Page 65 - Demo

CONCRETE PRODUCTS & CAST STONEwww.cpi-worldwide.com CPI %u2013 Concrete Plant International %u2013 4 | 2025about the suitability of tailings. To assess potential environmental hazards, the \tion of Waste According to Its Hazardous Nature\by the German Environment Agency must be consulted.Physical, chemical, and mineralogical characterization of tailings to assess their suitability as a secondary raw materialThe raw tailings material shows an extremely coarse particle size distribution, with a median value (x50) of 390 %u00b5m and an upper percentile (x90) of 1,397 %u00b5m. The Blaine-specific surface area in this state is only 2,350 cm%u00b2/g, indicating very low fineness and therefore limited reactivity. Due to its coarse grain structure and low specific surface area, the unground material is considered inactive and is unsuitable as a reactive cement substitute.After targeted grinding, the particle size distribution was significantly shifted into the reactive range. The ground material now exhibits a median (x50) of 19 %u00b5m and an x90 of 69 %u00b5m (see Fig. 1, left). As a result, a significant portion of the particles falls within the typical range for hydraulically or pozzolanically active additives, i.e. 10-50 %u00b5m. For sufficient reactivity, particle sizes below 63 %u00b5m, ideally below 45 %u00b5m, are generally targeted %u2013 criteria that are largely met here.n Ferdinand Senf completed his Bachelor%u2019s degree in Civil Engineering at the University of Applied Science in Nuremberg from 2017 to 2021. As part of a dual study program, he also worked at STRABAG AG in Nuremberg, where he completed his training as a road construction worker and later worked as a construction manager. From 2021 to 2023, he pursued a Master%u2019s degree in Lightweight Construction at Chemnitz University of Technology. During this time, he was employed as a technical assistant in the division of Structural Lightweight Construction and Plastics Processing in the research area of lightweight construction in civil engineering, where he has been working as a research associate since 2023. Since 2024, he has also been a research associate at the Steinbeis Innovation Center FiberCrete in Chemnitz. His research focuses on clinker-reduced concretes and their application in additive manufacturing through 3D printing. ferdinand.senf@mb.tu-chemnitz.den Henrik Funke studied Ceramics, Glass, and Construction Materials Engineering at the Technical University Bergakademie Freiberg from 2004 to 2009 and has been a research associate at Chemnitz University of Technology since 2010. Since 2013, he has also served as Head of Research and Development at the Steinbeis Innovation Center FiberCrete in Chemnitz. His work focuses on fiber-reinforced mineral-based construction materials. His ongoing research covers both cement-based and cement-free materials (e.g., alkali-activated binders). henrik.funke@mb.tu-chemnitz.den Prof. Dr.-Ing. habil. Sandra Gelbrich has been the head of the Department of Lightweight Construction in Civil Engineering at the Institute of Structural Lightweight Engineering at Chemnitz University of Technology since 2009. She received her doctorate in 2009 and completed her habilitation between 2012 and 2016 on the topic %u201cFunctionally Integrated Lightweight Structures for Load-Bearing Systems in Civil Engineering.%u201d In 2012, she founded the Steinbeis Innovation Center FiberCrete in Chemnitz.sandra.gelbrich@mb.tu-chemnitz.de