Predicting the Creep Behavior of High Density Polyethylene Geogrid Using Stepped Isothermal Method

The creep behavior of a high density; polyethylene (I-IDPE) geogrid used for soil reinforcement applications was evaluated using two accelerated creep tests: Tine-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) gerogrids. 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 degrees C and a dwell time of 10(4) seconds were found to he 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 (aid 20% of UTS, while secondary creep was defected 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.