Predicting the creep behavior of high density polyethylene geogrid using stepped isothermal method

Abstract

The creep behavior of a high density polyethylene (HDPE) geogrid used for soil reinforcement applications was evaluated using two accelerated creep tests: Time-Temperature Superposition (TTS) and the Stepped Isothermal Method (SIM). TTS has become a well-accepted method to evaluate viscoelastic behavior of polymeric materials, while SIM is a relatively new accelerated creep test that was initially developed to evaluate polyethylene-terephthalate (PET) geogrids. However, the applicability of SIM has not been extensively studied for HDPE geogrids. In this chapter, variations in the three test parameters of SIM (i.e., temperature increment, dwell time, and applied load) were investigated. As recommended in ASTM D 6992, a temperature increment of 7°C and a dwell time of 104 seconds were found to be suitable for the testing of HDPE geogrids. On the other hand, a new analytical procedure was implemented to generate the creep master curve. The creep properties obtained from SIM and TTS were similar at 20 and 30% ultimate tensile strength (UTS). The geogrid exhibited primary creep at 10 and 20% of UTS, while secondary creep was detected at 30 and 40% UTS. Furthermore, the activation energies at different applied loads from both accelerated creep methods were determined and their values ranged from 140 to 200 kJ/mol. © Springer Science+Business Media, LLC 2009.