A comprehensive ionic reaction model for mineral carbonation in the cement industry

This thesis develops a comprehensive ionic reaction model to examine mineral carbonation processes in supplementary cementitious materials, addressing a significant opportunity to reduce carbon dioxide emissions from the cement industry. The work focuses on the complex reaction kinetics and transport phenomena involved when cementitious materials interact with CO₂ in aqueous environments. The research introduces an innovative ionic reaction model that effectively captures physicochemical processes, including calcium leaching from supplementary cementitious materials, CO₂ dissolution and carbonate speciation reactions, solid surface reaction, and calcium carbonate precipitation. Unlike traditional shrinking core or two-film models, this approach explicitly accounts for the evolution of solution chemistry and the dynamic interplay between reaction kinetics and diffusion limitations. Parameter estimation was conducted using various optimization techniques (Genetic Algorithm, Differential Evolution, and a hybrid approach), with the model demonstrating excellent agreement with experimental measurements of calcium hydroxide consumption, pH evolution, and calcium carbonate formation. The analysis revealed three distinct kinetic regimes during carbonation: an initial reaction-limited phase dominated by Ca(OH)₂ dissolution, a transition phase with competing mechanisms, and a final diffusion-limited phase controlled by transport through precipitated layers on the particles. The model provides valuable insights into carbonate speciation dynamics, the relative contributions of different calcium sources to carbonation, and the progressive development of diffusion barriers. These findings establish a foundation for optimizing carbonation processes in supplementary cementitious materials, potentially enabling more efficient CO₂ utilization in the cement industry and contributing to decarbonization efforts through carbon mineralization.

This thesis develops a comprehensive ionic reaction model to examine mineral carbonation processes in supplementary cementitious materials, addressing a significant opportunity to reduce carbon dioxide emissions from the cement industry. The work focuses on the complex reaction kinetics and transport phenomena involved when cementitious materials interact with CO2 in aqueous environments. The research introduces an innovative ionic reaction model that effectively captures physicochemical processes, including calcium leaching from supplementary cementitious materials, CO₂ dissolution and carbonate speciation reactions, solid surface reaction, and calcium carbonate precipitation. Unlike traditional shrinking core or two-film models, this approach explicitly accounts for the evolution of solution chemistry and the dynamic interplay between reaction kinetics and diffusion limitations. Parameter estimation was conducted using various optimization techniques (Genetic Algorithm, Differential Evolution, and a hybrid approach), with the model demonstrating excellent agreement with experimental measurements of calcium hydroxide consumption, pH evolution, and calcium carbonate formation. The analysis revealed three distinct kinetic regimes during carbonation: an initial reaction-limited phase dominated by Ca(OH)₂ dissolution, a transition phase with competing mechanisms, and a final diffusion-limited phase controlled by transport through precipitated layers on the particles. The model provides valuable insights into carbonate speciation dynamics, the relative contributions of different calcium sources to carbonation, and the progressive development of diffusion barriers. These findings establish a foundation for optimizing carbonation processes in supplementary cementitious materials, potentially enabling more efficient CO₂ utilization in the cement industry and contributing to decarbonization efforts through carbon mineralization.