1. Red mud as geotechnical compositePrimož Pavšič, Marija Đurić, Mateja Košir, Primož Oprčkal, Vesna Zalar Serjun, 2025, objavljeni znanstveni prispevek na konferenci Povzetek: Red mud (RM), a by-product of the Bayer process, is produced in large quantities worldwide. It is mainly disposed of in settling ponds or through dry stacking, both of which pose environmental risks due to instability, alkaline emissions, and leaching of potentially toxic elements (PTEs). Several efforts have been made to utilize RM as an additive in soil remediation or in the production of construction materials. However, due to its fine-grained texture, poor mechanical properties, and tendency to leach harmful substances, RM alone is unsuitable for direct use in construction. Nevertheless, its mechanical properties and workability can be significantly improved by mixing it with hydraulic or pozzolanic binders, such as calcareous ashes.
In the present study the use of calcareous paper mill ash (PA) as an additive to RM, for production of geotechnical RM/PA composite was studied. The results demonstrate that mixing RM slurry with PA produces a soil-like geotechnical composite with suitable workability and mechanical properties for use in earthworks, comparable tonatural soils. Moreover, the RM/PA composite exhibits lower leaching of PTEs, in comparison to the RM, improvingthe environmental acceptability of RM for its use in construction.
This study confirms that RM composites, with addition of alternative binders, can be a viable construction material, which not only meet the geotechnical performance requirements for earthworks but also comply with Slovenian environmental standards. This approach offers a dual benefit: it reduces the environmental and economical burden associated with RM disposal while simultaneously decreasing the demand for natural construction materials.
Objavljeno v DiRROS: 06.02.2026; Ogledov: 654; Prenosov: 284
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2. Hydration and carbonation behaviour of selected recycled materials from SloveniaVesna Zalar Serjun, Primož Oprčkal, Anton Meden, Marta Počkaj, Romana Cerc Korošec, 2025, objavljeni znanstveni prispevek na konferenci Povzetek: The European Union’s shift towards a circular economy emphasizes the substitution of virgin materials with recycled alternatives, particularly in the construction sector, which can accommodate large volumes of industrial by-products. Ashes from coal, biomass, paper sludge, and co-combustion processes are abundant secondary materials whose variable chemical and mineralogical compositions necessitate careful assessment to enable safe and effective reuse.This study investigates the hydration behaviour and early carbonation potential of ashes of different origin. The ashes were characterized using X-ray fluorescence, X-ray diffraction, and scanning electron microscopy coupled with energy-dispersive spectroscopy. Hydraulic reactivity was evaluated by preparing ash pastes at a 1:1 water-to-ash ratio and monitoring hydration product formation over time using XRD. Carbonation of co-combustion ash was studied under controlled CO₂ conditions (2 % CO₂, 50 % RH, 20 °C ± 1 °C) at different moisture contents (0 wt.%, 10 wt.%, 20 wt.%, and 40 wt.%) and early curing times (0 hours, 1 hours, 4 hours, and 24 hours).Results indicate distinct differences among the ashes. Paper sludge ash exhibited the most extensive formation of calcium aluminate hydrates, coal and co-combustion ashes showed moderate hydration, while biomass ash produced only minor secondary phases. Carbonation of co-combustion ash proceeded concurrently with hydration, with lime depletion and calcite formation enhanced by higher moisture and longer curing. These coupled processes influenced both the kinetics and composition of hydration products. The findings demonstrate the potential of diverse combustion ashes for valorisation in construction materials and provide insight into their reactivity under early-age hydration and carbonation conditions, supporting circular economy initiatives.
Ključne besede: circular economy, ashes from combustion, hydraulic activity, carbonation, phase composition, amorphous phase
Objavljeno v DiRROS: 14.01.2026; Ogledov: 417; Prenosov: 263
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3. Eco-friendly bioleaching : innovative technology for extracting critical raw materials from WEEDragica Marinič, Miha Štruc, Primož Oprčkal, 2025, objavljeni znanstveni prispevek na konferenci Povzetek: The rapid growth of the quantity of generated electronic waste (ewaste), driven by the increasing demand for electrical and electronic equipment (EEE), has raised urgent concerns regarding its environmental and health impacts. E-waste is the fastes tgrowing global waste stream, with only a small fraction recycled sustainably. Printed circuit boards (PCBs), a major component of e-waste, contain valuable metals and hazardous substances, complicating recycling efforts. This study explores bioleaching as an environmentally friendly alternative to traditional recycling methods. Bioleaching, utilising microorganisms such as Acidithiobacillus ferrooxidans and A. thiooxidans, which can effectively extracts metals like copper, nickel, and zinc from e-waste, reducing environmental contamination. Our research, conducted under the EIT RawMaterials WEEE-NET9 project, focuses on bioleaching's potential for sustainable recovery of critical raw materials (CRMs) from e-waste. Results demonstrate the effectiveness of bioleaching in metal extraction, supporting the EU's goals of increasing CRM recycling and reducing reliance on primary sources for critical materials, which we have to import into the EU.
