Characterization and Reuse of Slag

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Processing and Extractive Metallurgy".

Deadline for manuscript submissions: 29 August 2025 | Viewed by 6166

Special Issue Editors


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Guest Editor
Postgraduate Program in Materials Science and Engineering, Universidade Do Extremo Sul Catarinense, Criciuma 88806-000, Brazil
Interests: sustainable steelmaking; circular economy; extractive metallurgy; materials engineering

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Guest Editor
Departamento de Engenharia Metalúrgica e de Materiais, Instituto Federal do Espírito Santo, Vitória 29040-780, Brazil
Interests: steelmaking; sustainable steel production; development of synthetic slags; computational thermodynamics

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Guest Editor
Centro Federal de Educação Tecnológica de Minas Gerais, Timóteo 35180-008, Brazil
Interests: extractive metallurgy; pyrometallurgy; residues characterization

Special Issue Information

Dear Colleagues,

Slag is a byproduct generated in metallurgical processes, predominantly composed of oxides. Traditionally considered as a waste, slag is now valued as a resource due to technological advancements and environmental concerns. Its primary application is in civil construction, where it can be used as a base material for paving, in cement production, and as aggregate in concrete and mortar. Additionally, slag has applications in agriculture as a soil conditioner, in the abrasive industry for blasting materials, and in the production of thermal and acoustic insulation. Besides being used as a raw material in various applications, slags can also be rich in strategic metals.

The reuse of slag contributes to the circular economy, reducing the need for new resource extraction and minimizing the environmental impact of metallurgical processes. Thus, slag, once seen as waste, is now a byproduct with multiple applications, exemplifying how innovation and environmental responsibility can turn challenges into opportunities.

This Special Issue invites researchers to submit papers that include original scientific research related to the characterization and reuse routes of slags. The Special Issue focuses on the following topics: (1) Chemical, physical, mineralogical, and environmental characterizations of slags; (2) Processing routes; and (3) The valorization of slags. Other applications of slags are also encouraged for publication in this Special Issue.

Dr. Eduardo Junca
Prof. Dr. Felipe Fardin Grillo
Prof. Dr. Jorge Luís Coleti
Guest Editors

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Keywords

  • slag valorization
  • circular economy
  • slag processing
  • metallurgical byproduct

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Published Papers (6 papers)

