1. Comparison of the mineralogy and microstructure of EAF stainless steel slags with reference to the cooling treatmentMojca Loncnar, Ana Mladenovič, Marija Zupančič, Peter Bukovec, 2017, izvirni znanstveni članek Povzetek: TIn the present study the differences in the mineralogical composition and microstructure of various types of EAF stainless steel (EAF S) slag with regard to the cooling treatment, the operation practice in an EAF (electric arc furnace) and environmental ageing reactions were evaluated. It was shown that the mineralogy of the investigated EAF S slags varied from one slag to another, depending on the quality of the produced stainless steel. The production process of the treated steel also has a strong influence on the mineralogy of the slags. The conditions during water cooling treatment were not sufficient to prevent the crystallization of primary mineral phases, which occurs predominantly in air-cooled EAF S slags, probably due to the high basicity of the investigated slags. However, the water cooling treatment of hot slag leads to the absence of γ-CaSiO 4 and the formation of secondary mineral phases predominantly calcite, portlandite, ettringite, calcium aluminate hydrate and calcium silicate hydrate. It has been shown that during the environmental ageing test (down-flow column test) secondary mineral phases were formed, which were the same as those formed during the water cooling treatment.
Ključne besede: electric arc furnace stainless steel slag, cooling path, microstructure, mineralogy
Objavljeno v DiRROS: 14.08.2024; Ogledov: 40; Prenosov: 68
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2. Characterization of bloom iron smelting site remains in Pržanj, SloveniaJaka Burja, Barbara Šetina, Daša Pavlovič, 2024, izvirni znanstveni članek Povzetek: This paper gives an overview of findings, connected with metallurgical activity, at the Pržanj archeological site near Ljubljana, Slovenia. More than 230 kg of slag and other remains connected with early medieval (from the 5th to the 12th century AD) metallurgical activities was found at the excavation site. The remains were grouped into four categories, i.e., furnace remains, ore, slag and a ferrous product, and analyzed in detail to obtain their chemical composition, microstructural characteristics, and mineral phase composition. The furnace wall remains, identified by their morphology and chemical composition, revealed an intensive iron processing activity at the site. The iron ore at the site was identified as goethite (FeO(OH)), a surprising find in Slovenia where limonite is typically used, and its presence suggests the potential exploitation of local bog iron ore, given the site’s geological context. Abundant slag remains at the site, identified by their shape, molten microstructure, and mineral components like wuestite, fayalite, and hercynite, indicated sophisticated smelting practices, including the use of CaO-rich materials to lower the melting temperature, a technique likely preserved from antiquity. Findings of ferrous products at ancient metallurgical sites are rare due to their value, but the discovery of a corroded iron bloom conglomerate at this site, initially mistaken for furnace remains, highlights the challenges in identifying small, corroded ferrous fragments that are often misidentified as ore. The results indicate extensive metallurgical activity at the excavation site, marking it as the first documented early medieval iron smelting production site in Slovenia.
Ključne besede: bloom iron, bloomery slag, archaeometallurgy, microstructure
Objavljeno v DiRROS: 29.07.2024; Ogledov: 129; Prenosov: 133
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3. Utilisation of reused steel and slag : analysing the circular economy benefits through three case studiesGenesis Camila Cervantes Puma, Adriana Salles, Janez Turk, Viorel Ungureanu, Luís Bragança, 2024, pregledni znanstveni članek Povzetek: This research explores sustainable construction practices focusing on material reuse, specifically reclaimed structural steel and slag. In general, the building stock is not designed for deconstruction, and material recovery for reuse at the end of life of buildings is complex and challenging. The study evaluates the benefits of content reuse through a thorough analysis of three case studies— BedZED eco-friendly housing, Angus Technopôle building, and the use of steel slag aggregate in road construction. It highlights the value of reclaimed structural steel and by-products like steel slag in waste reduction, energy conservation, and resource preservation. The BedZED case study showcases recycled steel’s cost-effectiveness and economic viability in construction, while the Angus Technopôle building exemplifies the adaptive reuse of an old steel frame building. Additionally, the third case study showcases the benefits of using Electric Arc Furnace C slag in asphalt-wearing courses, highlighting the reduction in greenhouse gas emissions and environmental impact. The versatility of reclaimed structural steel and slag is evident in integrating material reuse in building construction and road infrastructure. These case studies illustrate the potential for reusing steel and its by-products in various construction contexts, from eco-friendly housing to road development. Therefore, the study aims to demonstrate the feasibility and benefits of sustainable practices within the construction industry by showcasing the successful incorporation of reclaimed steel and slag in these projects. Considering the significant contributions of building construction to global greenhouse gas emissions, raw material extraction, and waste production, the study advocates for adopting circular economy (CE) principles within the construction industry. Finally, the analysis of case studies underscores the advantages of reclaimed structural steel and the valorisation of steel slag through the lens of CE and their contribution to sustainable development.
