Modeling of Multi-Physics Processes in Reinforced Concrete Carbonation Process Using Finite Difference Method: Numerical Aspects and Critical Revision

Predicting the service life of reinforced concrete structures is essential, as carbonation significantly compromises durability by triggering reinforcement corrosion. This paper provides a critical review of multi-physics numerical models designed to simulate the carbonation process, analyzing their mathematical formulations, assumptions, and governing parameters. Beyond the state-of-the-art review, this study implements a Finite Difference Method (FDM) solution for a widely cited coupled model to perform a focused parametric analysis. The results quantitatively demonstrate that the initial diffusivity of carbon dioxide is the dominant factor in carbonation depth. Crucially, the study investigates the "size effect" in massive concrete elements, revealing that thicker structures (> 1.0 m) exhibit significantly slower carbonation rates due to an internal moisture reservoir effect. By combining a theoretical synthesis with original numerical insights, this work offers practical guidance for improving service life predictions in large-scale infrastructure.