The CO2 uptake of concrete in a 100 year perspective

More than 50% of the CO2 emitted during cement production originates from the calcination of limestone. This CO2 is reabsorbed during the life cycle of cement based product such as concrete and mortars in a process called carbonation.The impact that concrete carbonation has in the assessment of CO2 emissions from cement production has not been fully documented. Specifically, there is a lack of knowledge about the carbonation of demolished and crushed concrete. The existing models for calculating carbonation do not take into account what takes place after the concrete has been demolished. Consequently, the contribution of the cement and concrete industry to net CO2 emissions may be significantly overestimated.This paper encompasses theoretical work, laboratory studies, surveys and calculations based on the concrete production in the Nordic countries of Denmark, Iceland, Norway and Sweden. The estimated CO2-uptake through carbonation of the concrete produced in the year 2003 seems during a 100 year period to amount to a significant proportion of the CO2 emitted by calcination of the raw mix used to produce the Portland cement used in the concrete.