Calculating CO_2 Uptake for Existing Concrete Structures during and after Service Life

摘要

This paper presents a model that can calculate the uptake of CO_2 in all existing concrete structures, including its uptake after service life. This is important for the calculation of the total CO_2 uptake in the society and its time dependence. The model uses the well-documented cement use and knowledge of how the investments are distributed throughout the building sector to estimate the stock of concrete applications in a country. The depth of carbonation of these applications is estimated using two models, one theoretical and one based on field measurements. The maximum theoretical uptake potential is defined as the amount of CO_2 that is emitted during calcination at the production of Portland cement, but the model can also, with some adjustments, be used for the other cement types. The model has been applied on data from Sweden and the results show a CO_2 uptake in 2011 in all existing structures of about 300000 tonnes, which corresponds to about 17% of the total emissions (calcination and fuel) from the production of new cement for use in Sweden in the same year. The study also shows that in the years 2030 and 2050, an increase in the uptake in crushed concrete, from 12000 tonnes today to 200000 and 500000 tonnes of CO_2, respectively, could be possible if the waste handling is redesigned.