Effects of crack and ITZ and aggregate on carbonation penetration based on 3D micro X-ray CT microstructure evolution

Previous researchers have made a lot of contributions on carbonation reaction. However, effects of multi-cracks and interfacial transition zone (ITZ) on the diffusivity of carbon dioxide are critical and thorny problems. In this study, numerical simulation of carbonation process using the COMSOL Multiphysics are presented based on in-situ 3D microstructure evolution of X-ray CT. Firstly, micro X-ray computed tomography (X-ray CT) was used to monitor the carbonation depth evolution of cement mortar with different additions of blast furnace slag (BFS). It is shown that the optimal addition of blast furnace slag (BFS) against the carbonation is no more than 50%. In addition, COMSOL Multiphysics numerical model based on micro X-ray CT image was used to investigate effects of transverse crack and interfacial transition zone (ITZ) on the diffusivity of carbon dioxide. Finally, effects of different crack width, length, ITZ of polygon Random Aggregate Structure (RAS), and aggregate size and content on the diffusivity of carbon dioxide have been investigated.