Abstract
Recently, 3D concrete printing has progressed rapidly in the construction industry. However, this technique still contains several factors that influence the buildability and mechanical properties of the printed concrete. Therefore, this study investigated the effects of the nozzle speed, the interlayer interval time, the rotations per minute (RPMs) of the screw in the 3D printing device, and the presence of lateral supports on the buildability of 3D concrete printing. In addition, this paper presents the results of the mechanical properties, including the compressive, splitting tensile, and flexural tensile strengths of 3D printed concrete. The buildability of 3D printed structures was improved with an extended interlayer interval time of up to 300 s. The printing processes were interrupted because of tearing of concrete filaments, which was related to excessive RPMs of the mixing screw. The test results also showed that a lateral support with a wide contact surface could improve the resistance to buckling failure for 3D printed structures. The test results of the mechanical properties of the 3D printed concrete specimens indicated that the compressive, splitting tensile, and flexural tensile strengths significantly depended on the bonding behavior at the interlayers of the printed specimens. In addition, although metal laths were expected to improve the tensile strength of the printed specimens, they adversely affected the tensile performance due to weak bonding between the reinforcements and concrete filaments.
Highlights
The 3D printing technique has become promising for prefabricated structures because of its outstanding flexibility in both architectural and structural designs [1]
This study focused on the effect of the printing parameters and structural stability parameter on the buildability of 3D printed concrete
This study originally focused on the experimental program and discussion of the test results in terms of buildability
Summary
The 3D printing technique has become promising for prefabricated structures because of its outstanding flexibility in both architectural and structural designs [1]. The printing performance is strongly dependent on the fresh properties of concrete, such as its rheology and green strength [13,14,15], and the printing parameters, such as the nozzle speed, nozzle height, interlayer interval time, and extrusion rate [16,17,18,19]. These factors influence the mechanical properties of 3D printed concrete in the hardened state. It is important to investigate the buildability for the printing of concrete structures and the mechanical properties of hardened concrete
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