CarboCat – Atomistic and Kinetic Monte Carlo Modeling of Surface-Catalyzed Carbonation Mechanisms on C-(A-)S-H and Portlandite Minerals

• Applicants: Mohammadreza Izadifar, Ph.D.; Neven Ukrainczyk, Ph.D.
• Subject Area: Construction Material Sciences, Chemistry, Building Physics
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 576002917

Carbonation processes in cementitious materials are key to improving CO₂ sequestration and concrete durability over time. To achieve this, a fundamental understanding bridging quantum-level atomistic carbonation mechanisms with mesoscopic kinetics via kinetic Monte Carlo (KMC) simulations is required. This project focuses on key calcium-alumino-silicate-hydrate (C-(A-)S-H) phases, including tobermorite 14Å and 11Å, its alumino-analogue, jennite, and portlandite (Ca(OH)₂), to elucidate surface-catalyzed carbonation pathways. Atomistic modeling will establish the surface reaction activation energies at transition states using the improved dimer method (IDM) combined with machine learning force fields (MLFFs). Reaction rates across diverse surface orientations will be computed using density functional theory (DFT), supported by vibrational frequency analyses via density-functional perturbation theory. To capture surface heterogeneity, distinct crystallographic orientations will be evaluated to determine surface energies and predict their contribution on the overall reaction rate. Individual atomistic reaction rates will be upscaled with kinetic Monte Carlo simulations to predict mesoscopic carbonation rates. Experimental validation at the mesoscopic scale will corroborate the simulations, providing novel insights into surface-specific carbonation kinetics. The findings provide new atomistic insights into the support the development of carbonation models to improve CO₂-enhanced concrete curing, wet carbonation of RCP suspensions or predict concrete durability. Keywords: cementitious materials, carbonation, CO2 sequestration and use, density functional theory (DFT), Kinetic Monte Carlo (KMC), surface carbonation rates, C-(A-)S-H, portlandite.

• DFG Programme: Research Grants
• Co-Investigator: Professor Eduardus Koenders, Ph.D.