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Lifetime predictions of exposed and nonexposed geosynthetics

January 3rd, 2014 / By: / Industry News

Geosynthetic Institute’s webinar no. 8.

Wednesday, Jan. 8, 2014
11:30 a.m.–1 p.m. (EST)
GSI members $200 (USD) per webinar
Non-GSI members $250 (USD) per webinar

Background

A recurring question regarding all types of geosynthetics: “How long will they last?”
This webinar addresses the question from both exposed and nonexposed perspectives. It uses, for incubation purposes, laboratory ultraviolet fluorescent tube weathering devices to simulate exposed conditions.

Fifteen geosynthetic materials are evaluated: six geomembranes, two geogrids, four turf reinforcement materials, and three geotextiles. Each have been incubated at 80°C, 70°C, and 60°C until halflife of strength retained and elongation retained have occurred. The data is then extrapolated down to 20°C for laboratory halflife values. The calculations then progress to using site-specific radiation to obtain the equivalent field life. Arizona conditions are illustrated although the procedure is applicable worldwide.

The nonexposed conditions are evaluated based solely on a high-density polyethylene (HDPE) geomembrane and uses landfill incubation cells at four elevated temperatures. Using full depletion of antioxidants, induction time, and halflife at 20°C, the total lifetime is obtained.

The approximate lifetime for this geomembrane is 440 years. Since the incubation times took 12 years, other nonexposed geosynthetics were not evaluated with the conclusion that the buried (nonexposed) situation is a moot point for most geosynthetics and their respective applications.

Objectives

Webinar participants will gain familiarity of how lifetime prediction 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. The technique is called time-temperature-superposition followed by Arrhenius modeling.

The webinar is a result of more than 12 years of research by the Geosynthetic Institute/Geosynthetic Research Institute (GSI/GRI) that focused on providing lifetime estimates of geosynthetic materials.

For the exposed situation, laboratory fluorescent ultraviolet weathering devices are used. For the nonexposed (buried) situation, complete laboratory simulation is used. The former evaluates 15 different geosynthetics, the latter only HDPE geomembranes.

The exposed situation lifetimes are within the usual civil engineering lifetime expectations. For the nonexposed situation, lifetimes are well beyond civil engineering application lifetimes, in this case 440 years.

Benefits

  • Learn about lifetime prediction methods for polymers.
  • Learn specifically about the methodology with respect to geosynthetics.
  • Examine the lifetimes of 15 different geosynthetics under simulated exposed conditions.
  • Understand the large increase in lifetime when geosynthetics are nonexposed (i.e., buried).
  • Understand that lifetime of nonexposed geosynthetics are generally far greater than typical civil engineering applications and other components.

Audience

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.

Specific topics during this webinar include: exposed lifetimes using weathering devices, results for 15 different geosynthetic materials, nonexposed lifetime via lab simulation, results for HDPE geomembranes, summary to date.

Instructor

Dr. Robert M. Koerner is professor emeritus in civil engineering at Drexel University and director emeritus of the Geosynthetic Institute. His interest in geosynthetics spans across 35 years of teaching, research, writing, and advising.

Dr. Koerner has authored and co-authored more than 600 papers on geosynthetics and geotechnical topics in journals and at national and international conferences. His most widely used publication is the sixth edition of the textbook Designing with Geosynthetics.

Bob is the founding director of the Geosynthetic Institute, a nonprofit research and development organization dedicated to the proper use of geosynthetics in its myriad applications. The institute also provides laboratory accreditation and inspection certification programs.

Source: GSI

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