On use of polyvinylpyrrolidone to modify polyethylene fibers for improving tensile properties of high strength ECC

Polyethylene (PE) fiber is widely used in high strength engineered cementitious composites (ECC) due to its exceptional mechanical properties. However, the strong hydrophobicity of PE fibers hinders the bonding between fibers and matrix. To enhance the interfacial bond and fully utilize the reinforcing effect of PE fiber, this study employed polyvinylpyrrolidone (PVP) to modify the surface of PE fiber. The improvement effect of various PVP solution concentrations on ECC behavior was investigated. The microscopic characterization tests revealed that the surface of PE fibers was effectively coated by PVP, and the hydrophilicity of PE fibers was significantly improved after modification. Uniaxial tensile tests demonstrated that after PVP modification, the tensile strength and ultimate tensile strain of ECC increased by 20.7-27.2% and 87.3-109.3%, respectively. Furthermore, the ECC with modified PE fibers exhibited a decrease of 10-20% in the average crack width, coupled with a nearly twofold increase in the number of cracks, compared to the pristine ECC specimens. At microscale, the single fiber pull -out tests demonstrated that the interfacial frictional bond between fiber and matrix was effectively enhanced after PVP modification. The proposed method of modifying PE fibers surface with PVP offered a simple and environmentally friendly approach to enhance the strain hardening behavior of ECC, which provided valuable insights for optimizing the design of high strength ECC.