Corrosion of steel bars induced by accelerated carbonation in low and high calcium fly ash geopolymer concretes

• Ca content influences the durability of class F fly ash geopolymer concretes.
• Low-Ca class F fly ash geopolymer concrete is suitable for structural applications.
• High risk of corrosion in high-calcium class F fly ash geopolymer concretes.

Reinforced geopolymer concretes prepared using three fly ashes of varying Ca content were subjected to accelerated carbonation for a period of 450 days. Changes induced in the concretes were determined after exposure to a 5% CO2 atmosphere, and electrochemical measurements were performed over the time of testing to evaluate the effects of carbonation on the corrosion process of the steel rebars. This study indicates that geopolymer concretes prepared with fly ashes having reduced calcium content are more suitable for the production of durable concrete for structural applications under exposure to carbonating environments, as the properties of these materials seem to mitigate the risk of carbonation-induced reinforcement corrosion in concrete.