Carbonation of concrete
Carbonation is the absorption of CO2 during the lifecycle of the product. In whole-life terms, this reduces the CO2 footprint of concrete (and other materials containing cement).
The speed of absorption depends on a number of factors including the type of concrete and the surrounding environment. Lightweight blocks and low strength concrete recarbonate relatively quickly. High strength concrete takes longer, with most of the recarbonation occurring later in its lifecycle i.e. after demolition and crushing, due to the increase in surface area.
For more information on Carbonation, read the article by Tom De Saulles, published in CONCRETE (April 2013). Reproduced with permission from CONCRETE magazine.