Clay Water Interactions in Swelling Clays

Dr. Kalpana S. Katti

Dr. Dinesh R. Katti

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Dr. Kalpana S. Katti

Dr. Dinesh R. Katti

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June 2005
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Fall 2002
(6 MB)

PRINCIPAL INVESTIGATORS

Dr. Dinesh R. Katti

Dr. Kalpana S. Katti

Department of Civil Engineering
North Dakota State University, Fargo, ND, USA

RESEARCH OBJECTIVE:

To understand and model the interactions between water molecules and swelling clays to predict the evolution of microstructure and properties of swelling clays. This fundamental research involves developing an understanding of the physics of interactions and using and developing computational chemistry and computational mechanics techniques to bridge length and time scales from molecular to macro. The goal of this research is to develop a thorough understanding of the clay water system to better control properties geotechnical and geoenvironmental engineering and also to systematically expand use of clays in nanocomposite systems and other applications.

Evolution of Swelling Clay Microstructure During Swelling

A controlled uniaxial swelling cell (CUS) was was designed and fabricated to relate swelling, swelling pressure and the microstructure. Through our experiments, we have shown that clay particle size reduces during swelling as a result of breakdown. Relation between swelling-swelling pressure-particle size is shown.

CUS Cell

Katti, D.R., Schmidt, S., Ghosh, P., and Katti, K.S., (2005), Modeling Response of Pyrophyllite Clay Interlayer to Applied Stress Using Steered Molecular Dynamics, Clays and Clay Minerals, v52,n2, 171-178.

Clay-Water Molecular Interactions in the Interlayer of
Na-Montmorillonite Subject to External Stress

pSteered Molecular Dynamics has been used for the first time to evaluate clay water interactions

pCHARMm Force Field parameters have been developed for Na-Montmorillonite

pStress-deformation response of clay unit, clay interlayer, and water have been determined

pThe mechanism controlling deformation in montmorillonite interlayer is now better understood

pDensity of interlayer water has been evaluated with increasing stress and increasing number of water layers

FT-IR Micro ATR spectra from Si-O region of the spectrum (see paper for details)

(Nelson and Miller, 1992)

Extent of Swelling Clay Deposits in the United States

(Bordchardt, 1989)

Swelling Clay Deposits Around the World

Applications:

Geotechnical Engineering - Distress caused to engineering infrastructure is of the order of 7 to 8 billion dollars annually
Environmental Engineering - Better design and predictability of long term performance of clay barrier systems.
Clay Based Nanocomposite Systems
Pharmaceutical and Biomedical Industry

Katti, D.R., and Shanmugasundaram, V., (2001), Effect of Controlled Swelling on the Microstructure of Saturated Expansive Soil, Canadian Geotechnical Journal, 38, pp 175-182.

Steered Molecular Dynamics Modeling and Simulation of Pyrophyllite Clay Interlayer to Evaluate Mechanical Response

An atomic model for interlayer of pyrophyllite clay has been constructed. CHARMm force field parameters for pyrophyllite clay have been developed. Steered molecular dynamics simulations on dry pyrophyllite clay interlayer were conducted to quantitatively evaluate the stress deformation response of the interlayer. Our results indicate that under applied compressive stress of 0 to 1.65 GPa, the stress deformation response of the interlayer is almost linear. The predominant deformation of the clay model results from deformation of interlayer spacing. Compressive response of individual components, the clay layers and interlayer are found. The modulus of the interlayer and the clay layer is found. In this work, the steered molecular dynamics is shown to be a powerful tool to evaluate quantitative mechanical response of clay interlayers.

Two water layers in the interlayer collapsed into one under a high external stress on clay surfaces.

Interlayer spacing versus applied stress for sodium montmorillonite with three monolayers of water in the interlayer.

Schmidt, S., Katti, D., Ghosh, P., and
Katti, K. (2005). Evolution of Mechanical Response of Sodium Montmorillonite Interlayer with Increasing Hydration by Molecular Dynamics, Langmuir, 21, 8069-8076.

RELATIONSHIP OF SWELLING AND SWELLING PRESSURE ON SILICA-WATER INTERACTIONS IN MONTMORILLONITE

Undisturbed clay samples at well defined swelling (0%-75%) were removed from the CUS cell and analyzed using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. Orientation dependant micro-attenuated total reflectance (ATR) spectroscopic investigations are also conducted on the controlled swelled samples. Significant changes in the silicate (Si-O) stretching region have been observed with changes in swelling and orientation. The band arising from Si-O vibrations when montmorillonite platelets are normal to incident radiation) is most pronounced for the 0% swelled sample and diminishes with swelling. The band associated with perpendicular vibration increases with swelling. Thus intensity of this band increases with misorientation of clay particles. Our results indicate that the reduced particle size as ascertained from SEM cryoimaging, with increased swelling is related to increased misorientation of the clay platelets. At 0% swelling, the clay platelets are most oriented and have largest particle size. The rearrangement of clay platelets as seen in the orientation dependant spectra are a direct result of the breakdown of the clay particles with increased hydration resulting from increased swelling.

Katti, K.S., and Katti, D.R., (2006), Relationship of Swelling and Swelling Pressure on Silica-Water Interactions in Montmorillonite, Langmuir, in-press.

Coming soon : Results of Discrete Element Modeling