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CONCRETE PRODUCTS & CAST STONE66 CPI %u2013 Concrete Plant International %u2013 4 | 2025 www.cpi-worldwide.comAfter grinding, the Blaine-specific surface area reached 4,000 cm%u00b2/g, indicating that the achieved particle size distribution may be related to potential reactivity. Against this background, chemical reactivity of the material appears fundamentally possible.The raw density of the material is 2.67 g/cm%u00b3, which lies within the typical range for silicate mineral mixtures. The mineralogical composition of the examined tailings material shows a high proportion of quartz (38.8 wt.-%) (see Fig. 1, right). Under normal conditions, quartz is chemically inert and does not contribute to pozzolanic or hydraulic reactions in cementitious systems.Another major component is muscovite (19.0 wt.-%), a mica mineral. Muscovite typically has low reactivity under standard conditions but features a distinct layered structure and specific surface area that, when finely ground, may promote pozzolanic behaviour. However, its actual reactivity potential strongly depends on the fineness and the degree of activation.Biotite, plagiograde, K-feldspar, and chlorite, which collectively form a significant portion of the material, belong to the group of primary silicate minerals. In their natural form, these exhibit low to moderate reactivity, which can be improved through thermal or mechanical activation. However, their potential remains limited compared to highly reactive secondary phases.Kaolinite, present in trace amounts (1.7 wt.-%), is a clay mineral phyllosilicate known for its high pozzolanic activity. However, due to its low concentration in this material, the contribution to the overall reactivity is considered negligible.The initial scanning electron microscope (SEM) images (Fig. 2) were taken using the coarse material, clearly demonstrating the necessity of fine grinding to optimize it for potential use Fig. 2: SEM images of the tailings material.Table 1: Results of the column percolation test according to DIN 19528:2023 (water/solid ratio = 2/1) with raw tailings material.Parameter Unit Result BM-F3pH-value %u2013 7.4 5.5-12.0Electrical conductivity %u00b5S/cm 276 2000Chloride mg/l < 4 %u2013DOC mg/l < 5 %u2013Chromium (total) %u00b5g/l < 3 600Fluoride mg/l 9.81 %u2013Copper %u00b5g/l 12 320Arsen %u00b5g/l 741 100Molybdenum %u00b5g/l 1286 %u2013