Multiscale Analysis of EPS Concrete Strengthened by Synergistic Reinforcement of Styrene–Butadiene Latex and PVA Fibers: Experiments and Molecular Dynamics Simulations

Abstract

Expanded polystyrene (EPS) concrete is a new typical composite concrete, but its material toughness and hydrophilicity are poor, leading to low strength and poor toughness. To solve this critical issue, this study used an interactive method of experimentation and simulation to systematically study the mechanism of how the synergistic strengthening of styrene–butadiene latex (SBL) and polyvinyl alcohol (PVA) fibers improves the performance of EPS concrete from the macro, micro, and nano multiscale systems. Macromechanical tests showed that the mechanical properties of EPS concrete are obviously improved by adding PVA and SBL. PVA fiber can reduce the compressive strength of EPS concrete but increase the flexural strength. The addition of SBL has a positive effect on the anticompression and flexural properties. Observation and analysis of microexperiments using electron microscopy, X-ray diffraction, and infrared spectroscopy showed that the addition of SBL improved the weak interface zone, increased the hydration crystallinity of unhydrated cement products, and formed a more abundant cement-based gel to fill weak cement pores, resulting in a more uniform and stable internal structure. At nano scale, the molecular dynamics interface models of EPS/calcium silicate hydrate (C-S-H), EPS/SBL/C-S-H, PVA/C-S-H, and PVA/SBL/C-S-H were established and simulated and analyzed at the nanoscale. The results showed that the addition of SBL played a crucial role in connecting organic polymers with inorganic silicates in a “bridge” form. It formed numerous hydrogen bonds and ionic bonds with EPS, PVA molecular chains, and C-S-H, effectively stabilizing the crystalline layer structure of hydrated calcium silicate and compensating for the weak hydrophilicity of EPS particles, making the EPS/C-S-H and PVA/C-S-H systems more tightly stable. Expanded polystyrene (EPS) foam concrete, with its advantages of ultralightweight, easy construction, and environmental friendliness, has been widely used in the construction industry. It finds applications in load-bearing precast concrete components, thermal insulation boards, cushioning or structural insulation boards, composite floors, pavement substrates, building envelope structures, and offshore floating structures, among others. These structures possess high strength, excellent insulation performance, high fire resistance, good water repellency, affordability, and strong sound absorption and noise reduction capabilities. However, the hydrophobic nature and porosity of EPS material result in uneven stratification and segregation during the preparation of EPS particles, as well as the existence of numerous weak interface transition zones between EPS and cement-based materials. In order to further expand its prospects in engineering applications and meet the requirements of modern engineering, it is necessary to enhance the workability and mechanical performance of EPS concrete. This study combines experiments and simulations to investigate the mechanisms and methods for reinforcing EPS concrete from a multiscale and multiangle perspective, providing references for the preparation of more stable and high-performance EPS concrete.