Effective diffusivity of cement pastes from virtual microstructures

Role of gel porosity and capillary pore percolation

Journal article (2018)

Authors

R.A. Patel Universiteit Gent, Belgian Nuclear Research Centre
Janez Perko Belgian Nuclear Research Centre
Diederik Jacques Belgian Nuclear Research Centre
Geert De Schutter Universiteit Gent
G. Ye Universiteit Gent, Materials and Environment - CEG
K. van Breugel Materials and Environment - CEG
Research Group
Materials and Environment (CEG) (TU Delft)
Cement paste Transport properties Microstructure modelling Diffusivity
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Published Date

20-03-2018

Language

English

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Faculty

Civil Engineering & Geosciences

Department

Materials- Mechanics- Management & Design

Research Group

Materials and Environment

Abstract

The role of capillary pores percolation and gel pores are investigated to explain the underlying differences between relative diffusivity obtained from different experimental techniques using microstructures generated from two different types of hydration model viz., CEMHYD3D (a voxel based approach) and HYMOSTRUC (a vector based approach). These models provide microstructures with different capillary pore connectivity for the same degree of hydration and the same porosity due to the underlying assumptions. In order to account for a C-S-H diffusivity at the micro-scale, a continuum micro-mechanics based model has been proposed. These simulations show that deperolation of capillary pores at around 20% of capillary porosity is essential in order to correctly predict diffusivity of cement paste with water-cement ratio by mass (w/c) in between 0.4 and 0.5. Furthermore from our analysis we present a viable postulate that the higher diffusivity measured by electric resistivity compared to other methods is due to differences in contribution from gel pores. For electrical resistivity measurement it is proposed that all gel pores are diffusive whereas for ion and tracer transport it is proposed that only nitrogen accessible gel pores are diffusive.