###### Abstract  
Reinforced concrete (RC) is by far the most widely used composite material in the world. Despite the enormous economic importance of RC construction, there is a lack of viable concepts for its digital fabrication. While 3D printing of plain concrete has been pushed forward by a growing research community in recent years, methods for integration of steel reinforcement have only scarcely been researched and little attention has been payed to meet the practical requirements of construction sites and prefabrication plants. Therefore, full-scale implementations of current approaches are hardly available. Based on both, a sound review of R&D for digital fabrication of RC structures and an analysis of practical requirements, the present paper proposes a novel 3D printing process for RC structures, called Additive Manufacturing of Reinforced Concrete (AMoRC), viable for real-world application. In this hybrid process, consisting of an intermittent stud welding process and a continuous concrete extrusion process, segmented steel reinforcing bars are joined to form a three-dimensional reinforcement mesh and simultaneously encased with extruded concrete. The paper describes the conceptual design and development of the process and demonstrates the results of preliminary investigations on its feasibility. As AMoRC enables the operation of rebar welding and concrete extrusion process with synchronized feed rates, combination of both processes in one hybrid print head for digital fabrication of RC is a key-advantage of the proposed method. Keywords:digital fabrication with concrete; 3D printing; integration of reinforcement; AM; stud welding; extrusion of concrete +
Footnote †: journal: Applied  
layer, which hardens during the printing process. In addition to processes based on material extrusion, there is a large variety of other additive manufacturing processes like layer laminated manufacturing or powder bed fusion. An overview is presented in [3]. In many branches of industry, the workpieces to be printed are small components made of polymers, steel or ceramics, which in terms of size are significantly smaller than the dimensions commonly used in the construction industry. However, since the mid-1990s AM has also been gradually entering the construction sector. [PERSON] presented the Contour Crafting (CC) system [4], which was the first implementation of an additive manufacturing process for cement-based materials. As the name Contour Crafting suggests, only the outer contour of a component is printed, while the inner cavity is filled with self-compacting concrete. Conventional formwork can be avoided by this method. A short time later, Loughborough University developed another extrusion-based process called Concrete Printing, which is capable of producing not only the outer contour but entire structures by means of additive production [5; 6]. Under the influence of this pioneering work, numerous universities and companies have started to develop 3D printing technologies for concrete. Today, research into the additive manufacturing of concrete is the subject of a rapidly growing global research community. Most research work to date is centered around the specific adjustment of fresh concrete properties to make concrete printable (e.g., rheological properties for pumping and depositing of concrete). An overview on research activities in this field can be found in [7; 8]. In recent years, various technologies for 3D printing of plain concrete have been developed, mainly based on the principle of extrusion of fresh concrete. At the same time, the number of demonstration projects and prototypical applications of printed concrete has increased considerably. In Europe, the work of [PERSON] (TU Dresden) [9; 10], [PERSON] (University of Ghent) [11; 12] and [PERSON] (Eindhoven University of Technology) [13; 14] is particularly noteworthy.