Page 69 - Demo

CONCRETE PRODUCTS & CAST STONEwww.cpi-worldwide.com CPI %u2013 Concrete Plant International %u2013 4 | 2025 69Figure 5 analyses the compressive strength of mixes with 35 wt.-% cement substitution, based on the content of CEM I 52.5 N. Mixes with tailings material (HM) were compared to two reference materials: pulverized coal fly ash (SFA) with a specific surface area of 3,600 cm%u00b2/g and limestone powder (KSM) with 6,300 cm%u00b2/g. Strength tests were conducted after 28 and 56 days.The results show that the mixes containing tailings material exhibited lower compressive strength values compared to the CEM I reference mix and the mix with SFA as a cement substitute, the latter being known for its pozzolanic reactivity. In direct comparison with limestone powder, an inert filler, the tailings material showed higher strength development, which could indicate a limited but existing microstructural contribution during the hardening process.The results confirm that, compared to an active pozzolanic additive, the tailings material does not represent an equivalent cement substitute, but it can be more effective than a purely inert material.The use of tailings material as aggregate replacement in concreteFigure 6 shows the processed tailings material after classification: on the left, the fine-grained material with a particle size of 0-2 mm, and on the right, the coarser material with a particle size of 2-8 mm. Both fractions were obtained by mechanical sieving. They correspond to the particle sizes commonly used as aggregates in concrete and could therefore potentially replace natural aggregate in paving block mix compositions. 62,7 56,344,035,965,5 69,451,942,401020304050607080CEM SFA HM KSMCompressive strength (MPa)28 days 56 daysFig. 5: Comparison of compressive strength values, pozzolanic and inert materials.sales@penta-automazioni.it PRODUCT PRODUCTION IONHANDL HANDLING INGSECONDARY TREATMENTS SECONDARY TREATMENTS