Detailed studies of drying and crack formation in aggregated colloidal suspensions

In this thesis we present evidence that particle interaction forces play an important role in the cumulative drying behavior of suspensions of aggregated colloidal particles. In particular, they control the shape and deformation behavior during drying of these suspensions. We identify a single dimensionless group Q¯ that can be used to predict drying behavior. We use a two-phase fluid model with the compressive yield stress constitutive equation to describe consolidation behavior in these systems. In the falling rate period we propose a simple diffusion mechanism that describes drying rate behavior during this period of drying. We describe the drying front that forms when the gas-liquid interface moves inside the porous bed by a single position of constant concentration. By combining the two-phase fluid model with the compressive yield stress constitutive equation and the diffusion model of drying in the falling rate period we characterize the development and evolution of stress in these aggregated systems as a function of moisture content. The volume fraction at which cracks begin has been identified as coinciding with the changeover from consolidation to de-saturation in these systems. Additionally we show that by adjusting the initial volume fraction of our suspensions, we can significantly alter their elastic properties so that the corresponding strain that these suspensions experience during drying can be significantly reduced.