Complex Concrete Elements for the Production of Recyclable Formwork by Extrusion and Milling (2023-12)¶

The paper presents an additive process for the sustainable production of a recyclable formwork system based on concrete extrusion and milling, which allows the resource-efficient production of complex precast concrete parts. Within the framework of research work, concrete formulations were developed and characterized, which are produced close to the final contour by means of extrusion and then brought into the final form by means of high-precision machining. The resulting mould is used for the production of precast concrete parts. In order to increase the complexity of the components while further saving material, a forced mixing nozzle was designed which allows admixtures to be added shortly before the concrete is extruded. The integration of a concrete setting accelerator allows the production of higher overhangs of the components. The faster solidification of the concrete also reduces the printing time and the amount of material required, because the higher stability eliminates the need for individual support structures. After use as formwork, the recycling process continues, and the recycled material will be added back to the printing process. The development of the new near-net-shape technology is key for the success of efficient sustainable production of concrete components.