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Earth sciences support society by finding suitable deposits of primary raw materials, while material sciences support production of new and advanced environmental and health-friendly materials that we all use for everyday activities [...].

The bottleneck in the process for increasing production of low CO2 mineral binders, based on BCSA (belite sulfoaluminate) clinkers, is the availability of Al-rich raw materials. For that purpose, a new registry of Al-containing secondary mineral residues (industrial and mine waste) has been developed and is presented in this paper. The methodology of creating the registry consists of three main steps: Gathering ideas, consolidation of ideas, and implementation. In order to achieve this, the following methodology was adopted: Analysis of similar registries by potential end-users and seeking potential solutions and tools to be used, and conducting 3 rounds of stakeholder consultations via workshops in order to determine crucial parameters and features the registry needs to contain. The key discussion points were about which data the registry needs to contain, who shall be the potential users, and what are the stakeholder’s expectations from the registry’s portal. Potential individual registry variables were identified as being relevant/irrelevant or available/unavailable, and potential solutions for the registry’s sustainability were explored. Each Al-rich waste/residue data entry is divided into 10 slots, describing legal status, location, quantities, chemical (REE included), mineralogical, physical and radiological properties, life-cycle assessment, additional data, and data relevancy. The registry will act as a matchmaking tool between producers/holders of Al-rich secondary raw materials and potential producers of cement clinkers.

Resuspended street dust is a source of inhalable particles in urban environments. Despite contaminated street dust being a possible health risk factor for local population, little is known about the contribution of atmospheric dust emissions and other factors to the content of toxic metals in street dust. The impact of smelting, traffic, and power plants on metal contaminates in street dust is the focus of street dust sampling at 46 locations in the Witbank area (Republic of South Africa). This area is characterized by numerous open-pit coal mines in the Karoo coal basin, which provides a cheap source of energy to numerous metallurgical smelters and ironworks and supplies coal to the coal-fired power plants located nearby. Street dust was collected on asphalt or concrete surfaces with hard plastic brushes, avoiding collecting of possible sand, soil, or plant particles. Chemical analysis was done on the <0.125 mm fraction using inductively coupled plasma mass spectrometry subsequent to total digestion. Exceptionally high concentrations of metals were detected with concentrations of Fe reaching 17.7 %, Cr 4.3 %, Mn 2 %, Ni 366 mg/kg, and V 4,410 mg/kg. Factor analysis indicates three sources for the pollution. Road traffic which contributes to the high concentrations of Cu, Pb, Sb, and Sn, with the highest impacts detected in the town of Witbank. The second source is associated with the metal smelting industry, contributing to Fe, Co, Mn, and V emissions. The highest factor scores were observed around four metallurgical smelter operations, located in the Ferrobank, Highveld, and Clewer industrial areas. Impact of vanadium smelter to street dust composition could still be detected some 20 km away from the sources. Exceptionally high concentrations of Cr were observed in four samples collected next to the Ferrobank industrial area, despite Cr not being loaded in factor 2. The last source of the pollution is most probably fly ash associated with the coal-fired power plants and fly ash dumps. Elements which are associated with this source are Al, Sr, and Li. This factor is abundant in the coal mining part of the study area.

PurposeAlkali activation process has been applied to fresh river clay-rich sediments in order to increase their mechanical properties and make them suitable for soil stabilization.Materials and methodsDredged sediments were mixed with up to 30 mass percent (ma%) of fly ash (FA) or ladle slag (LS) and after curing for 3 days at 60 °C, the bending and compressive strength have been determined. The mixtures which exhibited the highest strengths were further optimized for being used in soil stabilization. For this purpose, the sediment was stabilized with 4 ma% of quicklime (QL) and after 1 h 30 ma% of FA with alkali activator was added and cured for 1, 7 and 28 days.ResultsThe stabilized sediment has a significantely better geomechanical performance in comparison with the sediment alone. Stabilizing the dredged sediment using alkali activation technology provides high enough strengths to eventually make it suitable for anti-flood embankments.ConclusionsThe results confirmed the suitability of the investigated technology for soil stabilization.

