On the influence of ionic strength on the rheological properties of kaolin

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Examensarbete för masterexamen
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2019
Författare
Serrano Romero, Julio Cesar
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This Thesis presents an experimental study that investigates the effect water content and pore water chemistry on the emerging hydro-mechanical response of clay samples. In order to capture the basic strength and stiffness response as function of strain amplitude and rate, rheology experiments have been performed. As opposed to standard geotechnical tests rheology experiments are fast to execute, more consistent and only require small sample volumes. In order to properly benchmark the rheometer apparatus for testing soft soils kaolin was used. The latter reduces the complexity associated with natural materials at the expense of some saillant features (such as the high sensitivity in sensitive clays) and allows to control the initial conditions to the required degree. The samples consisted of kaolin slurries prepared at differnt void ratios and with different initial pore water salinities, one slurry with a water content equal to the liquid limit and another slurry with 1.5 times the liquid limit. Furthermore, a reconstituted sample was consolidated to 80 kPa. Two series of slurries were prepared, i.e. a reference slurry with distilled water and saline slurry where 0.2 M NaCl was added to the pore water. The results showed that the effect of NaCl is most pronounced for the slurries with water content equal to the liquid limit and 150% the liquid limit. In contrast the effect of NaCl in the reconstituted consolidated sample was less evident. Finally, a different series was performed that emulated leaching of the saline pore water composition to simulate some of the processes that occur during the formation of sensitive clay deposits. These initial tests show that the beneficial effects of a saline injection can be fully reversed by subsequent leaching with fresh water.
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Ämne/nyckelord
kaolinite, reconstituted sample, slurry, ionic influence, NaCl, viscosity, leaching, quick clay, double layer, pH
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