The Influence and Mechanism of Polyethylene Fiber Characteristics on the Mechanical Properties of High-Strength Engineered Cementitious Composites

This study investigates the impact of fiber characteristics on high-strength engineered cementitious composites (HS-ECC) and its microscopic mechanism. Five groups of ultra-high molecular weight polyethylene fiber (PE fiber) were systematically designed to explore their effects on the mechanical properties of the composites, including 12 mm reference fibers, 18 mm length fibers, 2.0% content fibers, surface-treated fiber, and fibers from various manufacturers. The mechanical properties of the composites were assessed through compression, tension, three-point bending, single-crack tension, and electron microscope scanning. The test findings reveal that, in comparison to the 12 mm reference group, the compressive strength of the latter four groups with alternative fiber characteristics demonstrates enhancement. Notably, the 18 mm fiber length leads to a substantial increase in crack quantity and reduction in crack width, with the crack width measured at a mere 31 µm. The introduction of SK71 fiber significantly alters the matrix's microstructure, thereby yielding the highest tensile strain capacity of 7.45% among the experimental groups. Conversely, the tensile strain capacities of the surface-treated and 2.0% fiber content test groups are found to be 2.25% and 2.28%, respectively, due to the poor fiber dispersion within the microstructure. All experimental groups satisfy the dual criteria for strength and energy, achieving a tensile strain hardening state. The findings from this study provide valuable insights for the selection of fibers in the preparation of HS-ECC.