CO2 Absorption

Recent research confirms that the carbonation of concrete is a mechanism that counters much of the CO2 emissions resulting from the original manufacture of cement.* Upon exposure to air, concrete and concrete masonry have the potential to absorb (sequester) atmospheric CO2.

Concrete’s absorption of CO2 can occur either through the use of CO2 curing technologies in the manufacture of pre-cast concrete products, or as a natural carbonation process that takes place over time.  In both cases, the fundamental mechanism for CO2 absorption is carbonation, which occurs during the service life of a structure and particularly after demolition.  Even highly durable concrete with low permeability will sequester CO2 rapidly when the structure is eventually demolished and recycled.

Traditionally, the carbonation of concrete has been associated with negative issues such as alkalinity loss and corrosion of reinforcement.  However, these issues can be easily dealt with by appropriate design.

As carbonation has the potential to reduce the net CO2 emissions of cement-based materials, it should be considered in life cycle analyses, and will also have a significant effect on the criteria for environmental labeling of cement-based materials.

Further international and New Zealand-based study is still required to accurately quantify the carbonation of concrete as a mechanism to mitigate CO2 emissions.  However, the concept that the world’s concrete infrastructure could provide the single largest human-made carbon sink has genuine scientific merit.

*Danish Technological Institute. CO2 uptake during the concrete life cycle. (2007)