Active Control of Steel Fiber Orientation in Three-Dimensional Concrete Printing

Description

Three-dimensional concrete printing (3DCP) is an advanced additive manufacturing technique that has garnered significant attention, owning to its ability to eliminate the need for formwork and provide great freedom in creating personalized structures. Thus, 3DCP has the potential to revolutionize the construction industry by increasing efficiency, reducing labor and costs, and minimizing material wastage. To enhance the mechanical properties of printed structures, steel fibers exhibit significant promise because they align along the printing direction during the extrusion process. However, the fibers remain randomly distributed in other directions, with limited bridging between adjacent layers. Additionally, the 3D printing of concrete with steel fibers poses the risk of nozzle blockage, particularly at higher fiber volumes and smaller nozzle sizes.This proposed project will address these challenges by using a magnetic field to actively control steel fiber alignment in 3D printing concrete. This approach will minimize fiber clogging through the adjustment of steel fiber orientation in the flow direction, and meanwhile, improve the buildability and ductility of printed structures by uniformly aligning fibers in filaments. This will be achieved by characterizing the changes of steel fiber distributions and rheological, microstructural, and mechanical properties of steel fiber reinforced concrete (SFRC) in response to a magnetic field. Moreover, the magnetic field-induced flow behavior and extrudability of SFRC will be assessed using a custom pipe/nozzle device. Consequently, the relationships between steel fiber distributions, magneto-induced flow behavior, and rheological response will be established. This will allow determination of the mechanisms whereby the magnetic field and the extrusion process synergistically affect steel fiber alignment and buildability. In addition, the mechanical properties and layer-interface characteristics of 3D printed structures with magneto-induced steel fiber alignment will be determined. Ultimately, an approach for the active control of steel fiber orientation in 3D printing concrete will be devised, and a magnetic nozzle prototype will be developed for experimental validation.The novelty of actively controlling steel fiber orientation using a magnetic field lies in its non-contact and post-control nature. This enables the manipulation of material flow without affecting the pumping process, allowing for tailoring of both extrudability and buildability of the same concrete mixture. The proposed project outcomes will improve the overall quality of 3D printed concrete structures and facilitate the emergence of four-dimensional (4D) concrete printing. The knowledge gained will support the structural application of 3DCP in the construction industry, thereby contributing to sustainability and carbon neutrality goals.