Influence of Paste Strength on the Strength of Expanded Polystyrene (EPS) Concrete with Different Densities

Concrete in which EPS (expanded polystyrene) particles partially or completely replace concrete aggregates is called EPS concrete. Compared to traditional concrete, EPS concrete has a controllable low density and good thermal-insulation performance, which make it promising for prospective applications. At present, research on EPS concrete mostly focuses on increasing its strength and EPS surface modifications. Few researchers have studied the influence of cementitious material strength and EPS-concrete density on the strength of EPS concrete. In this research, cement was used as the main material, and fly ash, silica fumes, and blast furnace slag were selected as admixtures. By changing the mixing proportions of the admixtures, the basic properties, such as the paste strength, change. Based on the mix proportions of the above different raw materials, EPS concrete with different density levels was prepared to explore the influence of the density of EPS concrete and the strength of cementitious materials on the strength of EPS concrete. The influence of the slurry strength on EPS-concrete strength was weaker than that of the density of EPS concrete. When the strength range of the cementitious materials is 35.7~70.5 MPa, the compressive strength range of 1000 kg/m³, 1200 kg/m³, and 1400 kg/m³ EPS concrete is 8.8~17.6 MPa, 11.4~18.0 MPa, and 15.7~26.6 MPa, respectively. Based on the experiments, the fitting equation to determine the EPS-concrete strength–EPS-concrete density–cementitious material strength is z = 69.00087 + 0.0244x − 0.1746y − 0.00189x² + 0.0000504706y² + 0.00028401xy. Additionally, a strength-increasing design method for EPS concrete with different densities prepared by conventional Portland cement is clarified. This study can guide the preparation of EPS concrete.