Water sorption isotherms and hysteresis of cement paste at moderately high temperature, up to 80 °C

Wang, Jiayi, Yio, Marcus H.N., Zhou, Tingtao, Wong, Hong S., Davie, Colin T. and Masoero, Enrico 2023. Water sorption isotherms and hysteresis of cement paste at moderately high temperature, up to 80 °C. Cement and Concrete Research 165 , 107076. 10.1016/j.cemconres.2022.107076

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Abstract

The constitutive models of concrete often consider water desorption isotherms to be near-equilibrium and significantly affected by moderately high temperature, 40–80, 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. Samples were pre-conditioned at 60% relative humidity and 20, 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.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Engineering
Publisher:	Elsevier
ISSN:	0008-8846
Funders:	Engineering and Physical Sciences Research Council
Date of First Compliant Deposit:	20 January 2023
Date of Acceptance:	21 December 2022
Last Modified:	14 Jun 2023 18:54
URI:	https://orca.cardiff.ac.uk/id/eprint/155345

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