Ključne besede: circular economy, reused steel, steel slag aggregate, reclaimed steel, steel members
Objavljeno v DiRROS: 12.04.2024; Ogledov: 308; Prenosov: 141
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4. Particle size manipulation as an influential parameter in the development of mechanical properties in electric arc furnace slag-based AAMKatja Traven, Mark Češnovar, Vilma Ducman, 2019, izvirni znanstveni članek Povzetek: Alkali-activated materials (AAM) have gained recognition as a promising alternative to technical ceramic and building materials owing to the lower energy demands for production and the potential to use slag as a precursor. In the present study, five sets of slag-based AAM pastes were prepared with different particle sizes (fractions d < 63, 63 < d < 90, and 90 < d < 125 μm in different mass ratios) under the same curing regime and using a fixed precursor to activator (water) mass ratio. Precursors and the hardened AAM are evaluated using BET, XRD, XRF, SEM, FTIR, reactivity of precursors by leaching, and mercury intrusion porosimetry (MIP). Chemical analysis indicated only marginal differences among the different-sized fractions of input materials, whereas the BET surface area and reactivity among the precursors differed significantly-smaller particles had the largest surface area, and thus, higher reactivity. The mineralogical differences between the precursors and hardened AAM were negligible. The results revealed that compressive strength was significantly influenced by particle size, i.e., a threefold increase in strength when the particle size was halved. Microstructural evaluation using MIP confirmed that the porosity was the lowest in AAM with the smallest particle size. The low porosity and high reactivity of the fine fractions led to the highest compressive strength, confirming that manipulation of particle size can significantly influence the mechanical properties.
Ključne besede: alkalijsko aktivirani materiali, žlindra iz obločne peči, mehanska aktivacija, mehanske lastnosti, poroznost, alkali-activated materials (AAM), electric arc furnace steel slag, mechanical activation, mechanical properties, porosity
Objavljeno v DiRROS: 22.11.2023; Ogledov: 522; Prenosov: 224
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5. Impacts of casting scales and harsh conditions on the thermal, acoustic, and mechanical properties of indoor acoustic panels made with fiber-reinforced alkali-activated slag foam concretesMohammad Mastali, Paivo Kinnunen, Marjaana Karhu, Zahra Abdollahnejad, Lidija Korat, Vilma Ducman, Ahmad Alzaza, Mirja Illikainen, 2019, izvirni znanstveni članek Povzetek: This paper presents experimental results regarding the efficiency of using acoustic panels made with fiber-reinforced alkali-activated slag foam concrete containing lightweight recycled aggregates produced by using Petrit-T (tunnel kiln slag). In the first stage, 72 acoustic panels with dimension 500 % 500 % 35 mm were cast and prepared. The mechanical properties of the panels were then assessed in terms of their compressive and flexural strengths. Moreover, the durability properties of acoustic panels were studied using harsh conditions (freeze/thaw and carbonation tests). The efficiency of the lightweight panels was also assessed in terms of thermal properties. In the second stage, 50 acoustic panels were used to cover the floor area in a reverberation room. The acoustic absorption in diffuse field conditions was measured, and the interrupted random noise source method was used to record the sound pressure decay rate over time. Moreover, the acoustic properties of the panels were separately assessed by impedance tubes and airflow resistivity measurements. The recorded results from these two sound absorption evaluations were compared. Additionally, a comparative study was presented on the results of impedance tube measurements to compare the influence of casting volumes (large and small scales) on the sound absorption of the acoustic panels. In the last stage, a comparative study was implemented to clarify the effects of harsh conditions on the sound absorption of the acoustic panels. The results showed that casting scale had great impacts on the mechanical and physical properties. Additionally, it was revealed that harsh conditions improved the sound properties of acoustic panels due to their effects on the porous structure of materials.