Ključne besede: e-waste, critical raw materials, circular economy, bioleaching, EIT RawMaterials WEEE-NET9 project
Objavljeno v DiRROS: 16.07.2025; Ogledov: 1020; Prenosov: 444
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4. Recycled red mud as an useful geotechnical materialPrimož Pavšič, Marija Đurić, Mateja Košir, Alenka Mauko Pranjić, Ana Mladenovič, Primož Oprčkal, Sara Seršen, Vesna Zalar Serjun, 2024, objavljeni znanstveni prispevek na konferenci Povzetek: Red mud (RM) is an extractive waste from Bayer process in alumina production. The most conventional methods of RM disposal are tailing dams, or dry storage,both of which raiseenvironmental concerns due to the high alkalinity of RMandthe presence and leaching of potentially hazardous elements (PTEs).Due to its fine-grained nature and poor mechanical properties, as well as leaching of potentially hazardous substances, RM cannot be used by itself. Properties of the RM can be improved, by mixing it with hydraulic or pozzolanic binders, such as calcareous ashes or steelmaking slag, to produce mechanically stable and durable composites for earthworks. On the other hand, RMcan also serve as an immobilization additive for remediation of contaminated soils.Two different approaches for useful utilization of RMare presented based on results of laboratory research and a real case study, opening of new possibilities for conserving natural resources and reducing environmental hazards of RM deposits.
Ključne besede: red mud, recycling, geotechnical composites, environment
Objavljeno v DiRROS: 30.10.2024; Ogledov: 1318; Prenosov: 1393
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5. Izgradnja lizimetrov za preučevanje izpiranja potencionalno nevarnih snovi iz gradbenih proizvodovJanez Turk, Janko Urbanc, Ana Mladenovič, Alenka Sešek Pavlin, Primož Oprčkal, Karmen Fifer Bizjak, Barbara Likar, Marko Brodnik, Nina Mali, 2020, izvirni znanstveni članek Povzetek: Z uporabo recikliranih odpadkov v gradbeništvu nadomeščamo naravne materiale in s tem vzpostavljamo krožno gospodarstvo na lokalnem nivoju. Pomemben vidik je tudi ohranjanje naravnih virov. To je še posebno pereče pri zemeljskih delih (npr. zasipih in nasipih), kjer prihaja do velike porabe materialov. Geotehnični kompoziti iz recikliranih materialov, v primerjavi z naravnimi agregati ali zemljinami, lahko vsebujejo višje celotne koncentracije potencialno nevarnih snovi (težke kovine, klorid, sulfat, fluorid, organska onesnaževala itd.). Pogoj za uporabo takšnih kompozitov je, da so v njih potencialno nevarne snovi imobilizirane in da so zato iz kemijskega vidika trajno inertni. Možni vplivi na okolje, predvsem prenos različnih potencialno nevarnih snovi iz kompozitov v tla oziroma vodonosnik, so običajno ovrednoteni na laboratorijski ravni, medtem ko je njihovo obnašanje v dejanskem okolju slabo proučeno. Zato se pojavljajo zahteve po razvoju občutljivih, zanesljivih in cenovno ter časovno učinkovitih orodij za določitev masnih tokov potencialno nevarnih snovi iz gradbenih proizvodov, na primer geotehničnih kompozitov, pod vplivi različnih okoljskih dejavnikov. V članku predstavljamo postopek vzpostavitve terenskega laboratorija na osnovi sistema "pan" lizimetrov, za zbiranje izcednih voda iz zasipov, ki so bili izdelani iz geotehničnih kompozitov iz recikliranih materialov. Lizimetre smo konstruirali in izvedli tako, da je njihova izgradnja cenovno ugodna, hkrati pa so po svojih dimenzijah dovolj veliki, da reprezentativno odražajo procese v zgrajenih geotehničnih zasipih. Pridobljeni podatki o količini in parametrih izcedne vode bodo služili kot osnova za določanje vodne bilance in za študij imobilizacije potencialno nevarnih snovi v kompozitih. Hkrati bodo uporabljeni kot vhodni podatki za geokemijski numerični model, s katerim bomo simulirali transport potencialno nevarnih snovi, sproščenih iz preučevanih kompozitov, v različnih tipih vodonosnikov (npr. medzrnski in razpoklinski).
