Effect of carbonation on transport properties of cementitious materials under different environmental conditions: A pore-scale modelling

Abstract

CO₂ treatment of cementitious materials has been suggested as a potential approach to reduce carbon footprint and improve material properties. To gain a deep understanding of carbonation mechanism and evaluate its effect of transport properties, a pore-scale diffusive-reactive lattice model is proposed in this study considering multiple environmental factors and materials conditions. Based on the regenerated microstructure and governing equations, the coupled effects of saturation degree and temperature on the carbonation degree can be quantified. The evolution of pore structure is visually determined, which is governed by the competition between precipitation and dissolution for the combined carbonation and calcium leaching process. The relationships between microstructural changes and gas/solute transport properties are evaluated. The predicted and experimental data show an acceptable agreement. The results demonstrate that increasing carbonatable phase contents enhance CO₂ capture capacity, and carbonation degree reaches the maximum between saturation of 50% and 70%, and the optimal saturation degree is related to the peak pore radius. Carbonation under lower saturation and higher temperature can lead to significant densification of gel pores, which is crucial for reducing transport properties. The model also reveals that specific surface area, associated with the solid phase, plays a more dominant role in the carbonation process than porosity.