Cavitation of water in hardened cement paste under short-term desorption measurements
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Water vapor sorption isotherm measurement is one of the promising techniques to understand the microstructure of hardened cement paste, because it always gives a higher surface area than sorption isotherm measurements performed with other adsorbents such as nitrogen and argon, which implies that water molecules can probe the widest range of the microstructure of hardened cement pastes. When, at 20 °C, the water sorption measurement is conducted such as to last for a few days, a characteristic behavior—a sudden drop in adsorbed amount around a relative humidity of 0.35—is always observed on the desorption branch. Here, we prove that this sudden drop is caused by water cavitation, based on an analysis of experimental sorption isotherms acquired at various temperatures, scanning isotherms, and length-change isotherms. Cavitation in hardened cement paste is likely to occur in the C–S–H gel pores constricted by the C–S–H interlayer space.
KeywordsWater vapor sorption isotherm Cavitation
A part of this research is supported by JSPS KAKENHI grant number 18H03804. The used materials and facilities are supported by the Nuclear Regulatory Authority (NRA, Japan) and JSPS KAKENHI grant number 15H04077.
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Conflict of interest
The authors have no conflict of interest directly relevant to the content of this article.
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