Additive manufacturing (AM) in industrial applications benefits from increasing interest due to its automation potential and its flexibility in manufacturing complex structures. The construction and architecture sector sees the potential of AM especially in the free form design of steel components, such as force flow optimized nodes or bionic-inspired spaceframes. Robot-guided wire and arc additive manufacturing (WAAM) is capable of combining a high degree of automation and geometric freedom with high process efficiency. The build-up strategy (layer by layer) and the corresponding heat input influence the mechanical properties of the WAAM products. This study investigates the WAAM process by welding a bar regarding the build-up geometry, surface topography, and material properties. For tensile testing, an advanced testing procedure is applied to determine the strain fields and mechanical properties of the bars on the component and material scale.

The ingenious bridge, roof, and shell structures of the last century were designed from the understanding of the congenial interaction of the two materials concrete and steel. Nowadays, reinforced concrete is the most widely used material in construction. The use of system formwork and easy‐to‐install reinforcement support structures that are optimized in terms of labor costs, but often have inefficient use of material. In this context, Stefan Polónyi has repeatedly criticized the engineers' lost understanding of the interaction of concrete and reinforcement. With Additive Manufacturing, an innovative digital manufacturing technology is now available that allows new freedom in concrete design with a resource‐efficient use of materials at the same time. With regard to practical application, the integration of reinforcement represents a central challenge in 3D‐concrete‐printing. The authors see here the future chance of a force‐flow controlled reinforcement layout. The paper shows new strategies for the combined Additive Manufacturing of concrete and reinforcement and presents first 3D‐printed reinforced concrete elements.

Today, the majority of research in 3D concrete printing focuses on one of the three methods: firstly, material extrusion; secondly, particle-bed binding; and thirdly, material jetting. Common to all these technologies is that the material is applied in horizontal layers. In this paper, a novel 3D concrete printing technology is presented which challenges this principle: the so-called Injection 3D Concrete Printing (I3DCP) technology is based on the concept that a fluid material (M1) is robotically injected into a material (M2) with specific rheological properties, causing material M1 to maintain a stable position within material M2. Different to the layered deposition of horizontal strands, intricate concrete structures can be created through printing spatially free trajectories, that are unconstrained by gravitational forces during printing. In this paper, three versions of this method were investigated, described, and evaluated for their potential in construction: A) injecting a fine grain concrete into a non-hardening suspension; B) injecting a non-hardening suspension into a fine grain concrete; and C) injecting a fine grain concrete with specific properties into a fine grain concrete with different properties. In an interdisciplinary research approach, various material combinations were developed and validated through physical experiments. For each of the three versions, first architectural applications were developed and functional prototypes were fabricated. These initial results confirmed both the technological and economic feasibility of the I3DCP process, and demonstrate the potential to further expand the scope of this novel technology.