Issue 24, 2022

Drained and undrained heat capacity of swelling clays


In microporous materials, poromechanical drained (open pore) and undrained (close pore) conditions play a role in the thermo-mechanical properties, which can also be affected by specific ion effects. Heat capacity is a key property to understanding the thermo-hydro-mechanical behavior of clays. However, there is a lack of bottom-up approaches aiming at capturing the influence of confined water and ion effects on the heat capacity of clays. We perform molecular dynamics simulations to obtain the heat capacity of Na- and Ca-montmorillonite using classical and semi-classical approaches. The heat of adsorption is computed from Grand Canonical Monte Carlo (GCMC) simulations under ambient conditions. We provide the theoretical framework to compute the drained heat capacity using the undrained heat capacity and the heat of adsorption. The semi-classical approach is required to capture the heat capacity of the solid mineral but cannot properly capture that of the inter-layer electrolyte. A hybrid approach is proposed, which combines the semi-classical approach for the mineral and the classical approach for the electrolyte. The undrained and drained heat capacities of clays evolve linearly with the water content, which leads to the conclusion that the effects of the mixing of hydration states are not significant. Undrained heat capacity is almost independent of the counterion nature. In contrast, the overall trends of drained heat capacity plotted against the water content exhibit larger values for Na-Mmt than for Ca-Mmt. Our results are in agreement with experimental data for a variety of smectites.

Graphical abstract: Drained and undrained heat capacity of swelling clays

Supplementary files

Article information

Article type
25 Mar 2022
03 May 2022
First published
24 May 2022
This article is Open Access
Creative Commons BY license

Phys. Chem. Chem. Phys., 2022,24, 15003-15014

Drained and undrained heat capacity of swelling clays

T. Honorio and L. Brochard, Phys. Chem. Chem. Phys., 2022, 24, 15003 DOI: 10.1039/D2CP01419J

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

Read more about how to correctly acknowledge RSC content.

Social activity