Research Summary Report of A04

[21.03.2023]

Robin Dörrie; phd candidate, r.doerrie@tu-braunschweig.de,

Technische Universität Braunschweig, Institute of Structural Design

Main goal

Within this project, basic research on various Shotcrete 3D Printing (SC3DP) strategies, materials, tools and methods will be conducted with regard to enhanced material and process control, reinforcement integration, surface quality and automation. To that end, different reinforcement materials in combination with suitable reinforcement manufacturing and integration concepts will be investigated based on force-flow oriented reinforcement alignment. Besides, design strategies as well as material and process control will be researched in detail. Furthermore, tools and strategies for precise control of the surface quality and geometric resolution of SC3DP elements are subject of research.

Summary

Currently TP A04, closely together with TP A05, is working on finalising a demonstrator to show the potential of the SC3DP technology and the investigated reinforcement integration methods during funding period one. Taking on the challenge of large scale, in this case manufacturing the proposed final demonstrator (see Fig. 1), many new research questions and challenges occurred. These range from developing new printing strategies for complex geometries to controlling the robotic movement to reach a high precision during printing.As reinforcement integration is a current challenge in concrete 3D printing, A04 investigated several integration methods and materials during the manufacturing of the final demonstrator. A combination of Short Rebar Insertion (SRI) and Interlayer Reinforcement (ILR) was used to create continuous 3D reinforcement structures within the element (see Fig. 2). Also a combination of SRI and Fibre Winding (FW) was integrated as a combined reinforcement structure.

Furthermore the integration of functional elements, like heating wire, pipes, electrical wires or ventilation was successful during the printing. This shows the robustness of the process as well as the progress of the online control process developed by B04.In addition post-processing strategies for surface finishing were utilised during the manufacturing of the final demonstrator as part of the A04 research. Ongoing experiments showed the advantages and challenges of using traditional surface finishing tools and the opportunity to investigate new end effectors for complex geometries (see Fig. 3).

Current state of research

Current research focuses on the three main topics: reinforcement integration methods, printing strategies and the processing of surfaces. In the field of reinforcement integration the combination of processes is investigated since the manufacturing of a three dimensional and continuous structure is of utmost important in the design of force-flow oriented reinforcement layouts. In particular a focus is set on the integration of short rebars and the overlapping of rebars, regarding the precision of automated integration and the individual bonding of the rebars.

To manufacture large scale concrete elements certain parameters have to be considered: 1. the material behaviour, 2. the geometric complexity and resulting path planning and 3. parallel processes e.g. reinforcement integration. Due to the large impact of these parameters on the course of the process, an exact orchestration of steps and machines is necessary. This will be systematically investigated by A04 to provide fundamental strategies for the printing of large scale construction elements. Furthermore the surface quality is being investigated by A04. Due to the direct integration of reinforcement into the construction element, the is the opportunity for process parallel surface finishing to reach the near net shape geometry as design without applying more material as an external cover layer. For this process also new tools and path strategies are being investigated.