Strengthening fiber/matrix interfacial bond in high strength ECC through modifying PE fiber with nano-CSH seeds

Polyethylene (PE) fibers are widely utilized in high-strength engineered cementitious composites (ECC) owing to their exceptional mechanical properties. Nevertheless, the marked hydrophobicity of PE fibers substantially weakens the fiber/matrix interfacial bonding strength, thereby restricting the effective mobilization of bridging stress capacity. To mitigate this limitation, this study employed nano-CSH seeds for PE fiber surface modification and investigated their efficacy in enhancing the tensile performance of ECC mixtures. Microstructural characterization revealed that nano-CSH seeds formed a uniform, dense coating on PE fibers, substantially improving surface hydrophilicity. Uniaxial tensile tests demonstrated that ECC incorporating modified PE fibers exhibited 37% and 54% increases in tensile strength and tensile strain capacity, respectively. Compared to the ECC with unmodified fibers, ECC with modified fibers displayed reduced average crack width, increased the number of crack, and enhanced strain-hardening behavior. The nano-CSH seeds modification improved the interfacial frictional bond by 41%, effectively reinforcing PE fiber bridging stress. This proposed modification strategy not only offers a facile yet effective approach for optimizing the strain-hardening behavior of ECC but also provides critical insights for advanced high-strength ECC design.