Enhancing printability and mechanical performance of 3D printed magnesium phosphate cement through silica fume modification: Rheological, microstructural, and numerical insights

This study explores the modification of 3D printed magnesium phosphate cement (MPC) using silica fume (SF) from rheological, microstructural and numerical perspectives, with the aim of enhancing its printability and mechanical performance. Results demonstrate that the incorporation of SF improved the yield stress and viscosity by forming compact flocculation structures. For hardened 3D printed MPC, SF reduced its mechanical anisotropy by enhancing its interlayer bonding. Microstructural analysis reveals that SF refined pores, suppressed dittmarite formation and promoted the formation of magnesium silicate hydrated (M-S-H) phase at interlayers, which is critical for the interlayer bonding enhancement. A discrete element method (DEM) model validates the critical influence of interlayer bonding on anisotropic behavior and reveals the failure mechanism of 3D printed MPC loaded in different loading directions. This work bridges the gap between rheology control and mechanical anisotropy in 3D printed MPC, offering valuable insights for advancing additive manufacturing in construction. • Silica fume improves the yield stress and viscosity by forming compact flocculation structure. • Silica fume enhances the interlayer bonding and alleviate the mechanical anisotropy of 3D printed MPC. • M-S-H phase was detected at the interlayer interface. • The DEM model validates the critical influence of interlayer bonding on mechanical anisotropy.