Effect of Amorphous Alloy Fiber on the Mechanical Properties of Ultrahigh-Performance Concrete by Nano-SiO2 Surface Modification

Amorphous alloy fiber-reinforced concrete (AAFRC) demonstrates superior tensile strength and corrosion resistance compared to steel fiber-reinforced concrete. However, the weak interfacial bonding between amorphous alloy fiber (AAF) and the cement matrix limits its performance, necessitating surface modification. This study investigates the effect of nano-SiO2 surface modification on AAF and its influence on the mechanical properties of ultrahigh-performance concrete (UHPC). The results reveal that a 3% nano-SiO2 solution yields optimal fiber modification, achieving a surface roughness of 3.94, a contact angle of 5.653°, and an interfacial bond strength of 3.37 MPa with the cement matrix. After modification, the UHPC incorporating treated fibers exhibited significant improvements in mechanical performance, with compressive strength, flexural strength, tensile strength, and peak stress reaching 134.4, 25.9, 8.51, and 119.27 MPa, respectively. These values represent increases of 3.54%, 7.92%, 13.47%, and 8.9% compared to UHPC with unmodified fibers. Microstructural analysis indicates that the nano-SiO2 coating reacts with cement hydration products, consuming Ca(OH)2 and generating additional C-S-H gel, thereby enhancing the fiber-matrix interface and overall mechanical performance. The findings provide a practical approach to optimizing AAF reinforcement in UHPC applications.