## 3 Additive Manufacturing of Reinforced Concrete Process (AMoRC)
### Development of the AMoRC Process  
In the following, the conceptual design of a novel 3D printing process for reinforced concrete, the so-called Additive Manufacturing of Reinforced Concrete (AMoRC), is presented. The proposed process is visualized in Figure 2. The process uses a combined print head, which allows for formwork-free depositing of concrete layers and uses a welding unit for simultaneous production of reinforcement. Here, the welding unit runs ahead of the concrete extrusion process and produces the spatial reinforcement mesh from prefabricated reinforcing bar segments. The concrete is placed around the reinforcing bars in such a way that they protrude a few centimeters from the printed concrete. The end zones of reinforcement bars sticking out of the concrete body can be used for joining/attaching a next row of bar segments in subsequent layers of the printing process. In this way, it is possible to create two- or three-dimensional reinforcement meshes, bridging interfaces between subsequent layers of concrete and to simultaneously encase them with concrete. The result of combining the \begin{table}
\begin{tabular}{c c c} \hline \hline
**Dimension** & & **Requirement/Target** \\ \hline Process engineering & \(\bullet\) & Printing of RC by use of a combined print head for steel and concrete or with separate but simultaneously operating print heads for steel and concrete \\  & \(\bullet\) & Unify/synchronize the feed rates of reinforcement mesh production and concrete extrusion \\  & \(\bullet\) & Use of cost-effective, widely available, and comprehensively researched components (concrete and reinforcing steel) \\  & \(\bullet\) & Large-scale feasibility for construction sites/ precast concrete plants \\ \hline Structural behavior & \(\bullet\) & Continuity of reinforcement across printed concrete interfaces \\  & \(\bullet\) & Low energy input during welding of reinforcement in order to minimize thermal impairment of metallic materials \\  & \(\bullet\) & Ensuring sufficient bond between reinforcement and concrete \\  & \(\bullet\) & Adapting reinforcement layout to internal flow of forces e.g., through variability of used reinforcement diameters \\ \hline Durability & \(\bullet\) & Sufficient concrete cover and avoidance of defects to ensure protection of reinforcement against corrosion \\ \hline Economic efficiency & \(\bullet\) & Use of cost-effective and widely available building materials (concrete and reinforcing steel) in order to use existing supply chains in the construction industry and reduce the cost of R\&D \\ • & \(\bullet\) & Low energy consumption (e.g., no shape welding) \\ • & \(\bullet\) & Minimal material input (e.g., through economically designed, force flow-adapted reinforcement mesh) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Requirements for a viable 3D printing process for reinforced concrete. intermittent welding production process and the continuous concrete extrusion process is AMoRC, a hybrid production process for RC structures. In contrast to processes that use shape welding for incremental built up of rebars [23; 27], the reinforcement mesh in the AMoRC process is joined from segmented rebars of limited length (Figure 2). The length of the bar segments is adapted to the desired concrete layer thickness and concrete extrusion speed and is usually between 10 and 100 cm. The joining of prefabricated bar segments drastically reduces the time required to produce the reinforcement compared to shape welding. Furthermore, significantly less energy is consumed and the lower heat accumulation results in significantly better material properties of the reinforcing steel. The welding processes used to join the prefabricated bar segments are either stud welding (enables straight joining of bars) (Figure 2), MAG welding (enables straight joints but also a deflection of bars) or a combination of both methods. The bar segments to be joined are kept ready in a magazine belonging to the print head (not shown in Figure 2), which enables the feeding of bars with different diameters.