Natural carbonation of uncracked and cracked concrete: Sensitivity of regional geographical variations on the CO2 uptake-to-emissions ratio compared to global estimates

Abstract

CO2 uptake in concrete due to natural carbonation is increasingly becoming a pivotal part of the effort towards understanding and achieving net-zero emissions in the cement and concrete sector by 2050. This study aims to estimate CO2 uptake and CO2 uptake-to-emission ratio (%) of concrete over a 50-year service life exposed to natural carbonation. The key scenarios include variations in: Canadian geographic locations; environmental climate data; concrete mix designs (with and without supplementary cementing materials); sheltered/exposed concrete conditions; and cracked/uncracked concrete. Overall, based on the model estimates of scenarios in this study, the CO2 uptake-to-emission ratio (%) for all 12 selected locations are generally lower than the 20–25 % reported in national and international cement and concrete roadmaps and action plans aiming for carbon neutrality by 2050. Although uncracked and cracked concrete containing 50 % slag can achieve between ∼20–30 % CO2 uptake-to-emission ratio, it should be noted such a mix design scenario has potential to have reinforcement corrosion and/or de-icer scaling concerns leading directly to structural safety-related vulnerabilities.