Enhancement mechanism of compressive plastic deformation properties in concrete induced by fiber spherical aggregates

To ensure the stability of coal roadway props, the roadside support filling material must not only provide sufficient strength but also exhibit significant compression deformation capacity. Traditional concrete, primarily used in the construction of roads, bridges, and housing, emphasizes strength design with little consideration for deformation performance, rendering it unsuitable for the ultra-high pressure plastic deformation demands of roadside support filling materials in mining areas. This study prepared fiber-reinforced spherical aggregates through granulation molding of freshly mixed cement slurry with embedded fibers, and examined the influence of fiber content and size on the cylinder compressive strength and compression deformation of the spherical aggregates. The mechanical and compressive plastic deformation properties of fiber spherical aggregate concrete (FSAC) were investigated through compressive strength, flexural strength, and stress-strain curves. Additionally, video electron microscopy and SEM analysis were employed to explore the internal mechanisms by which fiber spherical aggregates (FSA) enhance the compressive plastic deformation properties of concrete. The test results indicate that although the cylinder compressive strength of FSA is marginally lower than that of natural aggregate (NA), it exhibits exceptional plastic deformation capacity. With the increment in fiber content or size, the compressive strength of FSAC remains relatively unchanged compared to NAC. However, the flexural strength is markedly enhanced when the fiber content reaches 1.5 % and the fiber length is 9 mm. Unlike the brittle failure observed in natural aggregate concrete (NAC) after crushing, FSAC specimens maintain good integrity post-compression failure. Additionally, FSAC demonstrates higher peak stress and stable strain near the peak stress, indicative of pronounced plastic deformation characteristics. The plasticity change in FSAC primarily relies on the exceptional compression plastic transformation properties of the FSA, which convert point stress at aggregate contacts into flexible surface contact, thereby dispersing stress and enhancing the overall compressive deformation capacity of the concrete. •This study prepared fiber-reinforced spherical aggregates through granulation molding of freshly mixed cement slurry with embedded fibers, and examined the influence of fiber content and size on the cylinder compressive strength and compression deformati