Tailoring of polyethylene fiber surface by coating silane coupling agent for strain hardening cementitious composite

Polyethylene (PE) fiber is a common material for preparing ultra-high-strength strain hardening cementitious composites (SHCC). However, the interfacial bonding between fiber and matrix is weak due to the hydrophobic nature of the PE fiber surface and resulting in low PE fiber utilization. In this study, a method is proposed by applying silane coupling agents (SCA) coating to the fiber surface to enhance the interfacial bonding and further improve the mechanical properties of PE fiber reinforced SHCC. The KH172 is proved to be the best one in five selected SCAs for PE fiber surface modification by surface energy analysis. The coating feasibility and hydrophilicity of SCA coated PE fiber are verified by the infrared absorption test and contact angle test, respectively. The effectiveness of this approach is evaluated by means of the single fiber pullout test and uniaxial tensile test. With the SCA coating, the interfacial fractional bond between fiber and matrix is increased by 52%, and the slip hardening response is remarkable. The ultimate tensile stress and tensile strain capacity of PE fiber-reinforced SHCC are increased by 48% and 112%, respectively. Based on the micromechanical analysis, the mechanism of composite property improvement due to interfacial enhancement by fiber surface SCA coating is demonstrated, and one of the greatest advantages of this approach is the saving on the dosage of fiber.