Hydraulic conductivity of a dense prehydrated GCL permeated with aggressive inorganic solutions Available to Purchase

A series of swell and hydraulic conductivity tests were conducted with aggressive aqueous solutions (1 M CaCl₂, 1 M NaCl, HCl solution with pH 1.2, and NaOH solution with pH 13.1) and deionised water (DI) on two GCLs. One GCL is moistened with an aqueous solution and calendered during manufacturing to form a dense prehydrated (DPH) GCL having a mass of dry bentonite per area (M_A) of 6.0 kg/m². The other is a conventional GCL containing air-dried granular bentonite with M_A = 4.3 kg/m². The montmorillonite fraction of the bentonite is similar in both GCLs (81% conventional, 89% DPH). Comparable free swell was obtained with both bentonites in the NaCl, CaCl₂ and acidic (HCl) solutions. However, with the basic (NaOH) solution, free swell of bentonite from the DPH GCL was 90% larger than that from the conventional GCL. The hydraulic conductivity tests were conducted for approximately 300 days. The DPH GCL had much lower hydraulic conductivity to all permeant liquids than the conventional GCL. For example, the hydraulic conductivity of the DPH GCL to 1 M CaCl₂ is 3.7 × 10⁻¹² m/s, whereas it is 9.1 × 10⁻⁷ m/s for the conventional GCL. The hydraulic conductivity of the DPH GCL to DI water is also three times lower than that of the conventional GCL (4.1 × 10⁻¹² compared with 1 × 10⁻¹¹ m/s).