Mechanism analysis of the magnetic field assisted 3D printed steel fiber reinforced concrete

The magnetic orientation of steel fibers in concrete, extensively studied in formwork-cast concrete for improving crack-bridging capacity, has yet to be analyzed for its feasibility in adjusting fiber orientation via magnetic field in 3D printed concrete. This study thus aims to propose a technique for in-situ magnetization of steel fibers and quantitatively investigate fiber magnetic orientation in 3D printed concrete. Relations between critical process parameters and the fiber magnetic orientation were investigated, including magnetic induction intensity, fiber volume fraction, and fiber types. The results reveal that when the magnetic induction intensity at the center of the nozzle reaches 34mT and the fiber volume fraction is 0.5%, 25 mm bow steel fibers (BF25) exhibit the most significant effect on bridging cracks, with a maximum improvement in mechanical properties of over 50 %. The enhancement of the mechanical properties demonstrates the huge potential of applying fiber magnetic orientation in 3D printed engineering concrete.