The Chemical Durability of Elastomeric Bituminous Geomembranes (BGMS) in Different Geoenvironmental Applications at Elevated Temperatures

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Authors
Samea, Alireza
Keyword
Geosynthetics , durability , bituminous geomembrane , heap leach pads , time to nominal failure , service-life , Thermo-oxidative degradation , brittle rupture
Abstract
The chemical durability of elastomeric bituminous geomembranes (BGMs) is investigated using laboratory accelerated immersion tests for different geoenvironmental applications. The effects of elevated temperatures, thickness, and incubation media on the mechanical, rheological, and chemical properties of BGMs are examined. Exposure to elevated temperatures resulted in the thermo-oxidative degradation of the bituminous coat that increased its rigidity. Concurrently, the BGM exhibited degradation in the reinforcement layer resulting in the loss of its mechanical properties. The rate of degradation in the BGM components is shown to be different and dependent on the incubation media. In air, the BGM exhibited thermo-oxidative degradation in the bitumen coat, leading to its brittleness before any degradation in the mechanical strengths. In contrast, exposure to water resulted in fast degradation of the mechanical properties, while the bitumen coat exhibited substantially less degradation than in air. Immersing a 4.8 mm thick BGM in pH 0.5, 9.5, and 11.5 synthetic mining solutions shows that the degradation rates of all properties are faster in high pHs than in pH 0.5. Additionally, the degradation of this BGM is compared to a 4.1 mm thick BGM produced by the same manufacturer when immersed in synthetic municipal solid waste (MSW) leachate. It is shown that the 4.1 mm has slightly faster degradation in its chemical, mechanical, and rheological properties than the 4.8 mm BGM. Relative to the mining solutions, the degradation in the bitumen coat was slower in the MSW leachate, while the degradation in the reinforcement layer was much faster. The time to nominal failure (tNF) of the BGM is predicted in air, water, mining solutions, and MSW leachate at field temperatures using Arrhenius modelling. Using a custom-designed apparatus to age the BGM under single-sided exposure, it is shown that degradation times are substantially longer in single-sided than in double-sided immersion experiments only for the mechanical properties. However, the bitumen coat degradation is not affected by the ageing method. Additionally, factors established from the relative degradation in the double-sided and single-sided experiments were used to shift the predictions of the tNF at field temperatures to the single-sided field exposure condition.
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