A Study into the Effect of Material-Deposition-Methods on Hardened Properties of 3D Printed Concrete (2023-03)¶

Concrete 3D printing (3DCP) is a novel construction method that uses the principle of additive manufacturing (AM) to build the concrete structure in a layered fashion directly from 3D computer aided digital model. Out of several AM techniques, extrusion-based 3D printing was widely used for AM of concrete structures. However, unlike the metal and polymer, concrete structures are expected to be high rise, hence the use of pumping of concrete is needed to avoid manual material loading in a typical screw driven extruder. This paper investigates the effects of these two material deposition methods such as direct pumping and screw based extrusion on hardened properties of the printed structures. From the experimental results, it was found that the maximum strength of the pumped specimens was around 68 MPa in 28 days which is close to casted strength (72 MPa). Even the pumped specimens gave higher mechanical strength with lesser anisotropic variation compared to the extruded specimens, irrespective of the change in layer height. The maximum compressive strength of the printed specimens decreased from 30% to 10% as layer height increased (from 10 mm to 15 mm) for extruded and pumped specimens, respectively. The cross sectional view of the printed specimens was used to compute the percentage of porosity, which was then connected with the percentage of layer overlap of the ideal mathematical sketches. These results are further backed with bond strength data which indicates 22 % higher inter layer and 33 % higher intra layer bond strength of the pumped specimens when compared to the extruded specimens of 10 mm layer height print.