ANALYSIS OF LAYERED TOBERMORITE STRUCTURE BY IN-SITU SMALL-ANGLE NEUTRON SCATTERING DURING WATER VAPOR ADSORPTION MEASUREMENT

Simultaneous small-angle neutron scattering（SANS）and water vapor adsorption measurements with heavy water（D2O）were performed on 1.1nm tobermorite（5CaO・6SiO2・5H2O）, a calcium silicate hydrate, to clarify the location and behavior of water molecules during adsorption measurement. Tobermorite crystal h...

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Bibliographic Details
Published inCement Science and Concrete Technology Vol. 78; no. 1; pp. 10 - 17
Main Authors TAKAGI, Natsuko, MATSUI, Kunio, KURASHIGE, Isao, TAKATA, Shin-ichi
Format Journal Article
LanguageEnglish
Japanese
Published Japan Cement Association 31.03.2025
Subjects
Heavy water
Interlayer water
Small-angle neutron scattering
Tobermorite
Water vapor adsorption
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Summary:Simultaneous small-angle neutron scattering（SANS）and water vapor adsorption measurements with heavy water（D2O）were performed on 1.1nm tobermorite（5CaO・6SiO2・5H2O）, a calcium silicate hydrate, to clarify the location and behavior of water molecules during adsorption measurement. Tobermorite crystal has a stacking structure consisting of CaO-SiO2 layers connected by SiO4 pillars in the c-axis direction, with interlayer spaces containing water molecules under room temperature and humidity. In the initial stage of adsorption at very low relative pressure range, the diffraction peaks corresponding to the stacking direction of tobermorite disappeared as D2O adsorption progressed, directly indicating the penetration of D2O molecules into the interlayer spaces. This means a matching contrast of scattering length density between the CaO-SiO2 layers and the D2O molecules intruded into the interlayer spaces, i.e., indicating D2O molecules intruding between the CaO-SiO2 layers of tobermorite in adsorption measurements. The significant increase in adsorption at low relative pressure（p/p0～0.0079）also should be due to the penetration of water molecules into the interlayer, and the amount of interlayer water molecules was estimated from the decreasing behavior of（002）peak intensity. This method can be applied to other calcium silicate hydrates, such as cement hydrates（C-S-H）, for dynamic and simultaneous observation of the water molecule conditions affecting various physical properties.
ISSN:0916-3182
2187-3313
DOI:10.14250/cement.78.10