Interlocking 3D Printed Concrete Filaments Through Surface Topology Modifications for Improved Tensile Bond Strength (2022-06)¶

Numerous organizations in the additive concrete manufacturing industry generally observe weak bonding between deposited filaments in 3D concrete printing. The consequences thereof are far reaching, including significant anisotropic mechanical behaviour as well as impaired durability. Several attempts have been made to address this issue, for example via chemical modification of the interlayer and repair mortar inclusion. However, limited literature exists on physical alteration of the interlayer toward enhanced filament bonding. This paper attempts to employ a biomimicry principle, namely topological interlocking, in order to facilitate filament bonding. This is achieved by exploiting the enhanced mechanical resistance provided in shear compared to tension loading only. Three simple geometrical patterns, namely square, sinusoidal and zigzag are selected to incorporate a combination of tension and shear resistance at the interlayer region. The direct tensile test (DTT) is used to experimentally evaluate the bond strength improvement capability of each pattern while maintaining a constant groove frequency, amplitude and width throughout the experiment. All three patterns indicate a noticeable improvement over the conventional horizontal interlayer with the square pattern achieving the highest followed by the sinusoidal pattern and lastly the zigzag pattern. Practical implications relating to the implementation of topological interlocking are discussed, and recommendations provided for further research into this novel application.