Ključne besede: lizimeter, izlužek, okoljski monitoring, geotehnični zasip, odpadki
Objavljeno v DiRROS: 12.09.2023; Ogledov: 3297; Prenosov: 1063
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6. Remediation of contaminated soil by red mud and paper ashPrimož Oprčkal, Ana Mladenovič, Nina Zupančič, Janez Ščančar, Radmila Milačič Ščančar, Vesna Zalar Serjun, 2020, izvirni znanstveni članek Povzetek: Remediation of contaminated soil can be performed by using various techniques, which must be adequately tailored for each specific case. The aim of this research is to critically evaluate the potential use of red mud and paper ash and a combination of the two as immobilization additives for the remediation of contaminated soil from one of the most polluted sites in Slovenia. The proposed procedure involves the preparation of geotechnical composites made from contaminated soil and mixed with 25 wt% of immobilization additives and an optimal quantity of water to achieve consistency, at which maximum compaction according to the Proctor Compaction Test procedure can be achieved. The results reveal a positive, time-dependent trend for the immobilization of potentially toxic elements in the composite with paper ash, because of the formation of the new hydration products with potentially toxic elements. In a composite containing only red mud, potentially toxic elements were immobilized by sorption mechanisms with no general time-dependent trends. The composite with a combination of additives demonstrates the remediation characteristics of both red mud and paper ash. Using this approach excavated contaminated soil, red mud and paper ash can be successfully recycled in the proposed composites, which can be beneficially used in situ for rehabilitation of contaminated sites. Nevertheless, mobilization of some potentially toxic elements at high pHs may represent a limiting factor and has to be taken into the consideration when a combination of red mud and paper ash is used as immobilization additive.
Ključne besede: red mud, paper ash, contaminated soil, potentially toxic elements, geotechnical composites
Objavljeno v DiRROS: 31.08.2023; Ogledov: 2575; Prenosov: 1631
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7. Environmental impacts and immobilization mechanisms of cadmium, lead and zinc in geotechnical composites made from contaminated soil and paper-ashMarija Đurić, Primož Oprčkal, Vesna Zalar Serjun, Alenka Mauko Pranjić, Janez Ščančar, Radmila Milačič Ščančar, Ana Mladenovič, 2021, izvirni znanstveni članek Povzetek: Paper-ash is used for remediation of heavily contaminated soils with metals, but remediation efficiency after longer periods has not been reported. To gain insights into the mechanisms of immobilization of cadmium (Cd), lead (Pb), and znic (Zn), a study was performed in the laboratory experiment in uncontaminated, artificially contaminated, and remediated soils, and these soils treated with sulfate, to mimic conditions in contaminated soil from zinc smelter site. Remediation was performed by mixing contaminated soil with paper-ash to immobilize Cd, Pb, and Zn in the geotechnical composite. Partitioning of Cd, Pb, and Zn was studied over one year in seven-time intervals applying the sequential extraction procedure and complementary X-ray diffraction analyses. This methodological approach enabled us to follow the redistribution of Cd, Pb, and Zn over time, thus, to studying immobilization mechanisms and assessing the remediation efficiency and stability of newly formed mineral phases. Cd, Pb, and Zn were effectively immobilized by precipitation of insoluble hydroxides after the addition of paper-ash and by the carbonization process in insoluble carbonate minerals. After remediation, Cd, Pb, and Zn concentrations in the water-soluble fraction were well below the limiting values for inertness: Cd by 100 times, Pb by 125 times, and Zn by 10 times. Sulfate treatment did not influence the remediation efficiency. Experimental data confirmed the high remediation efficiency and stability of insoluble Cd, Pb, and Zn mineral phases in geotechnical composites.
