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CONCRETE PRODUCTS & CAST STONE72 CPI %u2013 Concrete Plant International %u2013 4 | 2025 www.cpi-worldwide.comFor the production of the paving blocks, a reference concrete mix was used, consisting of 1000 kg/m%u00b3 aggregate in the 0-2 mm size range, 1000 kg/m%u00b3 aggregate in the 2-8 mm size range, and 250 kg/m%u00b3 CEM III/A 52.5 L. The water/cement ratio was 0.5. The mix was classified as earth-moist, ensuring immediate shape stability after compaction.To determine consistency, the compaction degree was measured according to DIN EN 12350-4:2019. The measured compaction value of V = 1.38 classifies the mix in consistency class C1 (%u201cstiff%u201d). The produced concrete mix corresponds to the base layer in which coarse aggregate is used. In industrial applications, a fine-grained surface layer is typically applied on top of this layer for optical and functional enhancement.For the experimental investigation, a total of nine paving slabs measuring 300 mm %u00d7 300 mm with a thickness of 60 mm were produced. For this, 100 litres of fresh concrete were mixed, poured into prepared moulds, and compacted using a vibrating press (Fig. 7). Immediately afterward, the slabs were demoulded, realistically simulating an industrial manufacturing process. The demoulded slabs were then transferred to a temperature-controlled curing chamber for hardening.To demonstrate the laying quality and surface effect, the nine paving slabs were arranged after curing to form a 900 mm %u00d7 900 mm test paving area (Fig. 8 and 9).Summary and outlookThe results of the investigations show that the processed tailings material is fully suitable as an aggregate replacement in concrete mixes to produce the core concrete for paving blocks and paving slabs. In cooperation with the recomine-alliance, a project funded by the German Federal Ministry of Education and Research is looking into a process for the selective removal of arsenic contained in the material. Upon successful implementation of this technology, there is potential to establish the tailings material permanently as a resource-efficient building material due to its high availability and mineralogical suitability. This not only makes a significant contribution to the circular economy but also enables sustainable reuse of mining legacy sites in an ecologically and economically sensible manner. nReferences[1] VDZ (2021): Dekarbonisierung von Zement und Beton %u2013 Roadmap der deutschen Zementindustrie zur Klimaneutralit%u00e4t bis 2050. Verein Deutscher Zementwerke e.V., D%u00fcsseldorf.[2] Senf, F., Javed, R., Funke, H., & Gelbrich, S. (2024). Concrete Extrusion Using Sustainable Cement Alternatives. In International Scientific Conference Environmental Challenges in Civil Engineering (pp. 175-188). Cham: Springer Nature Switzerland. doi.org/10.1007/978-3-031-73776-3_12Fig. 9: Paving area 90 %u00d7 90 cm%u00b2.