Enhancing sustainability: integrating carbon dioxide into Portland cement concrete

The concrete industry, which heavily relies on Portland cement, contributes to about 5–8% of the global CO2 emissions on its own. This research aims to investigate the feasibility of permanently capturing CO2 within concrete. The captured CO2 is expected to undergo a reaction with the unhydrated components, resulting in the conversion of CO2 into nano-sized calcium carbonate particles in situ. To achieve this objective, different cement mixtures were prepared, incorporating carbon dioxide in the form of gas and dry ice at various dosages. The freshly produced concrete was evaluated for its properties, including slump, slump retention, temperature, unit weight, and air content. The hardened concrete properties were assessed through tests measuring compressive and flexural strength, as well as chemical resistance. Additional important tests were conducted, such as scanning electron microscopy (SEM), pH measurement, rapid chloride permeability test (RCPT), and energy-dispersive X-ray spectroscopy (EDX). The potential use of CO2-incorporating mortar mixtures as fast-setting mortar was also explored. This study successfully demonstrated the feasibility of incorporating CO2 and producing high-quality concrete. It also suggests the possibility of injecting other gases into concrete when appropriate. Recommendations are provided for future research endeavors, as well as for the concrete industry, to further contribute to a green and sustainable environment.