Ključne besede: cadmium, lead, zinc, contaminated soil, paper ash, immobilization mechanisms
Objavljeno v DiRROS: 04.07.2023; Ogledov: 2508; Prenosov: 1413
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8. Environmental acceptability of geotechnical composites from recycled materials : comparative study of laboratory and field investigationsMarija Đurić, Vesna Zalar Serjun, Ana Mladenovič, Alenka Mauko Pranjić, Radmila Milačič Ščančar, Janez Ščančar, Janko Urbanc, Nina Mali, Alenka Sešek Pavlin, Janez Turk, Primož Oprčkal, 2023, izvirni znanstveni članek Povzetek: The environmental properties of three geotechnical composites made by recycling wastes were investigated on a laboratory scale and in the field with the use of lysimeters designated for the revitalization of degraded mining sites. Composites were prepared by combining the mine waste with paper-mill sludge and foundry sand (Composite 1), with digestate from municipal waste and paper ash (Composite 2), and with coal ash, foundry slag and waste incineration bottom ash (Composite 3). The results of laboratory leaching tests proved that Composites 1 and 3 are envi- ronmentally acceptable, according to the legislative limits, as the potentially hazardous substances were immobilized, while in Composite 2, the legislative limits were exceeded. In the field lysimeters, the lowest rate of leaching was determined for optimally compacted Composites 1 and 3, while for Composite 2 the leaching of Cu was high. This study proved that optimally installed Composites 1 and 3 are environmentally acceptable for use in construction as an alternative to virgin materials, for the revitalization of degraded mining sites or, along with Composite 2, for closure operations with landfills. In this way, locally available waste streams are valorised and channelized into a beneficial and sustainable recycling practice.
Ključne besede: waste, recycling, lysimeter, potentiali hazardous substances, immobilization, revitalisation, environmental, open access
Objavljeno v DiRROS: 29.05.2023; Ogledov: 1693; Prenosov: 1417
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9. A glimpse of the lost Upper Triassic to Middle Jurassic architecture of the Dinaric Carbonate Platform margin and slopeBoštjan Rožič, Luka Gale, Primož Oprčkal, Astrid Švara, Tomislav Popit, Lara Kunst, Dragica Turnšek, Tea Kolar-Jurkovšek, Andrej Šmuc, Aljaž Iveković, Jan Udovč, David Gerčar, 2022, izvirni znanstveni članek Povzetek: In the southernmost outcrops of the Slovenian Basin the Middle Jurassic coarse-grained limestone breccia (mega)beds are interstratified within a succession that is otherwise dominated by hemipelagites and distal turbidites. In this paper, these beds are described as the Ponikve Breccia Member of the Tolmin Formation. We provide descriptions of the studied sections with detailed geological maps and analysis of the breccia lithoclasts. From the latter, a non-outcropping margin of the Dinaric Carbonate Platform is reconstructed. In the Late Triassic the platform margin was characterized by a Dachstein-type marginal reef. After the end-Triassic extinction event, the platform architecture remained, but the reefs were replaced by sand shoals characterized by ooids. In the late Early Jurassic and/or early Middle Jurassic a slope area might have been dissected by normal faults and a step-like paleotopography was formed. In the Bajocian, during a period of major regional geodynamic perturbations, extensional or transtensional tectonic activity intensified and triggered the large-scale collapses of the Dinaric Carbonate Platform margin producing the limestone breccias described herein. This may in turn have caused a backstepping of the platform margin, as is evident from the occurrence of Late Jurassic marginal reefs that are installed directly above the Upper Triassic and Lower Jurassic inner platform successions.
Ključne besede: Slovenian Basin, Dinaric Carbonate Platform, Middle Jurassic, limestone breccia, debris-flow, stratigraphy, Ponikve breccia
Objavljeno v DiRROS: 18.01.2023; Ogledov: 2000; Prenosov: 1228
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10. Dokaz za norijsko-retijsko natezno tektoniko v Slovenskem bazenu (Južne Alpe)Primož Oprčkal, Luka Gale, Tea Kolar-Jurkovšek, Boštjan Rožič, 2012, izvirni znanstveni članek Ključne besede: baški dolomit, sinsedimentni prelom, tektonika, trias, zgornji, Slovenski bazen, Južne Alpe
Objavljeno v DiRROS: 05.02.2016; Ogledov: 6025; Prenosov: 0 |
