Effect of water film and paste film thicknesses on printability of 3D printed low cement UHPC

To address the limitations of 3D printed concrete, such as low ductility and susceptibility to cracking, the development of 3D printed low cement ultra-high performance concrete (3DP-LC-UHPC) represents an effective approach. However, the complex and variable composition of this material makes it challenging to elucidate the relationship between composition and printability, which in turn constrains material design. In this study, the film thickness theory will be employed to establish the relationship between composition, structure, and printability of 3DP-LC-UHPC, utilizing water film thickness and paste film thickness as structural parameters. Correlations of the rheological properties to the water film thicknesses yielded R2 values of at least 0.9. The combined effect of water film thickness (WFT) and paste film thickness (PFT) on the printability (extrudability and buildability) of the material is significant, with a correlation coefficient of 0.85 between them. The feasibility of film thickness theory applied to optimize the printability of 3DP-LC-UHPC is verified and suitable ranges of WFT and PFT are recommended.