Exploring Interfaces in 3D-Printed Concrete Through Cohesive Zone Modelling (2025-10)¶

3D Concrete Printing (3DCP) is a revolutionary construction technology in which concrete is deposited layer-by-layer from a nozzle mounted on a gantry or a robotic arm. The absence of formwork in this innovative technique enhances cost-effectiveness, accelerates the construction process, and offers a more sustainable alternative than conventional methods. Although knowledge concerning 3DCP is progressing, certain technical challenges need to be addressed for the industry to grow. One primary concern is the presence of interfaces between stacked layers of concrete that can induce anisotropy in the mechanical properties of 3D-printed components and affect their performance. Another critical issue is the absence of established experimental protocols and design standards for designers to follow. This study focuses on the finite element analysis of the interlayers within 3D-printed concrete as a dependable finite element model can offer valuable insights in-to the delamination of interfaces and expedite the process of establishing codified standards. 3D-printed concrete specimens subjected to uniaxial tension and compression were simulated in Abaqus, and then their results were compared to corresponding experimental tests. The interfaces were modelled using two different methods based on the cohesive zone modelling (CZM) approach. These methods include cohesive elements and cohesive surface contact. In each case, the constitutive relation of the interface was defined by the traction-separation law. The findings showed that cohesive elements provided more precise results in direct tension regarding the tensile strength and load-displacement response compared to a surface-based cohesive interaction. However, for specimens under compression, neither cohesive elements nor cohesive surface contact effectively captured interface failure despite demonstrating a reduction in compressive strength in 3D-printed concrete compared to mould-cast concrete. Moreover, the study explored the impact of interface stiffness and damage evolution parameters on the overall response of specimens with zero-thickness cohesive elements. It was concluded that the strength of the interface is not significantly affected by its stiffness if the latter exceeds the modulus of elasticity of the concrete material within the layer. Additionally, it was observed that a linear softening behaviour in damage evolution better conformed to the load-displacement curve of specimens subjected to tension.