Carbon Footprint of Concrete Buildings seen in the Life Cycle Perspective

Article by Claus V. Nielsen, Danish Technological Institute.
Published in Proceedings NRMCA 2008 Concrete Technology Forum, June 2008, Denver

Abstract
The Danish cement and concrete industry has worked hard to reduce the environmental footprint of concrete for the past 15 years. The use of supplementary cementitious materials is normal procedure on almost every concrete plant. Especially fly ash is added extensively for all types of concrete applications.

The primary environmental indicator is still the CO2 footprint when concrete is assessed and compared with other structural designs. However, even though concrete is known to have a relatively high CO2 emission during production it is of paramount importance to include the service life of buildings in this type of calculations. The thermal mass of concrete helps improve the energy performance of a building which again will reduce the effect of a high initial CO2 footprint. A slight difference in the energy performance of a building design may tip the balance from an environmentally sound design to the direct opposite in terms of energy performance. After end of service life concrete is suitable for recycling back into construction applications. Furthermore, the concrete rubble will carbonate and absorb CO2 from the atmosphere.

The paper will demonstrate these issues through examples where the benefits of heavy building materials are illustrated. The inherent high thermal mass of con¬crete is used to improve the energy performance of buildings as well as the thermal comfort compared with light weight materials.