Examining the Significance of Infill-Printing-Pattern on the Anisotropy of 3D Printed Concrete (2020-09)¶

Additive manufacturing relies on the deposition of layers of material upon existing ones. The nature of this method disadvantages materials such as concrete due to the rheological changes of the material over time, the lack of standardization of the printing process, and the nature of the deposition process. This paper examines the significance of infill printing patterns on the anisotropic properties of3D printed concrete. The rheological properties, the compressive strength, and the interlayer and interfilamentous bond strength of the 3D printed concrete were characterized. We show that there is a directional dependency on all the infill patterns. The specimens show lower compressive strength, and modulus of elasticity in the Z (extrusion) direction compared with the X and Y directions but insignificant difference of the strength and modulus between the X and Y directions. However, no directional dependency was found for the strain at failure. On the other hand, no significant difference in the mechanical properties of 3D printed concrete was observed or can be attributed to the infill printing patterns. The results also show that the 3D printed concrete shows higher compressive strength, for two out of the three testing directions (X and Y) than conventionally cast concrete. This is due to the compactness associated with the printing process that is strongly dependent on the printing parameters.