From ABC News in Science, 22 November 2016:
The production of cement is a major source of carbon dioxide, but new research suggests the material that makes up our concrete jungles also plays an important role in reabsorbing carbon emissions.
But as cement ages and weathers over time, it also absorbs carbon dioxide in a process called carbonation.
In a paper published today in Nature Geoscience, a team of researchers calculated that the carbonation process has offset as much as 43 per cent of the emissions associated with cement production, not including the emissions associated with fossil fuel use during cement production, over the past 70 years. Read more.