3D printing concrete structures: State of the art, challenges, and opportunities

3D printing concrete technology is an integration of material preparation, geometric modeling, structural design, and construction with the essential advantages of green, low-carbon, and intelligent construction, which had a booming development in recent years. Due to the specificity of printing materials and printing technology, 3D printing concrete exhibits unique macroscopic anisotropy, and the research on the constitutive relation of 3D printing concrete is still insufficient. Although there are numerous engineering cases of 3D printing concrete, mature structural reinforcement enhancement methods as well as quantitative structural bearing capacity analysis theories and methods are still needed to be studied. To adapt to the specific requirements of materials and printing processes, and achieve the efficient usage of materials, the optimal design is essential for 3D printing concrete structures. The field of optimal design of 3D printing concrete is currently in its infancy. Finally, the printing, connection, and construction methods of the slab, shell, beam, and arch structures provide a multifaceted reference for 3D printing concrete structures. In general, the selection of 3D printing concrete materials and structures as well as the design and construction of structures are problematic. Based on the above-mentioned, this paper reviews four aspects which include mechanical properties of materials, structural forms, optimal design, and connection construction methods in the context of engineering examples.