Shear behavior of EPS geofoam reinforced with polypropylene fiber

The EPS geofoam as a lightweight material has been widely used in recent years to boost the performance of geotechnical structures. Both the internal and external stability of the fills made by the EPS blocks should be met. Overlying concrete slabs and thick pavements or applying denser EPS blocks provide internal stability of EPS geofoam lightweight fills by reducing the internal vertical stress within the EPS blocks. As an alternative way, in this study, new composite material is introduced by using the polypropylene fiber to reinforce the EPS geofoam in the factory as an attempt to improve the mechanical properties of the EPS geofoam. The composite material was fabricated in different fiber contents by solidifying the mixture of fiber and geofoam beads using controlled heat and temperature. Then, the behavior of the composite was studied using a series of direct shear tests. The results show that including fiber leads to a rise in the shear strength and a significant decline in the compressibility of the reinforced EPS geofoam. For the geofoam reinforced with 80% fiber content, up to 23.3% increase in the shear strength and 57.6% reduction in the vertical displacement (Δz) were observed in the laboratory. In addition, while the change in the composite's cohesion is largely decreased, the friction angle of the composite shows an increasing trend with fiber content increase. A maximum of 12.6% reduction in the cohesion and 100% increase in the internal friction angle of the reinforced material were observed in the laboratory.