# Experimental Study on Mechanical Properties of Graded EPS-Steel Fiber-Reinforced Concrete
## 1 Introduction  
In modern municipal engineering, facilities such as roads, reservoirs, and firewalls place high demands on the mechanical properties of concrete. With the advancement of technology, the performance requirements for concrete in practical engineering have risen significantly. A key focus of current research is to improve the mechanical propertiesof concrete while minimizing its self-weight. This has become a major topic in the field today. EPS (expanded polystyrene) foam particles are a high-quality, eco-friendly building material that plays a significant role in enhancing the lightweight and thermal insulation properties of concrete. The use of EPS particles not only helps in reducing waste but also contributes positively to environmental management [1; 2; 3]. Research has shown that EPS foam particles can improve the water erosion resistance of concrete [4]. When EPS foam particles are used as admixtures to replace some of the components in concrete, the density of the concrete decreases, while its thermal insulation properties are enhanced, and its ability to buffer impact stress waves is significantly improved [5; 6; 7]. [PERSON] et al. [8; 9] incorporated 15% EPS particles into concrete, and their comparison revealed that this concrete mixture had a 24% reduction in weight compared with ordinary concrete. [PERSON] et al. [10] found that incorporating a certain volume fraction of EPS particles as aggregates into concrete reduced the material's thermal conductivity, thereby improving its insulation properties. To achieve the goal of reducing the self-weight of concrete while improving its mechanical performance, researchers have also investigated the addition of fiber materials to concrete, in conjunction with EPS particles, to further enhance its mechanical properties. [PERSON], [PERSON] et al. [11] studied the effects of fabric fibers (polyester fibers, polypropylene mesh fibers, and polyacrylamidefibers) as admixtures. [PERSON] et al. [12; 13; 14] conducted an in-depth investigation into the mechanisms by which graphene oxide-grafted carbon fibers, polyvinyl alcohol (PVA) fibers, and basalt fibers modify the mechanical properties of concrete. Utilizing X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques, they systematically analyzed the permeability resistance of concrete incorporating these fibers. Their research elucidated the synergistic mechanisms between the microstructural characteristics and macroscopic performance of fiber-reinforced concrete. Their research demonstrated that polyester fibers can effectively improve the compressive strength, splitting tensile strength, and flexural strength of concrete. [PERSON], [PERSON] et al. [15; 16] proposed, through constitutive models and experiments, that the inclusion of steel fibers in concrete results in improved bending toughness and provided an evaluation method for this property. To address the segregation phenomenon caused by the significantly lower apparent density of EPS particles compared with the density of the cementing materials in concrete, previous studies have used epoxy resins or water-soluble ethylene-vinyl acetate copolymers as binders, effectively resolving this issue [17; 18]. Although a considerable amount of research has been conducted on the relationship between EPS particles and the mechanical properties of concrete, most studies focus on the effects of EPS particles with a single particle size on the mechanical performance of concrete, typically using a single concrete grade and mix proportion for experimental investigations [19; 20]. In practical engineering, however, the application scenarios of concrete are diverse, and different concrete grades in various locations and working conditions impose distinct requirements on aggregate particle size and gradation. As a result, experimental findings based on a single concrete grade and mix ratio are often difficult to generalize.