The late Eocene to Recent dynamics of the NW External Dinarides in Slovenia are described. The study is focused on the orogen-parallel NW-SE striking family of faults, which represent the main source of seismic hazard in the NW External Dinarides today. Approximately 1700 fault- slip datasets were collected at 70 locations and used for palaeostress analysis. Structural relationships observed in the field, allowed the construction of a relative chronology between the documented fault and shear joint sets, facilitating the reconstruction of their kinematic evolution and the chronology of palaeostress phases. Four post-Palaeocene stress tensor groups are documented corresponding to four distinct tectonic phases. The first phase is marked by NE-SW directed compression attributed to Late Eocene top-to-SW thrusting of External Dinarides. The second phase is characterized by NE-SW oriented tension, documented by normal slips recorded on NW-SE striking faults. This tension is interpreted as an expression of the Early to Middle Miocene back-arc extension in the Pannonian basin system that also affected the studied part of the External Dinarides. The third phase is manifested by approximately E-W oriented compression with approximately N-S oriented tension in a strike-slip stress regime, causing sinistral reactivation of NW-SE trending faults. Geodynamically, this phase can be correlated with the Late Miocene short pulse of E-W directed compression, documented in parts of the Pannonian basin system. The youngest phase is characterized by approximately N-S oriented compression and approximately E-W oriented tension in a strike-slip stress regime, which caused dextral reactivation of NW-SE striking faults. This phase correlates with the recent inversive/transpressive phase, well-established from seismological data.

Lower Cretaceous syn-orogenic sediments derived from the obducted ophiolites of the Meliata–Maliac–Vardar (Neotethys) Ocean are typically found in the Dinarides and the Austroalpine units. Correlative flysch-type deposits linking both regions through the Southern Alps had been reported from the Bohinj area (NW Slovenia), but their stratigraphic and structural framework remained poorly known. Our research focused on stratigraphic and structural field studies in a 50 km 2 area between Lake Bled and Lake Bohinj in the Julian Alps. The mixed carbonate–siliciclastic sediments, informally named the Studor formation, range in age from the Valanginian (possibly late Berriasian) to the Aptian. They occur on top of two different stratigraphic successions, which we assign to two separate nappes. The first succession consists of deep-water Middle Triassic to Lower Cretaceous deposits of the Bled Basin and belongs to the Pokljuka Nappe, which is the uppermost nappe of the Julian nappe stack. The second succession consists of Upper Triassic to Lower Jurassic platform carbonates and a thin Jurassic–Cretaceous deep-water sequence. This succession was deposited in the marginal area of the Julian Carbonate Platform/Julian High and now belongs to the underlying Krn Nappe. The original (Dinaric) thrust contacts between the Pokljuka and Krn nappes are obliterated by younger deformations. The present-day boundaries between these two nappes are steep NE–SW and younger NW–SE trending faults. The post-nappe deformation sequence characterizing the Alps–Dinarides transition zone has been recognized: (1) Oligocene–Early Miocene NW–SE contraction; (2) Early–Middle Miocene extension; and (3) Late Miocene to recent inversion and transpression.

The potential use of steel slag from treated steel slag in belite-sulfoaluminate cements was investigated in this study. Cement clinkers with two phase compositions were synthesized, allowing the incorporation of different amounts of steel slag. The phase composition and microstructure of cement clinkers at three different sintering temperatures were studied by X-ray powder diffraction and the Rietveld method, as well as scanning electron microscopy with energy dispersive spectrometry. The results showed that the targeted phase composition of clinkers was achieved at a sintering temperature of 1250 °C. However, a higher amount of perovskite instead of ferrite was detected in the clinker with a higher content of Ti-bearing bauxite. Apart from the main phases, such as belite, calcium sulfoaluminate, and ferrite, several minor phases were identified, including mayenite, perovskite, periclase, and alkali sulfates. In both clinker mixtures, a higher content of MgO in the steel slags resulted in the formation of periclase. Furthermore, the hydration kinetics and compressive strength at 7 and 28 days were studied in two cements prepared from clinkers sintered at 1250 °C. As evidenced by the results of isothermal calorimetry, the hydration kinetics were also influenced by the minor clinker phases. Cement with a higher content of calcium sulfoaluminate phase developed a higher compressive strength.

