Amended bentonites have been proposed with the primary purpose of improving their chemical compatibility relative to conventional bentonite. As these materials are relatively new, their durability and long-term performance need to be evaluated. Wet-dry conditions may occur in many applications where bentonite liners are in use. In this study, two amended materials, the MultiSwellable bentonite and a DPH (Dense Prehydrated) GCL were subjected to simulated wet-dry ageing. Distilled water (DW) and natural seawater (NSW) were used as permeant liquids. After five wet-dry cycles, the hydraulic conductivity of both materials increased by two to three orders of magnitude. Unhealed desiccation cracks were identified as responsible for the increase in permeability. Conversely, wet-dry ageing in DW did not impact significantly the permeability of the DPH GCL. For both materials, post-test swell index and XRD diffraction indicated a loss of the chemical amendment, likely solubilised and/or eluted during the wet phases. The results point out that further investigation is necessary to fully address the permanence of swelling and permeability performances of these amended clays after long-term field service. Adequate measures are recommended to prevent or limit desiccation damage for use in applications where aggressive inorganic permeant liquids (e.g., NSW) are present. |
