Examining the barrier performance of GCLs to CaCl₂ solutions in terms of bentonite mass per unit area

Bentonite is a critical component of geosynthetic clay liners (GCLs) because of its low hydraulic conductivity. However, bentonite can migrate within the GCL roll while transporting and installing the GCL. Thus, the bentonite mass per unit area (MPUA) in GCLs generally varies within the roll. Although information regarding the influence of MPUA on the hydraulic conductivity of GCLs to water is sufficient, the barrier performance of GCLs against leachates is limited. This study investigates the barrier performance of sodium (Na)-GCL under various MPUA conditions and different calcium chloride (CaCl₂) solutions. Na-GCL with MPUAs of 3.0, 4.0, and 5.0 kg/m² (M_b3, M_b4, and M_b5) were subjected to hydraulic conductivity tests with deionised water (DIW) and a calcium chloride solution. The effect of MPUA on the hydraulic conductivity of GCLs was negligible when DIW was used and was significant when the permeant was a calcium chloride solution. The hydraulic conductivity of M_b3 was above 1.0 × 10⁻⁹ m/s at all concentrations. In contrast, the hydraulic conductivity of M_b4 and M_b5 increased gradually when the permeant was 15 and 30 mM calcium chloride. Chemical analyses showed that when the cation exchange was complete, the bundle of fibres available on the GCLs controlled the hydraulic conductivity.