The Geosynthetic Institute (GSI) will sponsor a webinar entitled “Lifetime Predictions of Covered and Exposed Geosynthetics,” on November 28, from 11:30 a.m. to 1 p.m. EDT. GMA member companies and their employees receive discounted rates on all GSI webinar and short course registrations.
A most frequently asked question regarding all types of geosynthetics is, “How long will they last?” This webinar answers the question for exposed geotextiles and geomembranes assuming that they were properly designed and installed. Furthermore, it compares these new results to earlier lifetime prediction results on a covered geomembrane.
Nonexposed (or covered) lifetime conditions have been previously evaluated and published on a 1.5-mm thick high-density polyethylene (HDPE) geomembrane. It used landfill incubation devices at four elevated temperatures of 85, 75, 65 and 55°C to reach 50% of retained strength and elongation. Considering the three stages of (i) depletion of antioxidants, (ii) induction time, and (iii) 50% reduction in mechanical properties, the lifetime extrapolation was made down to 20°C. The half-life for this geomembrane under these conditions is 450 years. Since the incubation times were 10 years, other covered geosynthetics were not evaluated under the supposition that the nonexposed situation is generally a moot point for most geosynthetics in their customary applications.
For exposed geosynthetics, however, the situation is quite different. Ultraviolet radiation, elevated temperature and full oxygen are available, which shorten the service lifetime, but how much? For evaluation of this situation we utilized laboratory ultraviolet fluorescent tube weathering devices per ASTM D7238 for incubation purposes. Seven different geotextiles, four turf reinforcement mats (TRM), two geogrids and six geomembranes were evaluated. Each different material was incubated at 80, 70 and 60°C until 50% reduction of strength and elongation occurred. The data was then extrapolated down to 20°C for laboratory half-life values and for comparison with the nonexposed condition. The ratio of nonexposed to exposed lifetime for HDPE geomembranes is approximately 5.0. The calculations for the nineteen exposed geosynthetics then progressed to using site-specific radiation to obtain an equivalent field life. Phoenix, Ariz., conditions are illustrated although the procedure is applicable worldwide. Half-life predictions for the geotextiles vary from a few months for the needlepunched nonwovens to up to 10 years for monofilaments and high antioxidant formulated products. Results for geomembranes vary from 47 to 97 years with HDPE being the highest. These exposed half-life results (which were analyzed over 12 years and are still ongoing) are felt to be most interesting and are presented for the first time to an international audience.
Webinar participants will gain familiarity of how lifetime predictions of all polymeric materials are made, including geosynthetics. The technique is incubation at several high temperatures to accelerate degradation, measure property changes and then to extrapolate down to site-specific (i.e., actual) temperatures to estimate lifetime.
This webinar will be beneficial for public and private regulators and facility owners, civil and industrial engineers, property developers, contractors and installers, academic and research groups, the general lay public, and others desiring technically related information on this most frequently asked question.
The webinar’s instructor, Dr. Robert M. Koerner, is professor emeritus of civil engineering at Drexel University, and founder and director emeritus of the Geosynthetic Institute.
Webinars cost $200.00 for GSI and Geosynthetic Materials Association (GMA) members, and $250.00 for nonmembers. Successful completion of a multiple-choice test after the webinar carries 1.5 professional development hours (PDH).
For more information or to register, visit http://www.geosynthetic-institute.org/webinar.htm.