Strain rate effects on the compressive and tensile behavior of bundle-type polyamide fiber-reinforced cementitious composites

摘要

The compressive and tensile behavior of fiber-reinforced cementitious composites is significantly affected by the bonding and pull-out properties between matrix and reinforced fiber, as well as the fracture properties of the fibers. In addition, an increase in strain rate according to loading conditions influences the fracture behavior between the fiber and matrix. Steel fiber-reinforced cementitious composites with high flexural and tensile strength, toughness, and crack resistance are widely used in tunnels and plant structures. However, the high specific gravity and stiffness of steel fibers can cause rupture of concrete pump tubes, increase the rebound volume of shotcrete, and decrease durability by corrosion of fiber. Therefore, it is necessary to study the development and application of organic fiber which has similar mechanical properties to steel fiber and does not cause corrosion. In this study, polyamide fibers having the same aspect ratio as the hooked steel fibers, which are widely used as reinforcing fibers for concrete, have been developed. And strain rate effect on the compressive and tensile behaviors of bundle-type polyamide fiber-reinforced cementitious composite and hooked steel fiber reinforced cementitious composite were evaluated. The results showed that the effect of strain rate over different fiber types influenced the tensile behavior more significantly than the compressive behavior. In polyamide fiber reinforced cementitious composite (PAFRCC), a fracture behavior of fiber was observed regardless of a strain rate, and the tensile behavior of PAFRCC was influenced more by tensile strength of polyamide fiber itself than a bonding stress between fiber and matrix. In hooked steel fiber-reinforced cementitious composite (HSFRCC), a bonding stress between hooked steel fiber and matrix (frictional force at the interface between fiber and matrix, mechanical bond of the hooked part) influenced the tensile behavior significantly. Fracture properties that straightened pulled out the fiber from the matrix were observed at static tensile loading condition. However, non-straightened hooked steel fiber was observed along with the fracture of matrix due to an increase in mechanical bonding force of the hooked part and the bonding stress between the fiber and the matrix.