As I understand on date, there is no carbon neutral or carbon negative concrete mix design available, as all concrete contains cement. The production of one tonne of cement emits nearly the same amount of carbon dioxide in the atmosphere. It is interesting to know that fresh concrete absorbs some of that CO2 back during carbonation which takes place during the setting and hardening process. One effective way to reduce the carbon footprint of concrete is to minimise the use of cement, partially replacing it with the mineral admixtures like fly ash, blast furnace slag, rice husk ash, which are industrial and agricultural wastes. These admixtures, besides giving long term strength to concrete also enhance its durability.
