As mchannon comments, concrete does not absorb a significant amount of CO2 as it cures. I was mistaken. The calcium in lime forms silicates.
However, it remains true that half of the life cycle emissions of concrete come from fossil combustion. Replacing fossil combustion with other energy sources can cut concrete's CO2 footprint in half without any major changes in concrete's composition or use.
However, it remains true that half of the life cycle emissions of concrete come from fossil combustion. Replacing fossil combustion with other energy sources can cut concrete's CO2 footprint in half without any major changes in concrete's composition or use.