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 swellin g device when integrated with a closed loop mechanical testing load frame a llowed for the measurement of swelling pressure at a controlled and predete rmined extent of swelling of the expansive clay samples. Further, this cell offered ease of removal of samples for microanalytical testing in a scanni ng electron microscope. Microstructural analysis was performed on the bento nite samples after the saturated samples were allowed to swell 0, 50, and 7 5% beyond their original volume. The void and particle gray scales were ide ntified in the images using energy-dispersive X-ray analysis. Digital analy sis of the images using custom-developed macros and Scion Image(TM) softwar e shows that the increase in swelling and reduction of swelling pressure du e to swelling in the clay samples result in appreciable reduction in partic le 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.