properties (e.g., Rowe and Abdelatty 2012, Bradshaw et al. 2013, Bradshaw and Benson 2014). However, temporal development of the cation exchange processes has not been widely investigated. Therefore, a comprehensive investigation was conducted to systematically analyze the cation exchange characteristics of a GCL as a function of time, concentration of hydration liquid, temperature and applied stress. Results of the time-dependent analysis conducted at 20°C (68°F) with hydration liquids of variable concentrations under no stress conditions is presented herein. Experimental Test Program Materials Experimental analysis was conducted on a conventional medium-weight needlepunched nonwoven-nonwoven GCL with granular bentonite that is commonly used in the U.S. (CETCO Bentomat DN). Figure 3 presents the granular sodium bentonite that was removed from the sample roll used for testing in the study. The minimum bentonite dry mass per FIGURE 2 (TOP) Effects of dilute and aggressive permeant solutions on liquid transport through sodium bentonite (from Tian et al. 2019) FIGURE 3 (BOTTOM) Granular bentonite extracted from GCL GeosyntheticsMagazine.com 13http://www.GeosyntheticsMagazine.com