5. Glossary

Carbonation; Carbonation

Over time, the hydrates formed from the reaction of cement and water, in particular portlandite crystals (Ca(OH) ₂ ), naturally carbonate on contact with atmospheric carbon dioxide dissolved in capillary water according to the carbonation reaction: Ca(OH) ₂ + CO ₂ ⇒ CaCO ₃ + H ₂ O.

Under ambient conditions of temperature and relative humidity, carbonation is governed by the transport of atmospheric CO ₂ within capillary water. It begins at the extreme surface of the concrete and progresses towards the core of the material. Note that hydrated calcium...