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Carbonation is an atmospheric process that degrades concretes, especially reinforced concrete. This phenomenon exposes steel reinforcement and causes resistance problems due to corrosion on reinforced concrete structures. Here are some explanations to better understand the process of carbonation of concrete...

What is the carbonation of concrete?

Corrosion of structures is the main cause of degradation of reinforced concrete. Carbon dioxide - or CO2 - present in the atmosphere, enters the concrete surface and reacts with the products resulting from the hydration of the cement. Carbonation then progressively modifies the chemical composition and the internal structure of the concrete.

Everything happens during the manufacture of concrete. More concretely, when pouring concrete, the pH is high which leads to the formation of a layer of iron hydroxide around the reinforcements. It is a protective layer (passivation layer) that prevents corrosion. But the reaction of CO2 in the air with the concrete components can lead to a decrease in this pH: so-called carbonation reaction. Corrosion begins at this precise moment.

Moisture, rain, CO2 concentration, temperature are all important factors in the rate of carbonation.

The consequences of carbonation of concrete

The carbonation of concrete is a phenomenon that degrades reinforced concrete. In particular, she is responsible for exposing their steel frames.

Carbonation causes problems over the life and strength of concrete structures. The steel bars swell under the effect of corrosion and burst the concrete coating. The steels are then exposed and continue to corrode.

This carbonation effect is studied and researched by CSEC and CRIC.

What preventive measures against carbonation?

Recommendations have been specified in the standard NBN EN 206-1 and its Belgian supplement, standard NBN B 15-001. These standards provide information on the required cement content and are supplemented by the standard NBN EN 1992-1-1 relating to the coating of reinforcement. All the elements and figures are given in order to produce a quality concrete and perennial.

The study conducted by CSEC and the CRIC has shown that the type of cement plays a role in the particle size of the concrete. These questions are very technical, it is important to contact a professional mason. This building expert will answer all your questions...

Video Instruction: Carbonation – The eventual killer of reinforced concrete