Enhancing the performance of ultra-high-performance concrete using dendritic fibrous FeNi₃ nanoparticles: A magnetically active and structurally reinforcing additive

This study introduces a novel approach for enhancing the multifunctionality of lightweight cementitious composites by incorporating magnetically responsive fibrous FeNi₃ nanoparticles (DF FeNi₃). The unique fibrous morphology of the synthesized FeNi₃ nanoparticles not only improves the dispersion and interfacial bonding within the cement matrix but also enables external field-assisted alignment, reducing agglomeration and promoting homogeneous microstructure. Detailed physicochemical characterization confirmed their high crystallinity, soft magnetic behavior, and superparamagnetic-like response, enabling efficient control during the mixing process. The addition of DF FeNi₃ significantly improved fresh-state rheology, flow retention, and workability. In hardened-state performance, the modified concrete exhibited enhanced compressive and flexural strength, reduced porosity, and improved resistance to freeze thaw cycles, sulfate attack, and acid degradation. Furthermore, UV-responsive hydrophilicity and methylene blue photodegradation confirmed the self-cleaning capability of the DF FeNi₃-modified composites. Magnetic hysteresis and contact angle analyses demonstrated that DF FeNi₃ acts as a smart dual-functional additive, offering both structural reinforcement and external stimulus responsiveness. These findings highlight the potential of DF FeNi₃ nanoparticles in developing smart, durable, and self-sustaining lightweight concrete systems for advanced construction applications in harsh and aggressive environments.