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www.cpi-worldwide.com CPI %u2013 Concrete Plant International %u2013 5 | 2025Materials and methodsMaterial development, analyses and recyclingThe aim was to develop a material with low CO2emissions from the raw materials used. The focus was also on low abrasiveness for tool-friendly processing and cost-effective components. The recycling process is based on a turbulent air flow within the grinding zone of a turbo rotor. Within the micro-vortex, two or more particles are crushed by colliding with each other. The particles remain suspended in the air during the entire process. The starting material is usually fed into the mill after pre-crushing. The mill is designed for continuous grinding operation. During operation, no dust can escape from the mill as it is constantly pressurised. Extrusion and processing technologyThe fully automated extrusion process was carried out in collaboration with the robot complex [5] developed in the Department of Lightweight Construction at the Technical University of Chemnitz, as shown in Fig. 1. The Robo-Arena consists of two KUKA 6-axis industrial robots, a screw pump extruder for conveying the concrete and specially developed nozzles, e.g. for forced mixing of additions fed to the nozzle or a nozzle for combined injection/extrusion technology [5,6]. The second robot can be used, for example, for inserting reinforcements or processing concrete.Various tools were used to process the fresh concrete. In this study, for example, a solid carbide end mill and brushes with different degrees of hardness were used (see Fig. 2).The cured milling tests were carried out using a 5-axis portal milling machine. The use of absolute servo motors means that no referencing of the machine is required. Solid carbide ball nose end mills, roughing cutters, finishing cutters and milling heads with diamond inserts were used.Fig. 1: Robo-Arena for fully automatic extrusion and processing [2, 3]