Ključne besede: alkali activation, slag, acoustic panels
Objavljeno v DiRROS: 15.09.2023; Ogledov: 443; Prenosov: 237
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6. The potential of ladle slag and electric arc furnace slag use in synthesizing alkali activated materials; the influence of curing on mechanical propertiesMark Češnovar, Katja Traven, Barbara Horvat, Vilma Ducman, 2019, izvirni znanstveni članek Povzetek: Alkali activation is studied as a potential technology to produce a group of high performance building materials from industrial residues such as metallurgical slag. Namely, slags containing aluminate and silicate form a useful solid material when activated by an alkaline solution. The alkali-activated (AA) slag-based materials are promising alternative products for civil engineering sector and industrial purposes. In the present study the locally available electric arc furnace steel slag (Slag A) and the ladle furnace basic slag (Slag R) from different metallurgical industries in Slovenia were selected for alkali activation because of promising amorphous Al/Si rich content. Different mixtures of selected precursors were prepared in the Slag A/Slag R ratios 1/0, 3/1, 1/1, 1/3 and 0/1 and further activated with potassium silicate using an activator to slag ratio of 1:2 in order to select the optimal composition with respect to their mechanical properties. Bending strength of investigated samples ranged between 4 and 18 MPa, whereas compressive strength varied between 30 and 60 MPa. The optimal mixture (Slag A/Slag R = 1/1) was further used to study strength development under the influence of different curing temperatures at room temperature (R. T.), and in a heat-chamber at 50, 70 and 90 °C, and the effects of curing time for 1, 3, 7 and 28 days was furthermore studied. The influence of curing time at room temperature on the mechanical strength at an early age was found to be nearly linear. Further, it was shown that specimens cured at 70 °C for 3 days attained almost identical (bending/compressive) strength to those cured at room temperature for 28 days. Additionally, microstructure evaluation of input materials and samples cured under different conditions was performed by means of XRD, FTIR, SEM and mercury intrusion porosimetry (MIP).
Ključne besede: alkali activation, slag, influence of curing regime, FTIR
Objavljeno v DiRROS: 13.09.2023; Ogledov: 445; Prenosov: 239
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7. The Incorporation of steel slag into belite-sulfoaluminate cement clinkersLea Žibret, Katarina Šter, Maruša Mrak, Mojca Loncnar, Sabina Dolenec, 2021, izvirni znanstveni članek Povzetek: 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 asbelite, 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 steelslags 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.
Ključne besede: cements, BCSA, steel slag, secundary row materials, microstructure, clinker phase
Objavljeno v DiRROS: 01.08.2023; Ogledov: 430; Prenosov: 215
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8. The effect of crystalline waterproofing a dmixtures on the self-healing and permeability of concreteAnita Gojević, Vilma Ducman, Ivanka Netinger Grubeša, Ana Baričević, Ivana Banjad Pečur, 2021, izvirni znanstveni članek Povzetek: This paper investigates the effectiveness of a specific crystalline waterproofing admixture (CWA) in concrete as a function of a water–binder ratio. Four concrete mixes with and without CWA were prepared; two of them with a water–binder ratio of 0.45 and two of them with a water– binder ratio of 0.55. Water permeability and compressive strength were tested on hardened concrete specimens and self-healing of cracks over time was observed. Cement paste and CWA paste were prepared to clarify the results obtained on the concrete specimens. SEM and EDS and XRD and FTIR were performed on the hardened pastes to explain the mechanism of CWA working. The results show that the addition of CWA had no significant effect on the compressive strength of the concrete, but reduced the water penetration depth in the concrete, and the reduction was more effective for mixes with lower water–binder ratio. Regarding the self-healing effect, it can be concluded that the addition of CWA improves the crack healing in concrete, but the efficiency of self-healing is highly dependent on the initial crack width. The mechanisms involved in the reduction of water penetration depth and crack healing in concrete can be explained by different mechanisms; one is creation of the CSH gel from unreacted clinker grains, then formation carbonate, and additional mechanism is gel formation (highly expansive Mg-rich hydro-carbonate) from magnesium based additives. The presence of sodium silicate, which would transform into carbonate/bicarbonate, also cannot be excluded.
