Sedimentation Behavior of Fly Ash-Kaolinite Mixtures

The sedimentation behavior of fine grained soil is largely dependent on its pore fluid chemistry. Different ionic concentration will lead to different fabrics of soil suspension, such as dispersion, aggregation, and flocculation. The ionic concentration also influences the thickness of the Diffuse Double Layer (DDL), which leads to the change in the final sediment volumes. Besides the ionic concentration influence, adding different amount of fly ash (FA) can also cause different sedimentation behaviors. The objective of this research was to quantify the interaction between fly ash and fine grained soils by comparing the influence of ionic concentration with that of fly ash on the sedimentation behavior of kaolinite. It was found that an increase in the percentage of fly ash in FA-kaolinite mixture could cause an increase in the settling speed. The final sedimentation volume decreased as the ionic concentration increased. The addition of fly ash was found more efficiency than the ionic concentration, because the fly ash could not only interact with kaolinite particles but also increase the ionic concentration in the dissolution by precipitation of Calcium hydroxide and pozzolanic reaction products.