Abstract
A multi-scale characterisation of the transport process within cementitious microstructure possesses a great challenge in terms of modelling and schematization. In this paper a numerical method is proposed to mitigate the resolution problems in numerical methods for calculating effective transport properties of porous materials using 3D digital images. The method up-scales sub-voxel information from the fractional occupancy level of the interface voxels, i.e. voxels containing phaseboundary, to increase the accuracy of the pore schematization and hence the accuracy of the numerical transport calculation as well. The numerical identification of the subvoxels that is associated with their level of occupancy by each phase is obtained by increasing the pre-processing resolution. The proposed method is presented and employed for hydrated cement paste microstructures obtained from Hymostruc, a numerical model for cement hydration and microstructure simulation. The new method significantly reduces computational efforts, is relatively easy to implement, and improves the accuracy of the estimation of the effective transport property.
Highlights
Transport processes in cementitious materials play a crucial role in both the degradation process of building materials as well as in the containment of hazardous wastes
Even when only considering a cement paste microstructure, the pore sizes cross at least four orders of magnitude (10 nm – 100 μm). When it comes to the description of transport processes in porous media, a parameter that is of paramount importance is the effective transport, e.g. diffusion, coefficient
The proposed method is tested by means of calculating the effective diffusion coefficient of virtual hydrated cement paste microstructures obtained from Hymostruc [5, 6]
Summary
Transport processes in cementitious materials play a crucial role in both the degradation process of building materials as well as in the containment of hazardous wastes. Even when only considering a cement paste microstructure, the pore sizes cross at least four orders of magnitude (10 nm – 100 μm) When it comes to the description of transport processes in porous media, a parameter that is of paramount importance is the effective transport, e.g. diffusion, coefficient. The model is limited to represent the microstructure of hydrated cement paste at levels smaller than the voxel size used, which affects the ability to describe the pore structure into a small detail. The proposed method is tested by means of calculating the effective diffusion coefficient of virtual hydrated cement paste microstructures obtained from Hymostruc [5, 6]. The method is general in nature that should be applicable to a diverse range of investigated porous medias, e.g. microstructures obtained by different numerical or experimental methods
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