A new EPS beads strengthening technology and its influences on axial compressive properties of concrete

In this article, a new technology of surface wrapping and strengthening of expandable polystyrene (EPS) beads is proposed. Three wrapping materials including magnesium phosphate cement (MPC), ultra-high performance concrete (UHPC), and water-borne polyurethane (WPU) were evaluated. Four groups of uniaxial compression tests of EPS concrete specimens were conducted: the failure process and the characteristics of the specimens were analyzed; and the complete stress-strain equation is proposed based on these analyses. The research shows that the EPS beads were strengthened by wrapping, and the axial compressive strength of concrete is increased by 50-75%; the concrete with EPS beads wrapped by MPC and WPU has obvious brittleness; the concrete with EPS beads wrapped by UHPC has axial compressive strength close to that of EPS concrete wrapped with MPC and WPU but has a larger ductility coefficient (150%), a larger toughness coefficient (50-90% larger), a higher energy dissipation coefficient (40% larger), and larger residual stress. The proposed stress-strain model is in good agreement with the experimental results, which can accurately describe the stress and deformation characteristics of EPS concrete under uniaxial compression and has good applicability. The discovery of this study provides background knowledge for the structural analysis and design of this kind of concrete; it provides a basis for selecting EPS concrete as structural materials.