Zeta potential of cation-treated soils and its implication on unfrozen water mobility
Margaret M. Darrow, Rui Guo, Thomas P. Trainor
Abstract
Most frozen soils contain unfrozen water – water that remains liquid at subfreezing temperatures – which affects a frozen soil's strength and contributes to frost heave. Among the variables that influence the flow of unfrozen water through a freezing soil is the presence of clay minerals and their adsorbed cations. Zeta potential (ζp) is one measure of clay mineral surface properties that may provide insight into the interaction of mineral surfaces with unfrozen water films; however, one gap in the literature is the lack of ζp measurements at subfreezing temperatures. The purpose of this research was to measure the ζp of six cation-treated soils as a function of temperature, including measurements at a subfreezing temperature. The results indicate that the magnitude of the ζp decreases as a function of temperature. The ζp of the divalent cation-treated clays generally had a smaller magnitude and was less sensitive to temperature than the monovalent cation treatments, suggesting that unfrozen water mobility (and thus frost heave) may be correlated with smaller ζp. Based on these results, it is hypothesized that the amounts of immobile unfrozen water may depend on the ζp at the shear plane. To complement the results of this research, we recommend additional tests to determine the viscosity of unfrozen water as a function of temperature.