Ageing resistance of HDPE-geomembranes – Evaluation of long-term behavior under consideration of project experiences

A question frequently asked about HDPEgeomembranes is “how long will they last?” After more than 30 years of experience with exposed (weathered) HDPE-geomembranes, the authors address the question from the designer’s view point. The engineer needs to know, if available test methods tell us how long the geomembrane will last, and which properties must be specified and what are the minimum acceptable values?” The main focus of this paper is the practical approach for evaluation of the durability of exposed (weathered) HDPE-geomembranes. HDPE-geomembranes used in four projects after exposure in different climatic zones were tested for the amount of stabilization and for changes of their properties. After up to 30 years exposure to weathering these HDPE-geomembranes reveal a reduction of the antioxidant content, whereas the mechanical properties did not significantly change. The test results presented in this paper indicate clearly that the lining systems still work in their desired function and remaining antioxidants remain capability to provide further protection against degradation even after this time. On the basis of this research the appropriate properties required to evaluate the durability of HDPE-geomembrane lining systems are identified.