Speaker
Description
Moisture transfers in clayey soils or earthen construction materials play an essential role on the integrity of the structures and the regulation of humidity of the environment. Concentrated clay systems are nanoporous materials through which moisture transfers can involve vapor or liquid water transport. Here, with the help of NMR relaxometry and MRI allowing to distinguish the different liquid populations in the medium, we provide a detailed description of the different stages of extraction of water from a compacted clay sample during drying. Free water is extracted first at a constant rate, driven by capillary effects. In the next stage the moisture transport results from the flow of adsorbed water films, along with vapor transport through the porosity and exchanges between the two populations, a scheme somewhat similar to that presented for cellulosic materials [1]. We show that the transport diffusion coefficient of the adsorbed water films alone may be determined through drying experiments of the sample with its porosity filled with oil, while the water vapor diffusion coefficient may be determined from the permeability to ethanol vapor (i.e., with limited interactions with the solid phase). The total moisture transport can then be described by a diffusion equation with a diffusion coefficient depending on these two coefficients and the sorption curve. This model, relying on parameters determined from independent tests, finally appears to well describe the characteristics of standard drying tests. The tools developed in this work can be generalized to any solid clayey system, the main parameters of the model varying with the porosity and clay type.
Reference
[1] Y. Zou, B. Maillet, L. Brochard, and P. Coussot, Unveiling moisture transport mechanisms in cellulosic materials: Vapor vs. bound water, PNAS nexus 3, pgad450 (2024)
| Country | France |
|---|---|
| Green Housing & Porous Media Focused Abstracts | This abstract is related to Green Housing |
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