Neodymium magnets for orientation of steel fibers in concrete: Physical properties, mechanical behavior and image analysis

Abstract

This study explores how the magnetic orientation of steel fibers influences the physical and mechanical properties of a steel fiber reinforced concrete beam. A set of neodymium magnets coupled to a robotic arm was used to guide the metallic fiber reinforcement within the coarse cementitious matrix. Radiographies of portions of the specimens were used to access the fiber distribution across the hardened specimens. The physical properties were assessed through electrical resistivity, while mechanical behavior was evaluated by compression and three-point bending tests. Fiber counting was used to assess the influence of the notching process on the amount of reinforcement present in the fractured sections of the beams in both random and oriented conditions. Results showed that it is possible to optimize the spatial arrangement of macro metallic fibers in concretes containing coarse aggregates. The orientation of the reinforcement resulted in a decrease in electrical resistivity along the magnets' displacement axis (>80 % average reduction at the base of the prisms). Composites with oriented reinforcement showed on average 24 % more fibers crossing the fractured region than random ones. Furthermore, specimens with oriented fibers exhibited, in general, improved flexural performance and toughness compared to those with random reinforcement. This research highlights a novel approach that can enhance the efficiency and sustainability of steel fiber-reinforced concrete applications.