MIT study visualizes how CO2 injection rewires cement chemistry for stronger, lower-carbon concrete

A new MIT study published in the Journal of the American Ceramic Society directly observed for the first time how injecting carbon dioxide into fresh cement paste alters its chemistry. Using Raman confocal microscopy, researchers tracked a three-stage reaction: CO2 first captures calcium to form carbonates, then a transient silica gel network forms and spreads throughout the paste, and finally that gel reacts to produce calcium silicate hydrate (C-S-H) distributed more evenly than in conventional cement. This uniform distribution leads to 13 percent higher compressive strength at 24 hours for paste with 1 percent CO2 by cement weight. The findings explain why CO2-injected concrete gains strength faster and offer a pathway to optimize the process for carbon storage. Theoretically, the method could offset up to 40 percent of cement production emissions, though practical offsets will be lower. Understanding the mechanism allows researchers to control the reaction and push for better performance, making this a significant step for low-carbon construction materials.