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 ImageTM 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.Key words: expansive clays, swelling, swelling pressure, microstructure, image analysis, scanning electron microscopy.

This paper deals with fundamental molecular issues related to macroscopic mechanical properties of nano-meso-microscale montmorillonite clay particulate systems. Molecular interaction of high aspect montmorillonite particles with solvents has large influence on resulting swelling characteristics in clays consisting of montmorillonite. A new controlled uniaxial swelling (CUS) cell is designed which allows a simultaneous measurement of swelling and swelling pressure in addition to ease of removal of undisturbed samples for electron microscopic and fourier transform infrared spectroscopic investigations. Our work shows that the swelling behavior of montmorillonite directly results from breakdown of large particles to smaller nano and meso scale particles with increased water incorporation in the interlayers. The Si-O vibration band regions of the montmorillonite spectra obtained at controlled amounts of swelling from 0-100% (where 0% swelling is defined as fully saturated samples under no volume change) show changes in band shape, intensity, and positions resulting from increased H-bonding in the interlayers and surface of montmorillonite particles. In addition, orientation dependant micro-attenuated total reflectance (ATR) spectroscopic investigations are also conducted on the controlled swelled samples. Our results indicate that the reduced particle size with increased swelling is related to increased misorientation of the montmorillonite platelets. The relationship between molecular interactions microstructure and macroscopic response (swelling and swelling pressure) is the key to development of novel nanocomposite systems based on montmorillonite with tailored properties.

In this paper, we describe our efforts in knowledge building by creating visualizations. Our efforts include problem-based learning. We have identified a problem that the students have in learning OOP. To solve that problem we engage our students in the classroom using existing visualizations created by students of the earlier class, then we have the currents students improve the existing visualizations, or create new visualizations for future use in the same class. We describe the process of building knowledge, problem based learning, the details of the visualizations, our observations and the merits of this approach.

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ProgrammingLand is an online system for delivering content to introductory computer science courses as a substitute for a conventional textbook. Because the system has a large number of exhibits, sometimes students were not finding the material needed. The system was recently enhanced with several agents to direct students to pertinent locations. This paper discusses the capabilities and techniques of these agents.Preliminary data from the use of ProgrammingLand in two different introductory programming classes is discussed. This data suggests that the agents are successful in aiding students, especially those who are struggling.