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Die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH) Influence of clay mineral composition on complex permittivity of clays.

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Präsentation zum Thema: "Die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH) Influence of clay mineral composition on complex permittivity of clays."—  Präsentation transkript:

1 Die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH) Influence of clay mineral composition on complex permittivity of clays and soils Heike Kaden Competence Center for Material Moisture (CMM), Karlsruhe Institute of Technology

2 Die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH) Agenda Motivation and objectives Permittivity – theory Samples and excursus of clay mineralogy Summary and outlook 2

3 Die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH) material permittivity vacuum1 air dry soil3-6 dry clay4 dry sand4-6 wet soil29 wet clay (non-swellable)27 swellable clays100 – 250* wet sands15-25 water81 bound water Motivation and objectives 3 Permittivity (ε) in high MHz range (G EOPHYSICAL S URVEY S YSTEMS I NC.,2001) (C HEN & O R 2006) * Low MHz range (R AYHATNA & S EN, 1986) w = f(ε r )

4 Die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH) Permittivity of clays and soils 4 Permittivity FrequencyTemperatureDensity Water content Porosity Electrical conductivity Specific surface area Mineral composition X-ray diffractometry (XRD) X-ray fluorescence analysis (XRF) Simultaneous thermal analysis (STA) Cation exchange capacity (CEC)

5 Die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH) Permittivity – theory Complex permittivity ε* transmissibility of materials for electrical fields, complex number ε* = ε + jε Relative permittivity ε r polarizability of materials, dimensionless ε r = ε* / ε 0 Polarization mechanisms interfacial polarization orientation polarization ionic polarization electronic polarization (displacement polarization) 5 increasing frequency

6 Die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH) Permittivity – theory 6 ε r = real part of relative permittivity (dispersion) ε r = imaginary part of relative permittivity (absorption), dielectric loss Relative permittivity of water (A GILENT T ECHNOLOGIES,2009) working range

7 Die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH) Permittivity of multi-phase-mixtures 7 α = geometry factor Roth et al. 1990: α = 0.46 ε : permittivity v: volumetric weight bulk watersoil air mixing rules

8 Die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH) Samples and excursus clay mineralogy 8 clay minerals 1:1 layer silicates2:1 layer silicates J ASMUND & L AGALY (1993) swellablenon-swellable smectites vermiculites talc-pyrophyllite group illites micas chlorites kaolinite serpentine

9 Die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH) Smectites 9 Al III oxygen hydroxyl groups water Si IV M + x+y (H 2 O) n (Al 3+, Fe 3+ 2-y Mg 2+, Fe 2+ y ) (Si 4-x Al x )O 10 (OH) 2 montmorillonite, beidellite, nontronite Al III for Si IV Mg II for Al III Fe II /Fe III for Mg II ; Al III E MMERICH et al. (2009) and W OLTERS et al. (2009)

10 Die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH) Interaction of smectites and water 10 J ASMUND & L AGALY (1993) increasing relative humidity high cation exchange capacity meq/100 g high water binding capacity water adsorption on inner surface and outer surface high specific surface area up to 750 m²/g

11 Die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH) Cation Exchange Capacity (CEC) 11 sampleCEC [meq/100g] bentonite (EXM1912)120 bentonite (Volclay)84 bentonite (Calcigel)63 illite (Arginotech GI)25 ceramic kaoline (FW830)4 limestone3 finesand (N45)2 silty quartz-feldspar-mixture (FS700)2

12 Die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH) Grain size of clays and soils 12 sand silt clay

13 Die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH) Summary and outlook Dielectric properties of soils can be used for volumetric water content measurements. Permittivity of bound water ( ) is lower than permittivity of free water ( 81), which can lead to underestimation of water content in highly swellable clays as they adsorb large amounts of water. There are still phenomena to be explained: permittivity values of up to 250 in bentonite-water-mixtures Determination of moisture in soils with high amount of swellable clays requires special calibration of moisture-permittivity-relationship.. 13

14 Die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH) Thank you for your attention! 14

15 Die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH) Literature Chen, Y. and Or, D., 2006: Geometrical factors and interfacial processes affecting complex dielectric permittivity of partially saturated porous media. Water Resources Research, 42: 1-9. Emmerich, K., Wolters, F., Kahr, G., and Lagaly, G., 2009: Clay profiling: The classification of montmorillonites. Clays and Clay Minerals, 57: Jasmund, K. & Lagaly, G., 1993: Tonminerale und Tone. Steinkopff Verlag Darmstadt. 490 pp. Klein, K. and Wang, Y.-H., 2005: Towards a Better Understanding of the Electro-Magnetic Properties of Soils, IUTAM Symposium on Physicochemical and Electromechanical Interactions in Porous Media, Raythatha, R. and Sen, P. N., 1986: Dielectric properties of clay suspensions in MHz to GHz range. Journal of Colloid and Interface Science, 109: Roth, K., Schulin, R., Flühler, H., and Attinger, W., 1990: Calibration of Time Domain Reflectometry for Water Content Measurement Using a Composite Dielectric Approach. Water Resources Research, 26: Wolters, F., Lagaly, G., Kahr, G., Nueesch, R., and Emmerich, K., 2009: A comprehensive characterization of dioctahedral smectites. Clays and Clay Minerals, 57:


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