Carbonation of concrete : Evaluation of CO2 uptake of Benders Sverige AB concrete products and landfills

The cement industry accounts for 5-7% of the global emissions of carbon dioxide, where CO2 is mainly emitted during the calcination process. However, CO2 is also absorbed by all concrete products during their lifetime through the process of carbonation. Based on a carbonation calculation model, this project investigated the CO2 uptake by Benders Sverige AB products and landfills.Benders Sverige AB produces mainly paving stones and roof tiles. During the years 2011-2020, more than 56,000 tonnes of CO2 were permanently absorbed by Benders’ products in use. This uptake corresponds to 9% of calcination emissions released during cement production. Roof tiles stand for >77% of the CO2 uptake, which is most likely due to their high surface to volume ratio, which facilitates carbonation. Furthermore, roof tiles are surrounded by air whereas paving stones are mostly carbonated from their topside.It was also investigated how surface treatments affect the carbonation of roof tiles. A phenolphthalein test showed that surface treatments generally reduce carbonation, but since roof tiles are also carbonated from their underside it is possible that even surface treated roof tiles will be fully carbonated during their service life.To calculate the CO2 uptake of a concrete landfill, a hypothetical scenario was set up. The calculations show that there is a big potential in the optimisation of landfills to increase carbonation and therewith decrease the CO2 net emissions of Benders Sverige AB