Ammonium Ion-Exchange and Plasticity of Kaolinitic Kentucky-Tennessee Clay

Abstract

The plasticity of kaolinitic Kentucky-Tennessee clay (KT), before and after an ion-exchange with 1N-CH₃COONH₄ solution was studied by a uniaxial compression test. Kaolinitic clay of the weathering-origin clay showed a large amount of dissolution of Ca²⁺ and Mg²⁺ ions after the ion-exchange, while kaolinitic clay of the hydrothermal origin kaolinitic clay showed a very small amount of divalent cations dissolved. Large amount of divalent cations predominantly dissolved from the montmorillonite contained in the weathering-origin clays and partly from the surface of kaolinitic clay particle. The zeta potential of the Kentucky-Tennessee clays showed a large negative charge with increasing the pH after the ion-exchange. According to an analysis of uniaxial compression test performed on green bodies, the plasticity of Kentucky-Tennessee clays degraded extensively after the ion-exchange. A clear relationship between the plasticity of kaolinitic clay and the zeta potential was found.