Comparative investigation of normal and hydrophilic functionalized nylon and aramid fibers as fiber-reinforcements in mortar

Fiber-reinforcement technology not only enhances the tensile strength and ductility of concrete but also has gained attention in the field of concrete 3D printing as a potential alternative to traditional rebar placement. To date, most studies have focused on the use of steel fibers; however, issues such as corrosion and poor pumpability have been raised as limitations. As a result, recent research has begun to explore fiber reinforcement using polymer fibers with superior corrosion resistance and flexibility. Among various polymer fibers, nylon and aramid fibers are considered promising alternatives to steel fibers as reinforcement materials owing to their excellent alkali resistance, corrosion resistance, flexibility, and mechanical properties. However, research on fiber-reinforced concrete (FRC) using nylon and aramid fibers is limited compared with studies involving steel fibers, and most of the existing studies have primarily focused on parameter optimization based on fiber aspect ratio and volume fraction. In addition, because flexible polymer fibers are not suitable for geometric modifications to enhance mechanical interlocking, it is necessary to improve chemical bonding through surface functionalization. However, the impact of the functionalization of polymer fibers on the performance of FRC has been scarcely investigated. Therefore, this study analyzed the effect of hydrophilic functionalized nylon and aramid fibers on the mechanical properties of mortar. Based on experiments, the slump, compressive strength, splitting tensile strength, and modulus of rupture of fiber reinforced mortar incorporating both normal and modified nylon and aramid were compared. Additionally, XRD and SEM analyses were performed to examine the chemical changes and alterations in the microstructure. The experimental results showed that excessive hydrophilic modification leads to the formation of a loose matrix around the fibers, thereby reducing the bond performance of the fibers.