Electrokinetic stabilization of kaolinite by injection of Al and PO43− ions

Abstract

Stabilization of a kaolinite bed by the electrochemical injection of aluminium and phosphate ions has been investigated. Electrical gradients of 2 V/cm or less constituted the predominant driving force for ion transport under a 433 µA/cm2 constant direct current density. The changes in the kaolinite properties and pore fluid characteristics due to electrokinetic treatment were analysed. Average increases in undrained shear strength of 500–600% were observed for phosphoric acid and aluminium sulfate/phosphoric acid treatments of the kaolinite. Electrokinetic processing caused an average increase of 30% in the Atterberg limits. It is hypothesized that injection of phosphate and aluminium ions into the kaolinite specimens modified the pore fluid, leading to an increase in shear strength by ion exchange and precipitation mechanisms. However, the strength increase observed was not homogeneous throughout the specimen.