Carbonation
The slow reaction of atmospheric carbon dioxide with the alkaline compounds in concrete, which lowers its pH. Concrete protects steel by being alkaline, so as the carbonation front reaches the reinforcement, that protection is lost and corrosion can start.
On an actual building
It is the main mechanism behind deterioration in older inland buildings. Carbonation depth is measured with a phenolphthalein indicator, and comparing it against the cover depth tells you how close a member is to trouble.
What we most often have to correct
That a building looks fine so the concrete is fine. Carbonation is invisible and advances for decades before anything appears on the surface.
Terms that come up alongside this one
- Cover Meter
An instrument that locates reinforcement and measures the depth of concrete cover over it, without breaking out..
- Chloride Attack
Corrosion of reinforcement driven by chloride ions penetrating the concrete, typically from sea air, sea spray or brackish groundwater.
- Anti-Carbonation Coating
A coating with high resistance to carbon dioxide diffusion, applied to concrete to slow the advance of the carbonation front while still allowing water vapour out..
More deterioration terms
Carbonation — questions we get asked
What does carbonation mean in waterproofing?
The slow reaction of atmospheric carbon dioxide with the alkaline compounds in concrete, which lowers its pH. Concrete protects steel by being alkaline, so as the carbonation front reaches the reinforcement, that protection is lost and corrosion can start.
Why does carbonation matter on a real project?
It is the main mechanism behind deterioration in older inland buildings. Carbonation depth is measured with a phenolphthalein indicator, and comparing it against the cover depth tells you how close a member is to trouble.
What do people commonly get wrong about carbonation?
That a building looks fine so the concrete is fine. Carbonation is invisible and advances for decades before anything appears on the surface.
Have a building showing this?
If a term on this page describes something you are looking at, a site inspection will tell you how far it has gone and what it needs. It costs nothing.
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