Chloride Diffusivity Of Hardened Cement Paste From Multiscale Modeling

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Title: Chloride Diffusivity Of Hardened Cement Paste From Multiscale Modeling

Author(s): Pietro Carrara; Laura De Lorenzis and Tao Wu

Publication: Special Publication

Volume: 305

Issue:

Appears on pages(s): 6.1-6.10

Keywords: artificial microstructure; chloride binding; chloride diffusion; durability; homogenization; hardened cement paste; multiscale; numerical analyses; real microstructure

Date: 9/1/2015

Abstract:
The durability of concrete structures is particularly susceptible to aggressive environments, in particular to the penetration and diffusion of chloride ions. Hence, a reliable prediction of the chloride diffusivity is mandatory to schedule efficient maintenance as well as to estimate the service and ultimate life of concrete structures. This is a non-trivial task because the chloride diffusion process is clearly a multiscale problem since it is influenced by different factors acting at different length and time scales, including the ability of some phases of the hardened cement paste (HCP) to interact with chloride ions. In the present work the chloride diffusivity of HCP is numerically simulated using a modified version of Fick’s law accounting for the ability of some HCP phases to bind chloride ions. The 3D HCP microstructures for the analyses are generated artificially, using the software CEMHYD3D, as well as segmented starting from real X-ray images, and in all cases are discretized using a voxel-based mesh. The effective (homogenized) coefficient of diffusivity, to be used for mesoscale analyses, is obtained through upscaling and is validated using data from the literature. Finally, comparisons between real and artificially generated HCP microstructures are performed and discussed.