INFLUENCE OF PORE FLUID COMPOSITION ON VOLUME OF SEDIMENTS IN KAOLINITE SUSPENSIONS

Reported in this paper is a study of the influence of pore fluid compo sition on sediment volume of kaolinite suspensions. Laboratory tests h ave been conducted with kaolinite in water with NaCl, CaCl2 and AlCl3 of different concentrations and in 10 types of organic liquids of vary ing values of static dielectric constant. The types of tests performed include regular suspension tests and leaching and cyclic leaching tes ts on kaolinite sediments. In the leaching tests, sediments formed dur ing the regular suspension tests in water of low salt concentration we re subsequently leached with water of high salt concentration. In the cyclic leaching tests, the salt concentration was increased and then d ecreased. The purpose of the leaching and cyclic leaching tests was to study the change in existing equilibrium fabric caused by subsequent changes in the concentration of salt in pore fluid. Results of the sus pension rests indicate that sediment volume of a water suspension decr eases with increase in ion concentration and increase in valence of ca tion. Leaching and cyclic leaching tests indicate that substantial cha nge in salt concentration is required to change the existing fabric. T he effect of dielectric constant of pore fluid on sediment volume is s omewhat complex. As the dielectric constant increases from 1.9 for hep tane to 110 for formamide, sediment volume first decreases, assuming a minimum at 24 for ethanol, increases with a maximum at 80 for water, and decreases again until 110 for formamide. An approximate physico-ch emical analysis model is used to interpret some of the data in a quant itative manner. In the analysis model, recently developed theories of double-layer repulsive and van der Waals attractive forces are combine d to simulate the behavior of suspensions.