Modeling of Carbonation based on Thermo-Hygro Physics with Strong Coupling of Mass Transport and Equilibrium in Micro-pore Structure of Concrete

Carbonation of concrete is a phenomenon that causes corrosion of steel in reinforced concrete structures, and is recognized as an important problem for ensuring the durability of structures. Against this background, many researchers have proposed methods for predicting the progress of concrete carbonation under various environments. In this study, the authors aim to improve the accuracy and to extend the applicable range of existing models, not only for controlled acceleration environments, but also for low concentrations such as the carbon dioxide concentration in the atmosphere, and for various temperature histories, taking into account the application of the thermodynamic model to actual structures. From reaction equations (1) and (2), the consumption and generation of the following equivalent masses can be obtained: calcium hydroxide and C-S-H gel consumption, calcium carbonate, silica gel, and water generated at an arbitrary temperature condition. At an arbitrary stage during carbonation, the volume of each of these can be calculated in accordance with the Relational expression of mass and volume. The change in volume of hydrated products due to carbonation was obtained as the volumetric difference between the sum of calcium carbonate and generated silica gel and the sum of calcium hydroxide and consumed C-S-H gel. Figure 1 shows the concept of the change in porosity in the 2. Modeling of carbonation based on thermo-hygro physics with strong coupling of mass transport and equilibrium in micro-pore structure of concrete