This study investigated the influence of different cooling regimes on the microstructure and consequent reactivity of belite-sulfoaluminate clinkers. The cement clinkers were synthesized by incorporating secondary raw materials, such as titanogypsum and bottom ash, to the natural raw materials. Clinker phases were determined by Rietveld quantitative phase analysis, while the distribution morphology and the incorporation of substitute ions in the phases were characterized by scanning electron microscopy using energy-dispersive X-ray spectroscopy (SEM/EDS). Clinker reactivity was studied using isothermal calorimetry and was additionally investigated through compressive strength, which was determined for the cement prepared from the synthesized clinkers. X-ray diffraction analysis showed that, as well as the three main phases (belite, calcium sulfoaluminate, and ferrite), the clinkers contained additional minor phases (mayenite, gehlenite, arkanite, periclase, and perovskite), the ratios of which varied according to the cooling regime utilized. Microscopic observations indicated that the cooling regime also influenced the crystal size and morphology of the main phases, which consequently affected clinker reactivity. Furthermore, a smaller amount of substitute elements was incorporated in the main phases when cooling was slowed. Results showed that, in comparison to clinkers cooled at slower rates, air quenched clinkers reacted faster and exhibited a higher compressive strength at 7 days.

The late Eocene to Recent dynamics of the NW External Dinarides in Slovenia are described. The study is focused on the orogen-parallel NW-SE striking family of faults, which represent the main source of seismic hazard in the NW External Dinarides today. Approximately 1700 fault-slip datasets were collected at 70 locations and used for palaeostress analysis. Structural relationships observed in the field, allowed the construction of a relative chronology between the documented fault and shear joint sets, facilitating the reconstruction of their kinematic evolution and the chronology of palaeostress phases. Four post-Palaeocene stress tensor groups are documented corresponding to four distinct tectonic phases. The first phase is marked by NE-SW directed compression attributed to Late Eocene top-to-SW thrusting of External Dinarides. The second phase is characterized by NE-SW oriented tension, documented by normal slips recorded on NW-SE striking faults. This tension is interpreted as an expression of the Early to Middle Miocene back-arc extension in the Pannonian basin system that also affected the studied part of the External Dinarides. The third phase is manifested by approximately E-W oriented compression with approximately N-S oriented tension in a strike-slip stress regime, causing sinistral reactivation of NW-SE trending faults. Geodynamically, this phase can be correlated with the Late Miocene short pulse of E-W directed compression, documented in parts of the Pannonian basin system. The youngest phase is characterized by approximately N-S oriented compression and approximately E-W oriented tension in a strike-slip stress regime, which caused dextral reactivation of NW-SE striking faults. This phase correlates with the recent inversive/transpressive phase, well-established from seismological data.

The increase in industrial waste generation presents a global problem that is a consequence of the needs of modern society. To achieve the goals of the EU Green Deal and to promote the concept of circular economy (CE), the valorization of industrial residues as secondary raw materials offers a pathway to economic, environmental, energetic, and social sustainability. In this respect, Al-containing industrial residues from alumina processing (red mud), thermal power plants (fly ash and bottom ash), and metallurgy (slag), as well as other industries, present a valuable mineral resource which can be considered as secondary raw materials (SRMs) with the potential to be used in construction, supporting the concept of circular economy. This paper focuses on the characterization of 19 secondary raw materials from the East South-East Europe (ESEE) region regarding their physical, chemical, mineralogical, and radiological characteristics. The goal is to provide a foundation for future innovations based on secondary raw materials, in alignment with the EU Green Deal and the principles of circular economy. The results showed that fly ash has the potential to be the best material among those analyzed to be used in the cement industry, mainly due to its favorable radiological and mineralogical properties. However, it is important to control the amount of free lime in the mixture, ensuring it remains below 10%. After evaluating secondary mineral raw materials for metal recovery, the results indicate that these materials are not viable sources for base metals or other technology-critical metals, such as REEs.