Influence of freeze-thaw cycles on clay structures

Laboratory and field scale freezing experiments were performed in order to clarify the structural changes of the clay fabric. The main parameters for the different types of ice formation (ice lenses, ice layers, ice cracks, bundles of ice plates) in the frozen zone are the mineralogical composition of the investigated clays, the type of cations adsorbed on clay external and interlayer surface and the composition of the pore solution. The freezing process rearranges clay particles, forms aggregates and macropores and thus leads to an aggregate-porous state different from the original structure. This aggregated state is preserved in a series of natural clays with low swelling properties, but is destroyed in an industrial high swelling clay during melting. The fabric change is also influenced by the ion transport from the unfrozen to the frozen zone leading to a different electrolyte content in pore water and therefore to a different flocculation behaviour.