Towards rebar-free 3D printed high-strength engineered cementitious composites construction: Rheology characterization, material and structural element performances

The application of engineered cementitious composite (ECC) in 3D concrete printing has the potential to achieve rebar-free 3D concrete printing. To improve the strength of 3D printed ECC, this study utilized polyethylene (PE) fibers to regulate the rheological and mechanical properties of the material, thereby developing a 3D printable high-strength ECC (3DP-HSECC) and systematically investigated the rheological properties, mechanical characteristics and flexural behaviors of the 3DP-HSECC. The addition of PE fiber increases the viscosity- enhancement effect of fibers on the matrix, and thus achieves favorable printability and shape-retention capability. The results reveal that the compressive strength of 3DP-HSECC exhibits anisotropy, which is influenced by fiber orientation and interface properties of 3DP-HSECC. The highest compressive strength is observed when specimens are loaded perpendicular to the interface, demonstrating 21.3% and 78.1% increases compared to mold-cast specimens and printed specimens loaded parallel to the interface, respectively. The 3DP-HSECC beams show coordinated deformation under flexural loading with no significant horizontal interlayer slippage. Numerical simulations of 3DP-HSECC under compression and flexure demonstrate well agreement with experimental result. Parametric analysis indicates that an interlayer bond strength exceeding 3.0 MPa has the minimal influence on the flexural performance of printed 3DP-HSECC beams. The findings provide a design foundation for the application and promotion of 3DP-HSECC.