Effect of Coarse Aggregate and Steel Fiber Interaction under Extrusion on the Performance of 3D-Printed Steel Fiber-Reinforced Concrete (2026-01)¶

Incorporating coarse aggregate and fibers into 3D-printed concrete can enhance its strength and toughness while reducing cement consumption and carbon emissions. However, the incorporation of coarse aggregate affects the orientation and dispersion of fibers, and the interaction between the two also influences concrete’s overall performance. This study systematically investigated the effects of maximum coarse aggregate particle size (8∼15 mm) and volume fraction (0∼25%) on the mechanical properties and microstructure of 3D printed steel fiber reinforced concrete with coarse aggregate (3DP-FRC). Experimental results indicate that the incorporation of coarse aggregate reduces mechanical anisotropy, with the anisotropy coefficient decreasing from 0.328 to 0.143 as aggregate content increases from 0% to 25%. Both compressive strength and splitting tensile strength increase as the aggregate size and content increase, reaching up to 72.5 MPa and 2.46 MPa, respectively. However, the flexural strength and flexural toughness ratio decrease by up to 28.74% and 11.72%, respectively, attributed to geometric constraints imposed by coarse aggregates that reduce the fiber orientation coefficient and impaired dispersion homogeneity. Quantitative analysis via X-ray computed tomography (X-CT) reveals that the post-peak flexural toughness ratio is synergistically governed by fiber orientation and dispersion, showing a proportional increase with enhancements in orientation and dispersion coefficients. This study may serve as a reference for the application and optimization of 3DP-FRC in engineering practice.