Abstract: This paper presents an experiment aimed at investigating the influence of blending PVA fiber and nano-SiO₂ on the fatigue resistance of concrete.The experimental specimens are divided into three groups: blending PVA fiber only (Group P),nano-SiO₂ only (Group S),and PVA fiber mixed with nano-SiO₂ (Group SP).Uniaxial compression tests were performed on the specimens subjected to multiple-cycle fatigue loading, and the resulting data were used to assess their fatigue resistance.The relative dymanic elastic modulus and compressive strength of specimens after the tests were taken as the assessment indices.Additionally,SEM was employed to observe and analyze the microscopic action mechanism.The findings reveal that all three concrete groups exhibit a notable improvement in fatigue resistance compared to ordinary concrete,although the manner of improvement differs.Group S demonstrates the most notable enhancement in concrete strength, while group SP effectively suppresses the development of internal degradation in concrete. In terms of the underlying mechanisms,PVA fibers enhance the tensile capacity between concrete elements,effectively reducing damage and failure under fatigue loads, thereby prolonging the concrete’s failure process.Nano SiO₂ participates in the reaction to generate C-S-H (calcium silicate hydrate) gel,filling the weak areas of the concrete and improving its compressive strength,thus raising the starting point of failure under fatigue loads.These findings provide valuable insights for the design of fatigue-resistant concrete structures.

Key words: concrete mixed PVA fiber and Nano-SiO₂, fatigue resistance, scanning electron microscope(SEM), microscopic mechanism