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This article compares two available approaches for accelerating the creep response of viscoelastic materials, such as High Density Polyethylene (HDPE), which is increasingly gaining attention for use in construction. Thermal acceleration methods to predict the tensile creep of polymers are already available. The TimeTemperature Superposition (TTS) phenomenon is the basis of several available methods, and an ASTM standard for tensile creep of geosynthetics is based on one of its derivatives, the Stepped Isothermal Method (SIM). In this article, both TTS and SIM have been adapted to study the compressive creep of virgin HDPE.An alternate approach, based on the equivalence of strain energy density (SED) between conventional constant-stress creep tests and strain-controlled stress-strain tests, is also adapted for accelerated compressive creep of HDPE. There is remarkably a good agreement among the creep behaviors obtained from conventional tests, TTS, SIM, and SED predictions for virgin HDPE.

Fiber reinforced polymer (FRP) composites represent an alternative construction material without many of the performance disadvantages of traditional construction materials. The use of FRP as a pile material can eliminate deterioration problems of conventional piling materials in water front environments and aggressive soils. Most of the available polymeric piling for light load applications is made of foamed recycled High Density Polyethylene (HDPE). A comprehensive understanding of the mechanical properties of foamed recycled polymers is essential for widespread use of polymeric piling. This paper presents the results of 178 compression tests conducted to assess the in-plane spatial distribution of the compressive strength of piling made of foamed recycled HDPE. Several methods were attempted to predict the stress-strain of the cross section from the compressive strength of small coupons extracted from within the cross section. Comparing the predicted behavior from coupon specimens to the measured behavior obtained by loading the whole cross section illustrates that the approach is promising.