Influence of swelling on the microstructure of expansive clays

The focus of this work is to elucidate the changes in microstructure during swelling in expansive clays. A new device to enable controlled swelling of clay samples was designed and fabricated. This controlled uniaxial swelling device when integrated with a closed loop mechanical testing load frame allowed for the measurement of swelling pressure at a controlled and predetermined extent of swelling of the expansive clay samples. Further, this cell offered ease of removal of samples for microanalytical testing in a scanning electron microscope. Microstructural analysis was performed on the bentonite samples after the saturated samples were allowed to swell 0, 50, and 75% beyond their original volume. The void and particle gray scales were identified in the images using energy-dispersive X-ray analysis. Digital analysis of the images using custom-developed macros and Scion Image(TM) software shows that the increase in swelling and reduction of swelling pressure due to swelling in the clay samples result in appreciable reduction in particle size. Thus, the swelling results in a breakdown of the clay agglomerates into smaller sized particles. These effects of swelling on microstructure of swelling clays could have a significant impact on stress deformation and the hydraulic properties of the clay.