The Influence of Fly Ash Carbonation on the Protective Properties of Concrete Cover Towards Reinforcement

Abstract

To address the challenge of reducing carbon dioxide emissions, this study focuses on carbon dioxide sequestration in calcareous fly ash and its use in mortar and concrete specimens, including reinforced structures. Calcareous fly ash was used in this study because it contains more reactive Ca phases, enabling efficient CO2 capture and long-term storage through mineral carbonation. The research examines the influence of incorporating carbonated fly ash on the protective properties of the concrete cover for steel reinforcement, along with an analysis of the mechanical behavior of the specimens, resistance to weathering carbonation, and the modeling of the service life of reinforced concrete structures. The results indicate that the compressive strength of concrete specimens decreases with the addition of carbonated ash, though by no more than 9% after 90 days. The carbonation rate of concrete increases with the addition of ash; however, a roughly 4% lower rate was observed for carbonated ash compared to non-carbonated ash. No significant impact of ash carbonation on chloride diffusion or the corrosion process of reinforcement in mortars was detected. As a result, the estimated service life of concrete containing both ash and carbonated ash is over 20 times longer than that of the reference concrete.