Relationship of Swelling and Swelling Pressure on Silica−Water Interactions in Montmorillonite

In this work, we have used the previously designed controlled uniaxial swelling (CUS) cell to obtain predetermined extents of swelling in montmorillonite. Using the CUS cell, a simultaneous measurement of swelling pressure is done with controlled swelling. 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. In addition, orientation-dependent microattenuated total reflectance (micro-ATR) spectroscopic investigations are also conducted on the controlled swelled samples. Significant changes in the silicate (Si−O) stretching region (1150−950 cm-1) have been observed with changes in swelling and orientation. The band at 1005 cm-1 (attributed in the literature to 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 vi...