Anisotropy of 3D Printed Concrete Strength and Elasticity for a Well-Developed One-Component and Two-Component Concrete Mixture (2026-03)¶

With the rise of more established printing methods and materials in the field of 3D concrete printing, the structural application of printed elements is no longer a distant future thought. While executed projects are now mainly based on the principle of ‘design by testing’, there is an urgent need for a thorough understanding of the mechanical behavior of 3D printed concrete (3DPC), in order to develop and rely upon representable numerical models. This work presents an in-depth investigation into the often-mentioned anisotropic nature of extrusion-based 3DPC, owing to its layer-wise buildup. Based on an experimental campaign, finding its inspiration in rock mechanics, the hypothesis of transverse anisotropy for 3DPC is investigated. The study includes a one-component and a two-component concrete mixture designed for use for structural applications, printed with the same laboratory setup, and draws conclusions both for the compressive strength as well as the compressive elastic behavior. The results show no clear anisotropic behavior for the one-component and two-component mixture if samples are continuously printed with zero time-gap. However, important differences are observed between cast and printed samples, showing reduced stiffness and strength for printed elements of the one-component mixture. Verification through an isotropic approach seems to capture the compressive behavior well. The mechanical results are supported by investigations into the micro- and macroporosity through mercury intrusion porosimetry and X-ray computed tomography scanning, explaining the differences in strength and stiffness through the presence of large capillary pores and a larger overall macroporosity.