MIT researchers used Raman confocal microscopy to observe the chemical reactions that happen when CO2 is injected into cement paste. They discovered a three-stage process where CO2 first captures calcium, then a silica gel network forms and later reacts to produce calcium silicate hydrate (C-S-H), the binding phase in cement. This distributed formation of C-S-H leads to a stronger, more uniform microstructure, with 13 percent higher compressive strength at 24 hours in CO2-injected samples compared to conventional mixes. The study, published in the Journal of the American Ceramic Society, provides the first direct visualization of these transient reactions. Understanding this mechanism opens the door to optimizing CO2 injection in concrete, which could potentially offset up to 40 percent of cement production emissions. The research was conducted at the MIT Concrete Sustainability Hub in collaboration with CarbonCure Technologies and IIT Jodhpur.
