When mine wastes are potentially acid generating, various management options and reclamation strategies may be used to inhibit acid production. In most of the Canadian provinces with a humid climate, oxygen barriers such as cover with capillary barrier effect (CCBE) are considered as the most viable reclamation option. In the context of sustainable development, it is strongly recommended to use natural (silt and/or sand) or recycled (from mine activities such as non-reactive tailings and waste rocks) materials available around the mine sites for their reclamation; these materials can be used as moisture retention layer (MRL) in the CCBE.
Sludge generated by the active treatment of acid mine drainage by neutralization with an alkali product (such as lime) can also be valorized, particularly in soil-sludge mixtures (SSMs). However, the long-term chemical stability of such SSMs to acid rainwater still needs to be investigated beforehand.
The objective of this paper is to assess the long-term chemical stability of glacial till-sludge mixtures (TSMs) as MRL materials. For this purpose, sludge sampled from two mine sites (A and B) located in the Abitibi region were used. Each sludge was mixed with a till material to achieve six homogenized mixtures (TSMs) at different mass ratios. Indeed, the TSMs were prepared using different wet proportions of sludge (10, 20, and 30% by wet mass of till). The physical, chemical and mineralogical properties of all the materials were then characterized. The sludge A & B, till and TSMs were used in nine column and submitted to wetting (with rainwater) and drying cycles (in total 12). The leachates were collected after each cycle for physicochemical analyses. Then, the chemical stability of the mixtures is assessed from the results, which are also discussed in terms of lifetime assessment of the till-sludge mixtures based on the carbonate dissolution potential.

Recently, the use of geosynthetic clay liners (GCL) in composite liners has extended to harsh environments like Arctic and Antarctic regions as the main purpose of using GCLs in composite liner is to minimize the advective flow of contaminant if there is any hole in the geomembrane. The two parameters controlling the effectiveness of this composite system are the hydraulic conductivity, k, of the GCL and interface transmissivity, θ, of the GMB/GCL interface. This paper reports a new laboratory test setup to simulate the field condition for applying freeze-thaw cycle on the interfaces of the GCL-GMB and also reports the results of a preliminary study of a more conventional approach to subjecting freeze-thaw cycles by putting the specimens in and out of a fridge for 5 and 16 freeze-thaw cycles, and the effect of hydrating fluid and permeant solution on interface transmissivity for a range of stresses (10 kPa, 15 kPa, 20 kPa) typical for cover applications. The new test setup allowed the hydration from the subgrade as well as the application of freeze-thaw cycles which attracted water and formed ice lens at the GMB-GCL interface and in the GCL itself due to cryosuction. The preliminary results show that the formation of ice lenses after applying freeze/thaw cycles had significant effect on the interface transmissivity at 10 kPa. On the other hand, when the GCL was prehydrated, subjected to 5 and 16 cycles of freeze-thaw and permeated with RO water and pore fluid there was no significant effect of 5 freeze/thaw cycle but there was an effect for 16-cycles freeze-thaw cycles.