Development and Characterization of Printable Rubberised Ultra-High-Performance Concrete (2025-06)¶

This paper introduces a printable ultra-high-performance fibre-reinforced concrete (UHPFRC) with an average 28-day compressive strength of 230 MPa and a maximum flexural strength of 31 MPa, which was achieved through extensive testing and adjustments guided by the theory of maximum packing density. Three types of printable UHPFRC mixes were assessed with 0%, 10%, and 20% rubber content. The basic properties were tested, including slump flow, rheology, printability, microstructure, compressive strength and flexural strength. By replacing 20% of the fine aggregate in equal volume with recycled rubber, the UHPFRRuC achieved an average 28-day compressive strength of 137 MPa and a maximum flexural strength of 22 MPa. In addition, this study proves that maintaining a minimum static yield stress of 250 Pa and a plastic viscosity of 20 Pa·s is crucial for ensuring good printability. Additionally, the distribution of steel fibres significantly influences the failure mode of UHPFRC specimens under static uniaxial compression, with fibres aligned parallel to the load direction (3DP-X) showing the highest compressive strength and most cracks. In UHPFRRuC, cracks tend to develop along the rubber particles. This study enhances the understanding of printable UHPFRC and UHPFRRuC. This study explores the development of 3D-printable UHPFRRuC, which overcomes the strength limitations of conventional rubberised concrete while retaining its superior impact resistance and damping properties. By integrating 3D printability, high strength, and enhanced energy absorption, UHPFRRuC presents significant potential for applications in resilient infrastructure, such as roadside barriers, earthquake-resistant slabs, and bridge components, warranting further investigation.