Abstract
Polyolefin geosynthetics are susceptible to oxidative degradation, which in turn leads to diminished mechanical properties in geotechnical constructions. When using these materials, it is extremely important to determine their durability over time in particularly aggressive conditions. In order to prolong the life of a geosynthetic material, antioxidants are added during the manufacturing process. The function of antioxidants is to prevent polymer oxidation reaction in time. As the antioxidant content is depleted, the polymer becomes less protected towards oxidative attacks. This article describes the aging process of uniaxial (high density polyethylene) HDPE geogrids under the influence of chemical and environmental factors. Evaluations of accelerated aging test of the uniaxial HDPE geogrids were incubated in simulated landfill conditions for a period of 12 months. Three temperatures (25 °C, 45 °C, and 75 °C) were selected for carrying out the aging experiments in aqueous solutions mimicking landfill conditions. The changes observed by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and melt flow index (MFI) correlate with the mechanical properties of the aged geogrid. No significant changes in the FTIR and MFI were observed over the 12 months of accelerated aging tests at none of the three different temperatures. The oxidation induction time (OIT) test showed no antioxidant remaining in the geogrid following eight months of aging test at 75 °C. No significant changes in the influence of accelerated aging tests on the average relative elongation at 25 °C and 45 °C of the tested material were observed. Accelerated aging tests at 75 °C showed that the mean elongation of 12.12% for the sample not subjected to accelerated aging tests (new sample) increased to 19.32% (after 12 months of incubation).
Highlights
In the geosynthetic industry, polyolefin refers to synthetic products consisting of at least 85%by weight of polyethylene (PE) or polypropylene (PP) [1,2]
The oxidation induction time (OIT) test showed no antioxidant remaining in the geogrid following eight months of aging test at 75 ◦ C
Accelerated aging tests at 75 ◦ C showed that the mean elongation of 12.12% for the sample not subjected to accelerated aging tests increased to 19.32%
Summary
Polyolefin refers to synthetic products consisting of at least 85%by weight of polyethylene (PE) or polypropylene (PP) [1,2]. The use of polyolefin geosynthetics has been constantly increasing in different areas of civil engineering applications. HDPE (high density polyethylene) geogrids have been used as reinforcement materials in slopes, walls, foundations, and base courses for about five decades. First reinforced soil structures in the world were built in France in 1970 [3,4]. In the United States, structures of this type were built since 1974 [5] and in Poland, in engineering practice, they are used for about 30 years [6]. HDPE geogrids have found wide applications in the design and construction of landfills. The latter application has been triggered by the economic and technical advantages that geosynthetics offer in Polymers 2020, 12, 1874; doi:10.3390/polym12091874 www.mdpi.com/journal/polymers
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