An investigation on the three-dimensional transport of chloride ions in concrete based on X-ray computed tomography technology

In order to demonstrate the three-dimensional chloride ions diffusion in real concrete, the X-ray CT technique was applied to reconstruct the meso- and micro-structure of concrete. An improved threshold method was used to eliminate the noise during X-ray CT images processing. The special distribution of aggregate particles and pores were recognized and analyzed based on the reconstructed meso-structure of real concrete. The reconstructed meso-structure, as well as the interfacial transition zone (ITZ) were introduced into a multi-phase model to numerically characterize the three-dimensional diffusion of chloride ions in real concrete. And the simulation results were verified through electron probe technique. A parameter sensitivity analysis was conducted to furtherly assess the influence of ITZ diffusivity on the chloride ions diffusion in concrete. This investigation indicates that aggregate particles tends to deposit at the bottom of the specimen and the pores are likely to concentrate at the top part. Due to the special distribution of aggregate particles and pores, the chlorides ions diffuse more quickly at the bottom of the specimen. The study proves that the aggregate particles, pores and ITZ are of great importance for the three-dimensional chloride ions diffusion in real concrete. (C) 2019 Elsevier Ltd. All rights reserved.