The adaptation of 3D printing techniques within the construction industry has opened new possibilities for designing and constructing cementitious materials efficiently and flexibly. The layered nature of extrusion-based concrete printing introduces challenges, such as interlayer weaknesses, that compromise structural integrity and mechanical performance. This experimental study investigates the influence of interlayer orientation and the presence of cold joints (CJ) on mechanical properties, such as stiffness and strength. Three-point bending tests (3PBT) and optical measurement techniques are employed to correlate these properties with the structural response of hardened printed concrete. The analysis determines key properties like Young’s modulus and flexural tensile strength and evaluates them statistically. The investigation examines crack development and failure mechanisms, relating them to the material properties. The findings reveal a strong dependency of material properties and crack formation on layer orientation. Specimens with interlayers aligned parallel to the loading direction exhibit significantly inferior mechanical properties compared with other orientations. The presence of CJ considerably influences the progression of crack formation. This research contributes to a deeper understanding of the structural performance of printed concrete.

Extrusion-based printing of cementitious materials represents an innovative technology in civil engineering. The additive manufacturing process significantly influences the material properties in the hardened state, leading to anisotropic behaviour in terms of stiffness and strength compared to conventionally cast concrete. This experimental study aims to deepen the understanding of the mechanical behaviour of hardened printed concrete. Beam-like specimens with varying printing patterns, loading orientations and lengths are investigated within three-point bending tests (3PBT) and uniaxial compression tests (UCT). Homogenized material parameters such as Young’s modulus, compressive and flexural tensile strength and density are statistically evaluated using optically measured displacement and strain fields on the specimen surface. The qualitative and quantitative results demonstrate a strong dependency of material properties and failure mechanisms on the printing pattern. The interfilamental and interlayer areas with weak adhesion are identified as the main reason for anisotropy.