Assessing printing synergism in a dual 3D printing system for ultra-high performance concrete in-process reinforced cementitious composite

3D printed ultra-high performance concrete (3DP-UHPC) acting as the reinforcement to in-process reinforce 3D printed concrete (3DP-C) can significantly improve the load-bearing capacity of 3DP-C. This method (3DP-UIRC) is achieved via a dual 3D printing procedure in which 3DP-UHPC as inner core is wrapped by 3DP-C and extruded together. However, lack of printing synergism between 3DP-C and 3DP-UHPC in deposition parameters, such as deposition layer height, printing speed and deposition rate, may result in heterogeneity of composite materials, and thus negates the overall mechanical strength of the structure. Therefore, parameters of nominal proceeding error (NPE) and co-printing factor (CF) are suggested to characterize the simultaneous manufacturing precision of 3DP-UIRC. The two suggested indicators are practically geometrical parameters to reflect the 3D concrete printing quality. Correspondingly, the printing precision error e and area ratio r are defined based on the experimentally measured values for comparison with NPE and CF, respectively. The printing precision error e and the area ratio r are calculated to be 0.37 and 0.163 by evaluating the practical syncing printing results with different layer height and extrusion volumetric flow rates of 3DP-C and 3DP-UHPC. They are approximately equal to NPE of 0.4 and CF of 0.16 with deviations of 7.5% and 2.5%, respectively. This study provides a new concept and quality assessment method for simultaneous printing of 3DP-UIRC. It also provides ideas and sci-entific references for promoting the application of 3DP-UIRC in 3D printing structured applications.

Automated summary

3D printed ultra-high performance concrete (3DP-UHPC) can be used to reinforce 3D printed concrete (3DP-C) and improve its load-bearing capacity. However, the lack of printing synergism between 3DP-C and 3DP-UHPC may result in heterogeneity and reduce the overall mechanical strength of the structure. To address this issue, the study suggests using nominal proceeding error (NPE) and co-printing factor (CF) as indicators to characterize the manufacturing precision of the reinforcement method. The study also provides a new concept and assessment method for simultaneous printing of 3DP-UHPC.