Water content, swell index and cation exchange of GCLs due to subsoil hydration

This study investigates the final water contents and swell indices of GCLs depending on the hydration duration. In the content of this study, traditional Na-GCL and two polymer treated GCLs (PT-GCL-1 and PT-GCL-2) were hydrated over compacted zeolite subsoil. GCL hydrations were conducted in 0.15 m diameter flexible wall permeameters under 10 kPa confining pressure for 30 days and 90 days. At the end of the hydration durations, GCLs were removed from the permeameters and bentonite samples were taken from the GCLs to determine the final water contents and swell index values. Except Na-GCL, increasing the hydration duration from 30 days to 90 days caused slight reduction in the final water con-tents of PT GCLs. In contrast, the final water content of 30 days hydrated Na-GCL increased from 66% to 83% at the end of 90 days of hydration. When comparing to the traditional Na-GCL, the swell indices (SI) of PT GCLs significantly affected from the subsoil hydration with time. That is, the SI of new Na-GCL was 21 mL/2g and decreased to 18 mL/2g after 90 days of hydration. However, the SI of PT-GCL-1 dramatically decreased from 38 ml/2g to 21 ml/2g after 30 days and to 11 ml/2g after 90 days of hydra-tion. Similarly, the SI of PT-GCL-2 decreased from 29 ml/2g to 23 ml/2g after 30 days and to 9 ml/2g af-ter 90 days of hydration. The decrease in the SI values can be attributed to the cation exchange that took place between the zeolite and GCL.