Hydraulic conductivity and swelling of Nonprehydrated GCLs permeated with single-species salt solutions

The influence of single-species salt solutions of various concentration, cation valence, and pH on swelling and hydraulic conductivity of nonprehydrated GCLs was examined. At similar concentration, swell was largest with NaCl, KCl, and LiCl solutions (monovalent cations Na⁺, K⁺, and Li⁺) and smallest with LaCl₃ solutions (trivalent cation La³⁺). Intermediate swell volumes were obtained with divalent solutions (CaCl₂, MgCl₂, ZnCl₂, and CuCl₂). Analogous results were obtained from hydraulic conductivity tests. GCL specimens permeated with solutions containing divalent or trivalent cations had higher hydraulic conductivity than GCLs permeated with monovalent solutions or deionized water, unless the divalent or trivalent solutions were very dilute (≤0.01 M). Hydraulic conductivity increased as the concentration increased, and at high concentration (1 M) only small differences existed between hydraulic conductivities measured with all solutions. Swelling and hydraulic conductivity were related to size of the hydrated cation for monovalent cations, but no relationship was observed for different species of divalent and trivalent cations provided that the valence was the same. However, pH only influenced swelling and hydraulic conductivity when the pH was very low (<3) or very high (>12).