Extraction of Effective Cement Paste Diffusivities from X-ray Microtomography Scans

Abstract

The problem of extracting effective diffusivities of cement pastes on the basis of X-ray microtomography images is considered. A general computational homogenization framework is developed and applied to a variety of cement pastes whose microstructure has been digitized to a resolution of 1 µm. At this resolution, important submicron features are not resolved. Consequently, we propose a methodology whereby the pore space is ascribed a diffusivity less than the free diffusivity. For this purpose, a simple rule that incorporates microtomography data is proposed and shown to yield satisfactory results.

New Renormalization Schemes for Conductivity Upscaling in Heterogeneous Media

“…No-flow b. c. P 0 P 1 in an 'effective' conductivity that falls in between these two bounds Karim and Krabbenhoft 2010;Ostoja-Starzewski and Schulte 1996). Considering the approximate nature of renormalization, the use of mixed boundary conditions thus appears to be quite reasonable.…”

Evaluation of Microstructure and Transport Properties of Deteriorated Cementitious Materials from Their X-ray Computed Tomography (CT) Images

“…However, there have been some studies indicating some degree of anisotropy in microstructure, particularly from images obtained from X-ray microtomography [22,26,27]. It is also imperative to understand the presence of structural anisotropy in damaged cement matrix as discussed in [28,29,30].…”

Permeability determination of porous media using large‐scale finite elements and iterative solver

“…Recent advances in X‐ray microtomography (XMT) enables us full 3D characterization of internal microstructure of the medium in sufficient details . XMT has been applied to an increasing range of materials including cement‐based materials , sandstone , and soils . In this paper, we aim to predict the permeability of sand whose 3D real microstructure has been generated from the XMT.…”

“…Even though the stabilized FE system becomes symmetric and positive definite, it still poses a challenge for achieving reliable and efficient solution especially for large‐scale problems. For large‐scale 3D simulation of permeability through porous microstructure, the iterative solution technique is an obvious choice due to its relatively small memory footprints and in some instances its excellent efficiency for computational homogenization problems . It is well established that iterative solvers have to be used with some form of preconditioning to be effective on challenging problems.…”

“…The virtual testing is carried out by the increasingly popular XMT and a computational homogenization framework. The computational homogenization procedure is derived from authors' earlier work and is extended here for upscaling for effective permeability of the medium. Equal order FE formulation is used, and the nodal block diagonal preconditioner is implemented to use with the traditional CG iterative solver.…”