Advances in Computed Tomography for Geomaterials: GeoX 2010

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

K. Krabbenhoft — M.R. Karim

Centre for Geotechnical and Materials ModellingUniversity of Newcastle, NSW, [e-mail]

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 has previously been developed and is here applied to a variety of cement paste whose microstructure has been digitized to a resolution of 1 µm. With this resolution, important sub-micron 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.

 

KEYWORDS: X-ray microtomography, cement paste, homogenization, numerical methods.

1. Introduction

The transport properties of cement pastes are of crucial importance to the durability of much of our civil infrastructure. Due to its corrosive effects and abundance in many natural environments, considerable efforts have been made to quantify particularly the transport of chloride. To date, most research has been concerned with the diffusive transport through fully saturated cement pastes and a number of specialized testing methods for evaluating the effective diffusivity have been developed (Tang and Nilsson 1992; Friedman ...