Interlayer bonding performance of 3D printed engineered cementitious composites (ECC): Rheological regulation and fiber hybridization

The weak interlayer adhesion caused by the layer-by-layer 3D printing (3DP) process and the incorporation of organic fiber in Engineered Cementitious Composites (ECC), detrimentally impacts the integrity of 3DP-ECC structures, particularly for large-scale structures requiring extended open time. To optimize the printing quality and extent the operation time, cellulose filaments (CF) were employed as nano-reinforcement, viscosity modifier and water retainer, and were hybridized with polyethylene fiber (PE) and steel fiber (ST). The highest bonding strength was raised up to 3.51 MPa. The time-dependent escalation of rheological parameters was mitigated, reducing interlayer porosity to 0.56 % and limiting the reduction in bonding strength to 12.01 % within 60 min open time. The compressive anisotropy was almost eliminated, verifying the potential of CF in modifying interlayer adhesion. A linear correlation between rheological behavior and interlayer bonding performance was established, and a 0.508 Pa s/min plastic viscosity growth rate was suggested to avoid cold joint and ensure printing quality.