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Research

16 pages, 5962 KiB  
Article
Treatment of Metallurgical Residues by Chemical Modification, Reduction, and Phase Modification for Metal Recovery and Slag Utilization
by Klaus Doschek-Held, Anna Christine Krammer, Florian Roman Steindl, Christoph Gatschlhofer, Zlatko Raonic and Dominik Wohlmuth
Minerals 2025, 15(4), 408; https://doi.org/10.3390/min15040408 - 13 Apr 2025
Viewed by 197
Abstract
Advancing material efficiency in the steel and cement industry is essential for achieving climate goals. One approach to addressing this is to increase the provisioning of alternative reactive binder materials from residues, in this case, from the steel industry. Different mixtures of identified [...] Read more.
Advancing material efficiency in the steel and cement industry is essential for achieving climate goals. One approach to addressing this is to increase the provisioning of alternative reactive binder materials from residues, in this case, from the steel industry. Different mixtures of identified residues are evaluated for metal recovery and suitability as supplementary cementitious material. For this purpose, suitable combinations are modeled according to specified quality requirements from the cement industry. These mixtures are heated up to 1600 °C for a targeted reduction of predominantly transition metal oxides and a separation into a mineral fraction. Subsequently, controlled cooling of the molten material is implemented through water granulation. The produced granulate is crushed and sieved, and finally, the metallic and mineral fractions are magnetically separated. The chemical modification, reduction, and phase modification are tested to prevent landfilling and provide alternative secondary resources for the steel and cement industry. According to the results, it is possible to recover metals from metallurgical residues and simultaneously separate the modified mineral fraction as an alternative cement constituent. These findings will be further investigated through additional research to identify the variables that influence and impact/affect the reduction efficiency. Full article
(This article belongs to the Special Issue Characterization and Reuse of Slag)
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20 pages, 5204 KiB  
Article
Optimization of Ultra-High-Performance Concrete Using a Clinker-Free Binder and Iron Mine Tailings Aggregate
by Hocine Heraiz, Xinli Mu, Jiajie Li, Bolan Lei, Siqi Zhang, Yunyun Li, Sitao Zhu, Wen Ni and Michael Hitch
Minerals 2025, 15(1), 28; https://doi.org/10.3390/min15010028 - 29 Dec 2024
Cited by 2 | Viewed by 766
Abstract
This study investigates the use of iron mine tailings (ITs) as a fine aggregate and a clinker-free binder composed of ground granulated blast-furnace slag (GBFS), desulfurization gypsum (DG), and basic oxygen furnace slag (BOFS) to produce low-cost ultra-high-performance concrete (UHPC). The research optimizes [...] Read more.
This study investigates the use of iron mine tailings (ITs) as a fine aggregate and a clinker-free binder composed of ground granulated blast-furnace slag (GBFS), desulfurization gypsum (DG), and basic oxygen furnace slag (BOFS) to produce low-cost ultra-high-performance concrete (UHPC). The research optimizes the UHPC base by evaluating the impact of key parameters, including the BOFS to GBFS ratio, DG content, BOFS fineness, and binder-to-sand ratio on compressive strength. The study also compares the use of iron mine tailings and silica sand as fine aggregates, demonstrating that tailings are a viable substitute. The results show that the optimal mix, consisting of a 1:1 BOFS to GBFS ratio, 15% DG, and 400 m2/kg BOFS fineness, achieves a compressive strength of 113.7 MPa after 28 days when using iron mine tailings as fine aggregate. Microstructural analysis through X-ray diffraction (XRD), thermogravimetry (TG), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) reveal that the primary hydration products—C-S-H gel and AFt—contribute to the dense and strong microstructure of the UHPC. This research offers a sustainable approach to producing cost-effective UHPC by utilizing industrial waste materials, providing a promising solution for reducing both environmental impact and production costs in construction. Full article
(This article belongs to the Special Issue Characterization and Reuse of Slag)
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17 pages, 2851 KiB  
Article
Artificial Neural Network-Based Non-Linear Modeling and Simulation of CaO-SiO2-Al2O3-MgO Blast Furnace Slag Viscosity
by Patrick dos Anjos, Jorge Luís Coleti, Eduardo Junca, Felipe Fardin Grillo and Marcelo Lucas Pereira Machado
Minerals 2024, 14(11), 1160; https://doi.org/10.3390/min14111160 - 16 Nov 2024
Viewed by 916
Abstract
Blast furnace slags are formed by CaO-SiO2-Al2O3-MgO systems and have several physical characteristics, one of which is viscosity. Viscosity is an important variable for the operation and blast furnace performance. This work aimed to model viscosity through [...] Read more.
Blast furnace slags are formed by CaO-SiO2-Al2O3-MgO systems and have several physical characteristics, one of which is viscosity. Viscosity is an important variable for the operation and blast furnace performance. This work aimed to model viscosity through linear and non-linear models in order to obtain a model with precision and accuracy. The best model constructed was a non-linear model by artificial neural networks that presented 23 nodes in the first hidden layer and 24 nodes in the second hidden layer with 6 input variables and 1 output variable named ANN 23-24. ANN 23-24 obtained better statistical evaluations in relation to 11 different literature equations for predicting viscosity in CaO-SiO2-Al2O3-MgO systems. ANN 23-24 was also subjected to numerical simulations in order to demonstrate the validation of the non-linear model and presented applications such as viscosity prediction, calculation of the inflection point in the viscosity curve by temperature, the construction of ternary diagrams with viscosity data, and the construction of iso-viscosity curves. Full article
(This article belongs to the Special Issue Characterization and Reuse of Slag)
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20 pages, 18605 KiB  
Article
Enhancing Mechanical Properties of Expansive Soil Through BOF Slag Stabilization: A Sustainable Alternative to Conventional Methods
by Arailym Mustafayeva, Sung-Woo Moon, Alfrendo Satyanaga and Jong Kim
