Experimental Study of the Static and Dynamic Characteristics of Lightweight EPS Composite Soils Treated with Cement

Expanded polystyrene (EPS) beads mixed with soil and cement are a new type of artificial lightweight fill material used in geotechnical practices. Hence, it is necessary to adopt an exhaustive procedure for evaluating the EPS composite attributes. In this study, Firoozkuh No. 161 sand was treated with portland cement and EPS beads, and the results of the two types of tests were combined to recommend the best mix ratio for geotechnical applications. Unconfined compression tests were carried out to investigate the mechanical characteristics of EPS composite and specify the optimum scope for EPS, cement, and water contents that were used in the strain-controlled cyclic experiments. Moreover, cyclic triaxial tests were conducted to evaluate the influence of mixing ratios, confining pressure, strain level, and the development of modulus reduction curves. The results indicate that increasing the cement content by 4%–6%, along with EPS beads up to 10% in volume, significantly enhances the composite's uniaxial compressive strength and shear modulus at higher strain levels. According to the results, there is a small variation in the damping ratio caused by cementation, which indicates that cement percentage has a greater impact on the damping ratio of the mixture than EPS beads.