Keywords: Concrete carbonation, Reaction and diffusion models
We present some mathematical models of concrete carbonation in Portland cement. The main novelty of our approach is to describe the intermediate chemical reactions, occurring in the carbonation process of concrete, involving the interplay of carbon dioxide with the water present into the pores. Indeed, the model here presented, and proposed in [1], besides describing transport and diffusion processes inside the porous medium, takes into account both fast and slow phenomena as intermediate reactions of the carbonation process. We also considered a further reaction: the dissolution of calcium carbonate under an acid environment. As a result, a trend inversion in the evolution of porosity can be observed for long exposure times. Such an increase in porosity results in the accessibility of solutions and pollutants within the concrete leading to an higher permeability and diffusivity thus significantly affecting its durability.
Also a simplified free boundary problems has been introduced in [2], which describe the evolution of calcium carbonate stones under the attack of CO2 dispersed in the atmosphere, taking into account both the shrinkage of concrete and the influence of humidity on the carbonation process. Some numerical simulations here presented are in substantial accordance with experimental results taken from literature.
References
Bretti G., Ceseri M., Natalini R., Ciacchella M.C., Santarelli M.L., Tiracorrendo G., A forecasting model for the porosity variation during the carbonation process, GEM - International Journal on Geomathematics, 2022, https://doi.org/10.1007/s13137-022-00204-7
Bretti G., Ceseri M., Natalini R., A moving boundary problem for reaction and diffusion processes in concrete: carbonation advancement and carbonation shrinkage. Discrete and Continuous Dynamical Systems Series S (2022), 15(8): 2033-2052. https://doi.org/10.3934/dcdss.2022092