Swelling behavior of Na- and Ca-montmorillonite up to 150°c by in situ x-ray diffraction experiments

Shoji Morodome, Katsuyuki Kawamura

    Research output: Contribution to journalArticlepeer-review

    85 Citations (Scopus)


    The effects of temperature on the swelling properties of smectites are important for a variety of different geological conditions, but studies on this topic have been rather limited. The purpose of this study was to investigate the swelling behavior of Na- and Ca-montmorillonite at various temperatures greater than room temperature, up to 150°C, using in situ X-ray diffraction (XRD) analysis. A sample chamber was designed, the temperature and humidity of which were controlled precisely, for environmental in situ measurements. The XRD measurements were performed at small relative humidity (RH) intervals for precise observation of the swelling behavior. The swelling behavior of Na-montmorillonite showed distinct zero-, one-, and two-layer hydration states. The basal spacings of Na-montmorillonite changed continuously with RH for various temperatures in the transition region between the zero- and one-layer hydration states, and the swelling curves of the transition region moved to greater degrees of RH with increasing temperature. The basal spacings jumped from the one- to two-layer hydration states for all temperatures at almost the same RH. Thebasal spacings of Ca-montmorillonitechangd continuously from thezro- to thetwo-layr hydration states at all temperatures. This behavior is remarkably different from that of Na-montmorillonite. At low-RH conditions, the d001 value of Ca-montmorillonite decreased with increasing temperature. The swelling curves of Ca-montmorillonite did not show a plateau at any temperature for the one-layer hydration state. The swelling curves of Ca-montmorillonite moved to greater RH with temperature, similar to the transformation region between the zero- and one-layer hydration states in Na-montmorillonite. These differences between Na- and Ca-montmorillonite are related to the hydration powers of exchangeable cations.

    Original languageEnglish
    Pages (from-to)150-160
    Number of pages11
    JournalClays and Clay Minerals
    Issue number2
    Publication statusPublished - Apr 1 2009


    • Basal Spacing
    • Hydration
    • Interlayer cation
    • Montmorillonite
    • Relative humidity
    • Smectite
    • Swelling
    • Vapor pressure
    • X-ray diffraction

    ASJC Scopus subject areas

    • Water Science and Technology
    • Soil Science
    • Geochemistry and Petrology
    • Earth and Planetary Sciences (miscellaneous)


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