Every exposed concrete surface is absorbing CO2 from the air…even at this very moment.
Concrete is a carbon sink, and through a natural process called carbonation, concrete permanently sequesters CO2.
In fact, for all the concrete produced in the U.S. between 1990 and 2018, more than 300 million metric tonnes of CO2 will be absorbed and sequestered by concrete over its service life.
The Carbon Uptake Cycle
Cement is the key ingredient in concrete – the material that we see all around us – and the production of cement releases CO2. Cement is mixed with water and aggregates and hardens to form concrete. As a part of the curing process, calcium hydroxide is formed in the concrete.
Concrete is a porous material, like a sponge. CO2 is absorbed by any exposed concrete surface. When that CO2 reacts with the calcium hydroxide, it forms a mineral and the carbon is permanently captured.
This is carbon uptake.