Water sorption isotherms and hysteresis of cement paste at moderately high temperature, up to 80 °C
File(s)
Published version
Author(s)
Type
Journal Article
Abstract
The constitutive models of concrete often consider water desorption isotherms to be near-equilibrium and
significantly affected by moderately high temperature, 40–80◦C, typically through microstructural changes.
However literature data suggest that adsorption, not desorption, is near-equilibrium and moderate temperatures
do not cause microstructural changes. This work supports the latter theory, through dynamic vapor sorption
experiments on cement paste at 20–80◦C. Samples were pre-conditioned at 60% relative humidity and 20◦C,
and isotherms were measured for several humidity ranges and testing rates. The results, corroborated by
classical DFT simulations, indicate that adsorption is near-equilibrium and mostly unaffected by temperature,
whereas desorption is out-of-equilibrium due to the ink-bottle effect at high humidity, and interlayer water
at low humidity. Starting from the second cycle, desorption at higher temperatures features a shift of the
cavitation pressure and overall a smaller hysteresis. A conceptual model of pore-specific temperature-dependent
hysteresis is proposed to qualitatively explain the results.
significantly affected by moderately high temperature, 40–80◦C, typically through microstructural changes.
However literature data suggest that adsorption, not desorption, is near-equilibrium and moderate temperatures
do not cause microstructural changes. This work supports the latter theory, through dynamic vapor sorption
experiments on cement paste at 20–80◦C. Samples were pre-conditioned at 60% relative humidity and 20◦C,
and isotherms were measured for several humidity ranges and testing rates. The results, corroborated by
classical DFT simulations, indicate that adsorption is near-equilibrium and mostly unaffected by temperature,
whereas desorption is out-of-equilibrium due to the ink-bottle effect at high humidity, and interlayer water
at low humidity. Starting from the second cycle, desorption at higher temperatures features a shift of the
cavitation pressure and overall a smaller hysteresis. A conceptual model of pore-specific temperature-dependent
hysteresis is proposed to qualitatively explain the results.
Date Issued
2023-03
Date Acceptance
2022-12-21
Citation
Cement and Concrete Research, 2023, 165, pp.1-12
ISSN
0008-8846
Publisher
Elsevier BV
Start Page
1
End Page
12
Journal / Book Title
Cement and Concrete Research
Volume
165
Copyright Statement
© 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
License URL
Identifier
https://www.sciencedirect.com/science/article/pii/S0008884622003684?via%3Dihub
Publication Status
Published
Article Number
107076
Date Publish Online
2022-12-27