Mechanical Properties of EPS Geofoam Under Various Loading Conditions

Abstract

This study presents experimental studies on EPS geofoam using cyclic uniaxial compression (CUC), accelerated creep and pseudo-long-term tests. For all experiments 100 mm cube geofoam samples of 15 kg/m3 density (EPS15) are used. Servo-hydraulic actuator and temperature regulated water chamber (TRWC) are used. CUC tests are performed at two loading frequencies 0.5 and 3 Hz, R values of 0.4, 0.6, 0.8, 1 and 1.2 and 5000 loading cycles. Term ‘R’ defined as ratio of combined axial static and cyclic stress component to the yield strength of geofoam. To understand creep behavior of geofoam Time temperature stress superposition (TTSS) accelerated creep testing method is adopted. Master creep curve is developed for a designed strength of 20% compressive strength (σ c ) and reference temperature of 29 °C. From CUC tests it is observed that effect of number of cycles is insignificant on secant modulus (E dyn ) compared to R and loading frequencies. Also, Poisson’s ratio (υ) is observed to vary from positive to negative, and it majorly depends on R values and number of cycles. From TTSS method 2.12% compressive creep (CC) strain is observed at 100 years for EPS15 geofoam. Pseudo-long-term tests are performed at various CC intervals and it is noted that Young’s modulus (E) decreases with increase in CC. E, compressive strength and yield strength of CC sustained samples are decreased from that of initial or non-CC sustained samples. Moreover, Young’s modulus of geofoam reduces with time.