Durability evaluation of structural performance based on CO2 curing conditions

Recently, extreme weather events linked to global warming have increasingly impacted the construction industry. Global warming is primarily driven by carbon dioxide (CO2), methane, and nitrous oxide, with CO2 being the most significant contributor owing to fossil fuel combustion. Carbon capture, utilization, and storage (CCUS) has emerged as a key strategy in reducing CO2 emissions. Although CO2 has been conventionally viewed negatively in the construction sector owing to its association with corrosion in reinforced concrete, it can enhance mortar properties by reacting with calcium hydroxide during curing, forming calcium carbonate that densifies pores and improves strength. We investigated the performance of mortar cured under CO2 conditions to assess its feasibility before applying it to structural elements. We evaluated compressive strength, shrinkage strain, and durability using mercury intrusion porosimetry. Results show that mortars cured in a CO2 chamber exhibited compressive strengths approximately 1.7-2.1 times higher than those cured in a general chamber on days 3, 7, and 14. Additionally, total porosity decreased by nearly two-fold, enhancing material density. Rapid carbonation penetration was observed within the first 7 days, stabilizing subsequently, while higher initial shrinkage strains later stabilized. These findings suggest that CO2 curing enhances compressive strength and reduces porosity, demonstrating the potential for effective CO2 utilization and storage in construction materials. Furthermore, substituting ordinary cement with slag during mixing could yield dual CO2 reduction benefits, contributing to sustainable construction practices. This study provides foundational insights for advancing CCUS technologies and mitigating CO2 emissions in the construction industry.