Ultrafast-setting magnesium phosphate cement prepared from low-burned magnesium oxide for mixed stirring extrusion function integrated 3D printing applications

Regarding the issues of high cost, energy consumption and low activity in the existing preparation of magnesium phosphate cement (MPC) using heavy-burned magnesium oxide as raw material, this paper aims to prepare ultrafast-setting MPC using low-burned magnesium oxide. The objective was to explore the laws and mechanisms by which different magnesium oxide calcination temperatures affect the setting time, compressive and bond strengths, volumetric stability, and microstructure of MPC, thereby determining the optimal calcination temperature of magnesium oxide. Then, taking the setting time and compressive strength as performance indices, this paper determines the optimal baseline values of each component of MPC. Specifically, it ascertains the magnesium-phosphorus ratio, water-binder ratio, and borax doping amount. Subsequently, it integrates with the Mixed Stirring Extrusion Function Integrated 3D (MSEFI-3D) printing process to realize the application of MPC. The results reveal that, in comparison with MPC prepared from traditional heavy-burned magnesium oxide, appropriately reducing the calcination temperature of magnesium oxide can effectively enhance the mechanical properties of MPC and improve its volume stability. The compressive strength and interfacial bonding strength of MPC reach their optimal values when the calcination temperature of magnesium oxide is within the range of 850–950°C. Furthermore, the MPC prepared at this calcination temperature demonstrates excellent extrudability and constructability during the printing process. It can satisfy the requirements of 3D printing, thus providing a reference for the 3D-printing application of ultrafast - setting MPC prepared from low - burned magnesium oxide.