Influence of the Nozzle Geometry on Mechanical Properties of 3D Printed Concrete (2024-12)¶

The rapid advancement of 3D printing technology has revolutionized the construction industry by offering capabilities such as printing complex structures, significant time and labour savings, and cost reductions. To comprehensively understand the mechanical behaviour of 3D-printed concrete structures, a combination of experimental testing and finite element (FE) modelling is imperative. This study investigates the strength characteristics of casted versus 3D-printed concrete structure, employing two different nozzle shapes (circular and square nozzle). Uniaxial compression and flexural test are conducted in the two principal material directions to assess structural performance. Finite element simulations, utilizing the cohesive zone model, are employed to simulate fracture behaviour, with the traction–separation law calibrated for two material directions. Results indicate that the strength of printed specimens is influenced by the material loading direction, with a significant effect from nozzle shape variation. The 3D printed exhibits better flexural performance for both nozzle forms as compared to the traditionally cast specimen. However, when it comes to uniaxial compression (UC) and the three-point bend (TPB) test, the specimen printed with the circular nozzle performs better than the square nozzle. The maximum flexural load for the circular and square nozzles are 135.6% and 110.4%, respectively, in comparison with traditionally cast specimen. Moreover, the load–displacement behaviour observed experimentally in the prism specimen is accurately predicted through FE studies. Understanding the propagation of cracks and the distribution of stress at the loading point region is also provided by FE investigation. This comparative analysis provides valuable insights into the mechanical performance of 3D-printed concrete structures, aiding in their further optimization and widespread adoption in the construction industry.