Multiscale modeling of swelling clays: A computational and experimental approach

Abstract

Expansive clays such as montmorillonite cause severe distress to infrastructure due to swelling. The swelling of montmorillonite clay is also the basis for its use in many commercial applications such as drilling muds in petroleum engineering, as landfill liners in environmental engineering and in making polymer clay nanocomposites. The focus of this work is to carry out a systematic experimental and numerical study to understand and model behavior of Na-montmorillonite at molecular and particulate level to find mechanism of swelling in the Na-montmorillonite interlayer. Experimental results show breakdown of particles with an increase in swelling of the clay. This phenomenon was numerically studied by developing a modified Discrete Element Method (DEM) model that incorporates the latest developments in both clay and computer science, and can simulate particle subdivision. DEM results show the role of particle subdivision on swelling and swelling pressure. In understanding the true mechanism of swelling, it is essential to incorporate the interactions between clay molecular structure and the interlayer water molecules. For bridging the length scales, we have also evaluated the stress deformation response of the clay molecular structure using Molecular Dynamic (MD) simulations. Simulation results show that the deformation in the clay molecular structure due to external stress is mostly due to deformation of the water molecules in the clay interlayer. A new experimental technique which enables us to capture the molecular changes in the clay molecular structure upon hydration is also developed. This work provides a foundation for multiscale modeling of swelling clays.