Research Summary Report of A05

TU Braunschweig, Institute of Mechanics and Adaptronics (IMA)

The individual integration of fibre reinforcement into large additively manufactured concrete components allows new design freedom and reduces concrete consumption due to reduced concrete cover. Strategies for the integration of freely formable reinforcing strands for different AM processes are being developed in project A05. A Dynamic Winding Machine is used to prepare reinforcement strands. This machine is used to consolidate and impregnate a primary fibre strand and wind a secondary yarn around it as a surface structuring. Thus, these reinforcement strands can be adapted for different purposes and enable more efficient production of highly customised, reinforced concrete elements.

Summary

Within WG Hühne (A05), reinforcement structures are produced for integration into large additively manufactured components. A custom-built Dynamic Winding Machine (DWM) enables adaptive, on-demand production of fiber reinforcement strands. In cooperation with WG Hack, a holistic approach is pursued to produce structural components directly on-site by combining additive manufacturing with innovative reinforcement strategies: Core Winding, Frame Winding, and Pin-grid Winding.
Three demonstrators have been realised to date: Shelltonics (see Fig. 1), the Knitcrete bridge, and a Pavilion-element as a large-scale Frame Winding demonstrator. In the latter, a frame serves as the base for winding reinforcement to create thin-shell concrete elements, illustrating the versatility of the method. Sections from this demonstrator were cut out for detailed mechanical testing.

In addition to demonstrating the integration of fibre reinforcements in large-scale components, comprehensive tests were conducted to assess durability and mechanical performance. Most recently, these investigations focused on simulating two critical conditions: exposure to an alkaline environment and the impact of the Shotcrete 3D printing (SC3DP) process. For both scenarios, tensile tests were used to evaluate the tensile strength of the reinforcement strands. Shotcrete simulations, performed with varying supports and prestressing, showed no significant reduction in tensile capacity. In contrast, alkaline exposure led to a pronounced loss in strength, underlining the importance of material selection and protective measures.

A decision-support framework was developed from the fabrication and evaluation of demonstrators to guide the selection of reinforcement integration strategies for additively manufactured concrete structures. It compares methods by functional capabilities, applicability, and limitations, enabling the most appropriate choice for specific design and production needs.
Investigations were conducted on the sustainability of glass fibre composite reinforcements. In cooperation with C09, a Life Cycle Assessment (LCA) was performed to evaluate the entire production chain of the composites.
For comparison and evaluation of the ecological potential of the winded reinforcement strands, basalt composites were also produced as shown in Fig. 2, allowing a direct assessment of differences in environmental footprint. The tensile strength of the basalt rebars was tested and evaluated following ASTM D7205/D7205M-21. On average, the basalt rebars exhibited more than 35% higher tensile strength.