The construction industry faces various challenges, e.g. reducing its carbon footprint and the extensive use of materials. Therefore, Computational Design and Additive Manufacturing gain more importance throughout the industry. In combination, they offer the possibility of manufacturing individually designed building components, which can be less material-consuming and structurally improved. The presented research displays and discusses the effect of force-flow-oriented reinforcement design in concrete beams concerning the flexural strength and the required amount of steel. For this purpose, different reinforcement layouts were designed and integrated into conventionally cast and additively manufactured beam components. For the design of the force-flow-oriented reinforcement layouts, a digital workflow is established, and FEM simulations are utilised. The load-bearing capacity of the beams is compared based on four-point bending tests. Due to the optimised reinforcement layout, an increase of flexural strength of more than 60% was achieved while keeping the reinforcement amount constant. It is also shown that using force-flow-oriented reinforcement layouts can save nearly 60% of the reinforcement needed to achieve the same flexural strength as a beam with a conventional reinforcement cage. Finally, the potential for automated force-flow-oriented reinforcement integration within additively manufactured components is discussed.

Die Stahlbetonbauweise wurde in ihren Anfängen mit ingeniösen, materialsparenden Konstruktionen verbunden, entworfen aus dem Verständnis des kongenialen Zusammenwirkens der beiden Werkstoffe Beton und Stahl. Heutzutage ist Stahlbeton das am meisten eingesetzte Material im Bauwesen. Durch den Einsatz von Systemschalungen und einfach zu verlegenden Flächenbewehrungen werden Baukonstruktionen gefördert, die in Bezug auf Lohnkosten optimiert sind, aber oftmals eine ineffiziente Materialausnutzung aufweisen. Stefan Polónyi hat in diesem Zusammenhang immer wieder das mangelnde Verständnis der Ingenieure für das Zusammenwirken von Beton und Bewehrung kritisiert. Mit dem Beton‐3D‐Druck steht eine digitale Fertigungstechnologie bereit, die eine neue Gestaltungsfreiheit im Betonbau ermöglicht bei gleichzeitig ressourceneffizientem Materialeinsatz. Für die Integration der Bewehrung besteht die Chance für eine kraftflussgesteuerte Führung in den zugbeanspruchten Bereichen. Dies erfordert neue Strategien für die kombinierte Additive Fertigung von Beton und Bewehrung.

The ingenious bridge, hall 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 widley 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 an inefficient use of material. In this context, Stefan Polonyi has repeatedly criticised 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 while at the same time making resource-efficient use of materials. 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.

Shotcrete 3D Printing (SC3DP) is a novel robot-guided AM technology developed at Technische Universität Braunschweig in the environment of the Digital Building Fabrication Laboratory (DBFL). For successful automation, it is crucial to understand and redefine the entire concrete spraying process with all its interdependent parameters. This paper presents the basic principles of the SC3DP technology together with the results of a comparative study on the influence of the two concrete printing techniques extrusion and SC3DP on the interlayer bond strength. In particular, the effect of different time intervals between the deposition of two adjacent layers regarding mechanical properties (bond strength) is investigated. As will be shown, the SC3DP method allows convenient mechanical properties although the printed samples exhibit distinct anisotropies. The reasons are discussed based on investigations of the air void distribution by micro CT and mechanical test results.

AbstractThe 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.

Additive manufacturing in construction: first 3-D-printed reinforced concrete components using Shotcrete 3-D Printing (SC3DP) technology 3-D printing (additive manufacturing) is a digitally controlled manufacturing technology, that has the potential to be specifically developed for the construction industry and to become a key technology for the digitalization in building industry. In additive manufacturing (AM), the component construction is done solely by a digitally controlled layer-by-layer material application, without mold construction or forming processes. This represents a paradigm shift to the still predominantly manual shaping construction processes. In order to fully exploit the potential of AM structural design, material behavior and manufacturing processes must be integratively aligned. This enables buildings with a high degree of design freedom and resource-efficient use of materials. At the Institute of Structural Design (ITE) and at the Institute of Building Materials, Concrete Construction and Fire Safety (iBMB) at the Technische Universitat Braunschweig, research has been carried out for several years into processes for the 3-D printing of large-format concrete components. The so-called Shotcrete 3-D Printing (SC3DP) technology was developed in an interdisciplinary research project. The SC3DP technology is an automated robotic, additive manufacturing process that builds up concrete components layer by layer with the controlled addition of compressed air. This report presents the first 3-D-printed and reinforced concrete components that demonstrate the potential of SC3DP.

This paper presents the general aim of the research at the Institute of Structural Design (ITE) at Braunschweig University of Technology to bring digital design and digital fabrication together to develop resource efficient construction elements, manufacturing processes and building systems. Basis of research at ITE is the so-called Digital Building Fabrication Laboratory (DBFL). The paper gives an overview of machine design, the technical parameters and its basic abilities of subtractive and additive processes e.g. milling, printing and scanning. Based on the combined use of these digital fabrication processes and in cooperation with highperformance materials such as ultra-high performance concrete (UHPC), different research projects are being performed at the ITE. To explain the possibilities of the DBFL, the paper will present the results of two different – additive and subtractive research projects to develop fabrication techniques for the building industry. The first project is dealing with the development of “digitally fabricated high precision Non-WasteWax-Formwork for innovative UHPC structures” and the second project is investigating “Additive manufacturing of free-form concrete elements using Shotcrete 3D Printing (SC3DP) technology”. Finally, the paper will highlight the possibilities of combining these technologies and transferring them