Bitumen is a natural product – like clay – and its use for waterproofing dates to ancient times. Bitumen was primarily used for waterproofing irrigation canals in Mesopotamia, 4,000 years BC. Sections of these waterproofed canals are still in existence today. A bituminous geomembrane (BGM) is manufactured by impregnating a polyester geotextile with an elastomeric bitumen compound. The geotextile provides a high mechanical resistance and a high puncture resistance. The bitumen provides the waterproofing properties and ensures longevity of the framework by protecting the geotextile. The durability of a BGM is measured in terms of how its key components, namely the polyester geotextile and the bitumen, maintain their mechanical properties and low permeability over time under its operating conditions, either remaining exposed to UV radiation and weathering or covered with soil, subject to biodegradation by bacteria.
The paper presents information regarding the durability of BGM and it addresses the specific characteristics that justify its longevity, including its low thermal expansion coefficient (leading to zero stress-cracking and therefore no phenomenon of fatigue) and its quick relaxation over time demonstrated by laboratory CEBTP of the French Ministry of Transport. Results of field-testing naturally aged BGM under covered conditions after 15 and 35 years of service at an ICOLD dam in Corsica (France) are presented. Life expectancy studies were carried out by the French company ANDRA for the use of BGM for the containment of low and medium intensity nuclear wastes. These studies concluded, after seven years of testing, that biodegradation of BGM in confined conditions is longer than 300 years. And finally, the results of BGM testing in North America done by the Department of Nuclear Energy in the Brookhaven National Laboratory (Upton, NY) and the Batelle Pacific Northwest Laboratory (Richland, WA) validates a life expectancy of BGM of 300 and even 1,000 years in confined conditions.
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