure on the surrounding concrete, causing cracks and spalling.
Treating concrete carbonation involves several approaches depending on the severity and extent of the carbonation. Here are some common methods:
Protective Coatings:
Applying suitable coatings or sealers to the concrete surface creates a barrier. This helps slow down or minimize the carbonation process.
Alkaline Reagents:
Restoration of alkalinity is possible by applying alkaline reagents like sodium hydroxide or potassium hydroxide solutions to the carbonated concrete surface. These reagents react with carbon dioxide, converting it back to calcium carbonate and raising the pH level.
Concrete repair:
In cases where carbonation has caused significant damage to the concrete, repair becomes necessary. This involves removing and replacing the carbonated sections with new concrete and applying suitable repair materials to restore structural integrity.
It is important to emphasize that treating concrete carbonation requires expertise and should be carried out by experienced professionals who understand the specific conditions and appropriate repair techniques.
Regular inspection and maintenance play a crucial role in identifying early signs of carbonation and addressing them promptly. It is important to note that evaluating corrosion in concrete is a specialized task that may require the expertise of structural engineers, corrosion specialists, or material testing laboratories. These professionals can provide a comprehensive assessment and recommend appropriate repair and mitigation strategies based on the findings. Contact us today to learn more about our comprehensive services!
