Performance and macrostructural characterization of 3D printed steel fiber reinforced cementitious materials

The widespread adoption of Construction 3D Printing (C3DP) for structural applications has been hindered by the lack of seamless integration of reinforcement into the automated layering process. Incorporating steel fibers into the printing material could eliminate technical complexities associated with other proposed reinforcement methods for C3DP. This study investigates the fresh and hardened-state properties of printing mixtures including different dosages of steel fibers, especially high dosages which have not been investigated before. This study also considers the effects of other parameters such as sand-to-powder ratio and the limestone content on the properties of steel fiber reinforced printing materials, to reduce the Portland cement content which has a high carbon footprint. The obtained experimental results revealed that high-performance materials incorporating up to 2.5% steel fibers (by volume) can be successfully 3D printed. The mechanical properties of the reinforced mixtures improved significantly at high fiber dosages (2% and 2.5% vol.). The CT-scan results reveal that the orientation and alignment degree of steel fibers in the composite is affected by different parameters such as the binder content and nozzle design. Based on the significant improvement in the tensile properties reported in this study (e.g. up to 148% increase in tensile strength), incorporating high dosages of steel fibers can be an effective C3DP reinforcement technique for structural applications.