Minerals 2024, 14(11), 1145; https://doi.org/10.3390/min14111145 - 12 Nov 2024
Cited by 2 | Viewed by 1345
Abstract
This study investigates the stabilization of expansive soil using basic oxygen furnace (BOF) slag, an eco-friendly steel by-product, as an alternative to conventional stabilizers like ordinary Portland cement. By evaluating varying concentrations of BOF slag and lime as an activator, the research aims [...] Read more.
This study investigates the stabilization of expansive soil using basic oxygen furnace (BOF) slag, an eco-friendly steel by-product, as an alternative to conventional stabilizers like ordinary Portland cement. By evaluating varying concentrations of BOF slag and lime as an activator, the research aims to improve the soil’s mechanical properties, addressing issues like low bearing capacity and high shrink–swell potential. Bentonite clay was treated with different BOF slag ratios (10%, 20%, and 30%) and activated with lime (1%, 3%, and 5%). After mixing and compaction, samples were cured and tested for unconfined compressive strength (UCS), shear wave velocity (BE), and free swell. Microscopic analyses (SEM) provided insight into structural changes post-stabilization, revealing improved properties with increased BOF and lime concentrations. Notably, stabilization with 30% BOF slag and 5% lime achieves a compressive strength of 810 kPa, meeting the minimum subgrade soil stabilization requirement (700 kPa) set by the Federal Highway Administration. This research underscores the potential of BOF slag as a sustainable and practical material for bentonite clay stabilization, offering a promising solution for enhancing soil properties while contributing to environmental sustainability through industrial by-product repurposing. Full article
(This article belongs to the Special Issue Characterization and Reuse of Slag)
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20 pages, 1113 KiB  
Article
Potential for the Recovery of Selected Metals and Critical Raw Materials from Slags from Polymineral Zn–Pb Ore Metallurgy—Part II
by Henryk Świnder, Paweł Lejwoda, Piotr Krawczyk, Magdalena Cempa and Arkadiusz Bauerek
Minerals 2024, 14(11), 1091; https://doi.org/10.3390/min14111091 - 28 Oct 2024
Viewed by 864
Abstract
This paper presents the results of research on the possibility to obtain CRMs (REEs) and industrial metals (Zn) from slag as a waste generated as part of zinc and lead extraction processes. Physicochemical methods were used to separate CRM and Zn concentrates: magnetic [...] Read more.
This paper presents the results of research on the possibility to obtain CRMs (REEs) and industrial metals (Zn) from slag as a waste generated as part of zinc and lead extraction processes. Physicochemical methods were used to separate CRM and Zn concentrates: magnetic separation, sintering with NaOH and leaching with selected mineral acids. After analysing the obtained results, it was found that the use of concentrated hydrochloric acid and a temperature of 363 K for leaching was effective in separating REEs from slags obtained from current production. The recovery rate in this case ranged from 83.73% for La to 98.03% for Eu. For slag samples (M1) obtained from current production from ZGH Bolesław S.A.(Poland) as well as HC Miasteczko Śląskie S.A. (Poland) and treated with concentrated HCl, the leaching level of Bi, Zn, Ni, Mn and P exceeded 90% compared to the content in the reference sample. For a historical slag sample from Ruda Śląska (Poland), treatment with concentrated HCl yielded a high leaching level of Cd (70.90%), Pb (78.66%), As (72.49%) and Mo (61.90%). A concentrate containing 1.64% of REEs and 67.1% of Zn was isolated from the solutions obtained after leaching by precipitation. An economic analysis of an REE concentrate extraction facility was also performed. For an operation of 17 years, the calculated NPV was −26,352,644 million EUR. The obtained results indicate that, for the analysed facility, recovering metals and critical raw materials from slag as a waste mass is not economically effective. Full article
(This article belongs to the Special Issue Characterization and Reuse of Slag)
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25 pages, 5747 KiB  
Article
Potential for the Recovery of Selected Metals and Critical Raw Materials from Slags from Polymineral Zn–Pb Ore Metallurgy—Part I
by Magdalena Cempa, Paweł Lejwoda, Klaudia Karabela, Anna Pieprzyca, Henryk Świnder and Arkadiusz Bauerek
Minerals 2024, 14(10), 1050; https://doi.org/10.3390/min14101050 - 19 Oct 2024
Cited by 2 | Viewed by 1380
Abstract
Slags from the Silesia–Cracow Upland (Poland), including ten historical slags (deposited in waste dumps) and four contemporary slags (from current production), were examined to compare their chemical and mineralogical properties as well as to assess their potential for the recovery of selected metals [...] Read more.
Slags from the Silesia–Cracow Upland (Poland), including ten historical slags (deposited in waste dumps) and four contemporary slags (from current production), were examined to compare their chemical and mineralogical properties as well as to assess their potential for the recovery of selected metals and critical raw materials. The historical slags associated with the smelting of polymetallic ores originating from Mississippi Valley-type (MVT) deposits consisted primarily of gypsum. The contemporary slags, obtained from industrial waste rich in zinc and lead, were predominantly spinels (magnesium-aluminate and ferric) that exhibited higher iron content (up to 46.6 wt% of Fe2O3) compared to the historical slags (up to 26.1 wt% of Fe2O3). The zinc content was similar for both the slag types (3.5 wt% Zn). The average titanium and arsenic contents in the old and contemporary slags were at the same level as well, with 0.21 wt% (Ti) and 0.13 wt% (As), respectively. The contemporary slags contained higher levels of critical raw materials, such as cobalt, nickel, copper, and manganese, compared to the historical slags. Rare earth elements (REEs) were also more abundant in the contemporary slags, with an average content of 212 ppm, while the historical slags averaged 124 ppm. These findings underscore the potential for recovering valuable metals and critical raw materials from such slags, presenting opportunities for resource optimisation and environmental management. Full article
(This article belongs to the Special Issue Characterization and Reuse of Slag)
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