What is concrete carbonation?

Carbonation of concrete is a natural process that occurs when carbon dioxide present in the environment reacts with water or retained moisture, reducing its pH.

For a concrete to be considered an alkaline medium that protects or passivates the reinforcement, it must have pH values of around 12-13. The reduction of the pH due to carbonation implies a loss of this protective capacity and, therefore, the corrosion process of the reinforcement is activated, always under the appropriate conditions.

Visible and structural causes of carbonated concrete

Over time, concrete begins the so-called carbonation process, although we are not aware of this phenomenon until the consequences start to become visible. An early discovery will allow the problem to be treated and solved at its root.

A thorough investigation is required to find out if carbonation has already started. In the case of needing an analysis with quick results, the most advisable way is to extract a piece, preferably from the damaged area, and analyse it.

Once we obtain the results, we will be able to know the degree to which the structure is affected and we will proceed to analyse the most appropriate treatment, always bearing in mind that this problem will not happen again.

Effects of concrete carbonation

The effect of carbonation is the oxidation of the reinforcement. This process causes an increase in their volume, causing internal stresses in the concrete structure in the form of fissures and cracks.

Oxidation of reinforcement

Before starting any treatment, we must be sure that the problem is a carbonation process. Once we have this clear, we will start with the phenolphthalein test, which is a pH indicator and depending on the degree we will be able to know in depth in what state of carbonation it is. If the pH of the element is higher than 9, it changes colour to pink, and if it is lower, the colour remains the same.

Concrete carbonation: The ideal solution to the problem

At Molins we have the best products for dealing with concrete carbonation: BETOPAINT FLEX elastic anti-carbonation paint is an elastic coating suitable for protecting concrete and mortar against carbonation. It is permeable to water vapour, allowing the substrate to breathe.

CORTEC MIC 2021 surface sealant, which uses a blend of reactive silicates, surface activating agents and migratory corrosion inhibitors to protect reinforced concrete against corrosion.

It stands out for its ability to delay the onset of the corrosion process while reducing the speed of corrosion, increasing the useful life of the reinforcement, for its easy application and because it is organic and environmentally friendly.

Finally, we have BETOPAINT, a coating for the protection of concrete and mortar against carbonation, developed on the basis of acrylic copolymers in aqueous dispersion, single-component, waterproof, with a decorative finish and resistant to atmospheric agents.

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