Short-Term and Long-Term Behavior of EPS Geofoam

Expanded Polystyrene Styrofoam (EPS) geofoam is widely used in various civil engineering applications. To predict the responses of structures to external loading, when in the presence of geofoam, understanding physical and mechanical behavior of geofoam, both short and long term, is very essential. A series of laboratory experiments was conducted on EPS15, EPS20, and EPS25 geofoam specimens under different loading conditions. To understand the short-term behavior, static uniaxial compression and cyclic uniaxial compression (CUC) tests were performed; however, for long-term behavior, accelerated creep and pseudo long-term tests were conducted on geofoam samples. CUC tests were performed at different static and cyclic stress amplitudes and loading frequencies for 5,000 load cycles, and the results reveal that, irrespective of geofoam density, secant modulus (E-dyn) decreases and the damping ratio of geofoam increases with the increase in cyclic axial strain. Also, it was observed that an increase in cyclic axial strain and the number of loading cycles reduced the Poisson's ratio of geofoam from positive to negative values. From the time-temperature-stress superposition accelerated creep testing method, creep strains developed in EPS15, EPS20, and EPS25 geofoam samples at the end of 100 years were 2.12, 2.4, and 2.11 %, respectively. From pseudo long-term tests, the estimated Young's modulus (E) of geofoam decreases with the increase in compressive creep strain for all three densities of geofoam.