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Utilisation of Industrial Byproducts for Materials and Metallurgical Applications

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

Deadline for manuscript submissions: closed (15 October 2020) | Viewed by 41421

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Special Issue Editors

Dr. Pramod Koshy

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Guest Editor

School of Materials Science and Engineering, University of New South Wales, Kensington, Australia
Interests: ceramics; resources engineering and extractive metallurgy; environmental engineering; nanobiotechnology

Prof. Dr. Ao Huang

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Co-Guest Editor

The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, China
Interests: refractories; slag; steelmaking; interfacial behavior; corrosion

Special Issue Information

Dear Colleagues,

With the rapid industrial growth and the associated improvement in living standards, there are increasing volumes of waste materials (industrial by-products) that are being produced by different industries. Most of these materials pose significant risks to the environment and health and present a serious challenge when it comes to their disposal, leading to their accumulation at the industry site or landfill. One such material is fly ash, which is currently produced in such high volumes that it is considered to be one of the largest resources globally, even though it is an industrial waste. Furthermore, with the increasing use of mineral resources by industries, there is currently a rapid decline in the quantities of high-quality resources, thereby prompting the need for increased research on the utilisation of low-quality and industrial byproduct materials to ensure the competitiveness and sustainability of the metallurgical and materials industries in the coming decades. This Special Issue will focus on recent advances in materials and technologies related to utilisation of industrial byproducts such as fly ash and blast furnace slag, metallic and polymer wastes from industries and their characterisation using different analytical tools.

Dr. Pramod Koshy
Prof. Dr. Ao Huang
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Minerals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

industrial byproducts
metallurgy
fly ash
slag
waste plastics

Published Papers (13 papers)

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Research

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22 pages, 10735 KiB

Open AccessArticle

Long-Term Strength Evolution in Ambient-Cured Solid-Activator Geopolymer Compositions

by Vincent Wong, William Jervis, Benjamin Fishburn, Takafumi Numata, William Joe, Aditya Rawal, Charles Christopher Sorrell and Pramod Koshy

Minerals 2021, 11(2), 143; https://0-doi-org.brum.beds.ac.uk/10.3390/min11020143 - 30 Jan 2021

Cited by 10 | Viewed by 3178

Abstract

The major downsides of cement manufacturing are the high CO₂ emissions and high energy usage. Geopolymers, which are fabricated by activation of blends of fly ash (FA) and ground granulated blast furnace slag (GGBFS) using an alkaline activator, offer a promising solution to this issue. However, to enhance the replacement of cement in construction applications, geopolymer compositions have to be designed such that they can be activated on site by just adding water, similar to how cements are used. Therefore, the present work uses solid sodium metasilicate (MS, Na₂SiO₃) as the alkaline activator in order to design an add-water-style FA/GGBFS-based geopolymer composition. These compositions were designed by optimising the binder (FA/GGBFS) ratio, Na₂SiO₃/binder ratio, and water/binder ratio individually to assess the effects of these parameters on the setting times and mechanical (flexural and compressive) strengths over extended curing times (three months). The major factors affecting the strength development and setting times (initial and final) were the amounts of GGBFS and Na₂SiO₃, with the former demonstrating the more dominant effect. The consistent strength development with curing time was attributed to calcium aluminium silicate hydrate (CASH) gel formation in the early curing times which was affected by the slag addition levels, and sodium aluminium silicate hydrate (NASH) gel formation at later curing times which was influenced by the metasilicate addition levels. The metasilicate amounts were observed to impact on CASH gel formation in early stage curing. Geopolymer compositions with FA/GGBFS ratio of 35/65 and MS/water ratios of 0.2 showed high compressive strengths of ~70 MPa at 28 days, which are superior to values seen in conventional ordinary Portland cement (OPC) mixes for the same curing times. Full article

(This article belongs to the Special Issue Utilisation of Industrial Byproducts for Materials and Metallurgical Applications)

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16 pages, 4477 KiB

Open AccessEditor’s ChoiceArticle

Fly Ash Utilisation in Mullite Fabrication: Development of Novel Percolated Mullite

by Pramod Koshy, Naomi Ho, Vicki Zhong, Luisa Schreck, Sandor Alex Koszo, Erik J. Severin and Charles Christopher Sorrell

Minerals 2021, 11(1), 84; https://0-doi-org.brum.beds.ac.uk/10.3390/min11010084 - 16 Jan 2021

Cited by 6 | Viewed by 2872

Abstract

Fly ash is an aluminosilicate and the major by-product from coal combustion in power stations; its increasing volumes are major economic and environmental concerns, particularly since it is one of the largest mineral resources based on current estimates. Mullite (3Al₂O₃·2SiO₂) is the only stable phase in the Al₂O₃-SiO₂ system and is used in numerous applications owing to its high-temperature chemical and mechanical stabilities. Hence, fly ash offers a potential economical resource for mullite fabrication, which is confirmed by a review of the current literature. This review details the methodologies to utilise fly ash with different additives to fabricate what are described as porous interconnected mullite skeletons or dense mullite bodies of approximately stoichiometric compositions. However, studies of pure fly ash examined only high-Al₂O₃ forms and none of these works reported long-term, high-temperature, firing shrinkage data for these mullite bodies. In the present work, high-SiO₂ fly ashes were used to fabricate percolated mullite, which is demonstrated by the absence of firing shrinkage upon long-term high-temperature soaking. The major glass component of the fly ash provides viscosities suitably high for shape retention but low enough for ionic diffusion and the minor mullite component provides the nucleating agent to grow mullite needles into a direct-bonded, single-crystal, continuous, needle network that prevents high-temperature deformation and isolates the residual glass in the triple points. These attributes confer outstanding long-term dimensional stability at temperatures exceeding 1500 °C, which is unprecedented for mullite-based compositions. Full article

