Effects of printing patterns and loading directions on fracture behavior of 3D printed Strain-Hardening Cementitious Composites

Strain-Hardening Cementitious Composites (SHCC) have gained widespread attention as self-reinforcing materials in 3D concrete printing. Meanwhile, owing to the layer-by-layer build-up process during extrusion-based 3D printing, interfaces have a significant impact on the fracture behavior of 3D printed concrete. In this study, 3D printed SHCC (3DP-SHCC) specimens were prepared with two printing patterns: parallel-printing and cross-printing. Cubic compressive strength tests and three-point bending tests of notched beams were conducted. The results showed that the compressive strength of 3DP-SHCC was 1.23 ∼ 1.45 times higher than that of mold-cast SHCC. Parallel-printed SHCC exhibited a significant degree of anisotropy. The initial and unstable fracture toughness (KICini, KICun), flexural strength (Ff), and fracture energy (Gf) of parallel-printed SHCC in the X direction were 1.31, 1.81, 1.39, and 1.79 times those of mold-cast SHCC, respectively. In comparison, the cross-printed SHCC showed significantly lower anisotropy in the X and Y directions. By incorporating cohesive elements with the cohesive damage plasticity model, the fracture behavior of the 3DP-SHCC could be accurately simulated.