Printability and Strength of 3D-Printed Concrete (2025-09)¶

This study investigates the properties of 3D printed concrete mixtures, focusing on rheological characteristics, compressive strength, anisotropy, and printing path effects. Two mixtures were compared: M-1 (90% cement, 10% metakaolin) and M-2 (85% cement, 10% metakaolin, 5% silica fume). M-2 demonstrated superior performance in flowability, shape retention, and buildability, allowing for 164% more printed layers than M-1. Compressive strength tests revealed that 3D-printed specimens consistently exhibited lower strength compared to cast specimens due to layering effects and anisotropy. M-2 showed higher compressive strength in both cast and printed cubes. Significant anisotropy was observed in mechanical properties, with compressive strength highest in the X direction and lowest in the Y direction. Flexural strength and elastic modulus also varied depending on the loading direction. Among printing patterns, the zigzag pattern with 90-degree rotation between layers (P1) exhibited the highest compressive strength, while circular patterns (P2) showed the lowest. These findings emphasize the importance of optimizing