Ključne besede: slag, self healing concrete, crystal admixture, microstructural analysis
Objavljeno v DiRROS: 03.07.2023; Ogledov: 434; Prenosov: 316
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9. The deformation of alkali-activated materials at an early age under different curing conditionsMark Češnovar, Katja Traven, Vilma Ducman, 2021, izvirni znanstveni članek Povzetek: The production of alkali-activated materials (AAMs) is known for its environmentally friendly processing method, where several amorphous-rich aluminosilicate material sources combine with an alkali media solution to form solid, ceramic-like materials. In terms of the Si:Al, Na(K):Al, and Na(K):H2O ratios, the theory of AAM formation is quite well developed, but some open questions in the technology process remain, especially with regards to the means of curing, where the generation of defects can be persistent. Knowing that deformation is extremely high in the early ages, this study investigates the effects of temperature and moisture on shrinkage behavior within the first 72 h of AA pastes made from ladle (LS) and electric arc furnace (EAF) slag and activated by sodium silicate (Na2SiO3). The method to determine the deformation of alkali-activated slag-based materials, in terms of both autogenous and drying shrinkage, was based on the modified ASTM C1698-19 standard for the measurement of autogenous shrinkage in cement pastes. Autogenous deformation and strain were measured in four samples, using the standard procedure at room temperature, 40 and 60°C. Furthermore, using an adjusted method, nine samples were characterized for strain and partial surface pressure, while drying at room temperature, 40, or 60°C at a relative humidity of 30 or 90%. The results show that the highest rate of autogenous shrinkage occurred at a temperature of 60°C, followed by drying shrinkage at 60°C and 30% relative humidity, owing to the fact that the rate of evaporation was highest at this moisture content. The study aimed to provide guidance regarding selection of the optimal curing set in order to minimize deformations in slag-based alkali-activated materials. In the present case, curing at a temperature of around 40°C under lower moisture conditions for the first 24 h provided optimal mechanical properties for the slags investigated. The methodology might also be of use for other aluminosilicate sources such as metakaolin, fly ash, and mineral wool–based alkali-activated materials.
Ključne besede: alkali-activated materials, slag, drying, autogenous shrinkage, partial surface pressure, curing deformation
Objavljeno v DiRROS: 03.07.2023; Ogledov: 580; Prenosov: 252
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10. Mass concrete with EAF steel slag aggregate : workability, strength, temperature rise, and environmental performanceDavor Kvočka, Jakob Šušteršič, Alenka Mauko Pranjić, Ana Mladenovič, 2022, izvirni znanstveni članek Povzetek: Temperature control is the primary concern during the design and construction process of mass concrete structures. As the concrete production has an enormous negative environmental impact, the development of green mass concretes will eventually become as important as the thermal characteristics. Therefore, this paper investigates the use of Electric Arc Furnace (EAF) steel slag aggregate for the partial replacement of the natural aggregate in the production of mass concrete. The impact of EAF steel aggregate on mass concrete workability, strength, and thermal behaviour was analysed. In addition, a cradle-to-gate LCA study was conducted to evaluate the environmental footprint and sustainability potential of the tested mass concrete mixtures. The study results suggest that the use of EAF steel slag aggregate in combination with a low-heat cement with a high content of blast furnace slag can significantly lower the temperature, reduce the environmental impact, and increase the sustainability potential of mass concrete, while at the same time providing sufficient workability and compressive strength. The study results indicate that EAF steel slag can be upcycled into an aggregate for the production of green mass concrete mixtures.
Ključne besede: mass concrete, thermal stress, EAF steel slag, green concrete, LCA, sustainability, open access
Objavljeno v DiRROS: 31.05.2023; Ogledov: 502; Prenosov: 327
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