(600a) From Benchtop to Field Demonstration: Scaling the “CO2concrete” Technology for the Manufacture of Concrete Products By Carbon Dioxide Mineralization

Carbon capture and utilization processes that exploit “CO₂ mineralization” reactions to produce concrete products offer a transformative platform for gigaton-scale CO₂ utilization, globally, due to the vast market for concrete (> 20 billion tons, ~ $1 trillion annually). The reaction of portlandite (Ca(OH)₂), an archetypal alkaline solid, with carbon dioxide (CO₂) is one of such reactions that can be exploited to produce cementation agents with a low embodied-carbon intensity. This process is the core of the CO₂Concrete technology, which is supported by detailed investigations into the effects of reaction temperature, relative humidity (RH), and CO₂ concentration on the carbonation of portlandite in the form of finely divided particulates and monolithic compacts, and of the influences of pore saturation and CO₂ diffusivity on the carbonation kinetics and strength evolution of portlandite-enriched composites (“mortars").

Special focus is paid to uncover the factors affecting the extent of reactant (i.e., Ca(OH)₂) conversion in relation to the process conditions, moisture state (i.e., the presence of molecular or condensed water), and the size and surface area-to-volume ratio (SA/V, mm^-1) of monoliths. Notably, the carbonation of portlandite is not limited by surface passivation of reactants with products; rather, reaction progress is limited by the mobility of adsorbed water. Scaling from particulates to monolithic components, the imposition of a porous microstructure (through which CO₂ must diffuse prior to reaction) induces secondary conversion limits related to blocking of pore networks by condensed water. Further, the carbonation kinetics of monoliths are strongly linked to the rates of moisture transport and vaporization/condensation. Reducing saturation increases the gas diffusivity, and carbonation kinetics, so long as saturation exceeds a critical value (S_w,c ≈ 0.10); independent of microstructural attributes.

The outcomes of these bench-scale investigations are foundational to the scaleup of the CO₂Concrete process for operation in a field demonstration setting i.e., in a system using flue gas from actual coal-fired power plants to produce construction-ready prefabricated concrete products. The design of the CO₂Concrete process to produce masonry products from coal flue gas is described, considering aspects of site operations, materials handling, reaction kinetics, and integration into the flue gas source (host site). Built on a rigorous foundation of experimental and modeling investigations, the CO₂Concrete technology is scaling up rapidly, with the aim of realizing large-scale, economical, and efficient utilization of CO₂ emissions.