First Author: Dong Enlai, PhD Student (Class of 2023), School of Materials Science and Engineering, Southeast University

Research Focus: 3D Printing of Ultra-High Performance Concrete (UHPC)

DOI: https://doi.org/10.1016/j.conbuildmat.2025.139983

Research Background

3D printed concrete (3DPC), as an emerging intelligent construction technology for building structures, offers promising solutions to current challenges in the construction industry, including labor shortages, high labor intensity, low automation levels, and low efficiency. Despite these advantages, one of the main obstacles to the widespread application of 3DPC lies in reinforcement challenges—especially the design and realization of vertical reinforcement. Ultra-high Performance Concrete (UHPC) is renowned for its exceptional strength, toughness, and durability. Integrating UHPC into 3D printing processes offers potential solutions to the common limitations of conventional 3DPC structures, particularly in terms of flexural and shear strength, while reducing overall thickness, weight, and steel reinforcement requirements in structural designs.

Key Research Points

1. Developed a high-performance 3D printed UHPC based on fiber orientation design principles and applied it in a fire- and blast-resistant EV charging station.

2. Verified the feasibility of applying 3D printed UHPC to large-scale, reinforcement-free structural elements via finite element modeling (FEM) and in-situ progressive loading tests.

3. Conducted a comparative analysis between 3DP-UHPC structures and 3D printed reinforced concrete structures to provide design references.

Main Research Content

1. Theoretical Support

By optimizing rheological parameters, printing process parameters, and steel fiber characteristics, the researchers achieved enhanced fiber alignment within UHPC, significantly improving mechanical performance in the print direction and increasing the efficiency of fiber utilization.

Figure 1. Principle of fiber alignment in 3D printed UHPC

2. Factory Printing and Structural Load-Bearing Assessment

The optimized UHPC mix design allowed for continuous printing of large components, with each unit measuring 2.38 m in height, 2.8 m in base length, and 1 m in width. The entire printing process took 201 minutes. Using FEM simulations and in-situ progressive loading tests, the 3DP-UHPC structure was validated to withstand extreme weather loads as specified by the Chinese national code GB 50009-2012. Under a 4 kN/m² load, the deflection of the cantilevered upper structure remained within 1/250 of its span.

Figure 2. FEM simulation and load-bearing tests

3. Comparative Analysis of 3DP-UHPC and 3D Printed Reinforced Concrete Structures

Compared to conventional 3D printed reinforced concrete components, 3DP-UHPC demonstrated substantial advantages. It reduced structural weight by 40%, cross-sectional area by 83%, labor input by 50%, and construction time by 90%. Moreover, it increased the utilization of solid waste materials by sevenfold, improving overall sustainability.

Figure 3. Comparison between 3DP-UHPC and 3D printed reinforced concrete structures

Conclusion

The fiber-orientation-controlled 3DP-UHPC exhibits excellent mechanical performance. The proposed rebar-free UHPC components can withstand extreme climate-induced loads, while significantly reducing structural weight and construction time, and enhancing environmental sustainability. This study provides an innovative approach to reducing reinforcement in 3D printed concrete applications.