Rheological and Mechanical Properties of 3D-Printable Magnesium-Oxysulfate-Cements (2025-02)¶

Magnesium oxysulfate cement (MOS) offers a promising alternative to 3D-printed Portland cement due to its rapid hardening and high strength. The layer-to-layer interfacial bonding of the 3D printed specimen is closely related to the rheological performance of fresh mixtures. This paper investigates the influence of rheological properties on the printability and mechanical performance of 3D printable magnesium oxysulfate cement (3DP-MOS) paste. The results show that an increase in the magnesium-to-sulfur ratio reduces fluidity and lowers the minimum water content of MOS mortar, enhancing packing density, accelerating early hydration, and improving printability, extrusion stability and structural integrity. MOS mortar with a molar ratio (MgO: MgSO4·7H2O: H2O) of 15:1:12 or 21:1:15 demonstrates optimal flow performance and setting time. Dynamic yield stress values ranging from 587.9 to 888.7 Pa and a consistency factor of 2.0–36.8 in 3DP-MOS mortar ensure stable extrusion width and stacking height, closely aligning with the intended design and ensuring both precision and structural integrity in 3D-printed structures. Additionally, higher dynamic yield stress and a lower consistency factor promote uniform deposition and a denser microstructure in 3D-printed MOS materials, enhancing mechanical properties.