(This article belongs to the Special Issue Utilisation of Industrial Byproducts for Materials and Metallurgical Applications)

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24 pages, 4825 KiB

Open AccessArticle

Development of Low-Alkali, Fly Ash/Slag Geopolymers: Predictive Strength Modelling and Analyses of Impact of Curing Temperatures

by Supphatuch Ukritnukun, Pramod Koshy, Clayton Feng, Aditya Rawal, Arnaud Castel and Charles Christopher Sorrell

Minerals 2021, 11(1), 60; https://0-doi-org.brum.beds.ac.uk/10.3390/min11010060 - 11 Jan 2021

Cited by 3 | Viewed by 2098

Abstract

The present work analyses the effects of curing temperature (25, 40, 60 °C for 24 h), silicate modulus Ms value (1.5, 1.7, 2.0), and slag content (10, 20, 30, 40 wt%) on the compressive strength development (1, 7, 14, 28 days) of low-alkali geopolymer mortars with matrices from fly ash and blast furnace slag. These data were used to generate predictive models for 28-day compressive strength as a function of curing temperature and slag content. While the dominant variable for the 1-day compressive strength was the curing temperature, the slag content was dominant for the 28-day compressive strength. The ratio of the 1-day and 28-day compressive strengths as a function of curing temperature, Ms value, and slag content allows prediction of the maximal possible curing temperature and shows cold-weather casting to present an obstacle to setting. These data also allow prediction of the 28-day compressive strength using only the 1-day compressive strength. Full article

(This article belongs to the Special Issue Utilisation of Industrial Byproducts for Materials and Metallurgical Applications)

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18 pages, 11563 KiB

Open AccessArticle

Recovery of Iron from Copper Slag Using Coal-Based Direct Reduction: Reduction Characteristics and Kinetics

by Hanquan Zhang, Chaojie Hu, Wangjie Gao and Manman Lu

Minerals 2020, 10(11), 973; https://0-doi-org.brum.beds.ac.uk/10.3390/min10110973 - 31 Oct 2020

Cited by 14 | Viewed by 4003

Abstract

The Fe₃O₄ and Fe₂SiO₄ in copper slag were successfully reduced to metallic iron by coal-based direct reduction. Under the best reduction conditions of 1300 °C reduction temperature, 30 min reduction time, 35 wt.% coal dosage, and 20 wt.% CaO dosage (0.75 binary basicity), the Fe grade of obtained iron concentration achieved 91.55%, and the Fe recovery was 98.13%. The kinetic studies on reduction indicated that the reduction of copper slag was controlled by the interfacial reaction and carbon gasification at 1050 °C. When at a higher reduction temperature, the copper slag reduction was controlled by the diffusion of the gas. The integral kinetics model research illustrated that the reaction activation energy increased as the reduction of copper slag proceeded. The early reduction of Fe₃O₄ needed a low reaction activation energy. The subsequent reduction of Fe₂SiO₄ needed higher reaction activation energy compared with that of Fe₃O₄ reduction. Full article

(This article belongs to the Special Issue Utilisation of Industrial Byproducts for Materials and Metallurgical Applications)

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20 pages, 3403 KiB

Open AccessArticle

Predictive Model of Setting Times and Compressive Strengths for Low-Alkali, Ambient-Cured, Fly Ash/Slag-Based Geopolymers

by Supphatuch Ukritnukun, Pramod Koshy, Aditya Rawal, Arnaud Castel and Charles Christopher Sorrell

Minerals 2020, 10(10), 920; https://0-doi-org.brum.beds.ac.uk/10.3390/min10100920 - 17 Oct 2020

Cited by 26 | Viewed by 2913

Abstract

The effects of curing temperature, blast furnace slag content, and Ms on the initial and final setting times, and compressive strengths of geopolymer paste and mortars are examined. The present work demonstrates that ambient-cured geopolymer pastes and mortars can be fabricated without requiring high alkalinity activators or thermal curing, provided that the ratios of Class F fly ash (40–90 wt%), blast furnace slag (10–60 wt%), and low alkalinity sodium silicate (Ms = 1.5, 1.7, 2.0) are appropriately balanced. Eighteen mix designs were assessed against the criteria for setting time and compressive strength according to ASTM C150 and AS 3972. Using these data, flexible and reproducible mix designs in terms of the fly ash/slag ratio and Ms were mapped and categorised. The optimal mix designs are 30–40 wt% slag with silicate modulus (Ms) = 1.5–1.7. These data were used to generate predictive models for initial and final setting times and for ultimate curing times and ultimate compressive strengths. These projected data indicate that compressive strengths >100 MPa can be achieved after ambient curing for >56 days of mixes of ≥40 wt% slag. Full article

(This article belongs to the Special Issue Utilisation of Industrial Byproducts for Materials and Metallurgical Applications)

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19 pages, 3203 KiB

Open AccessArticle

Development of Slurry Surfacing with Electric Arc Furnace Slag for Pavements with Friction Problems

by Juan María Terrones-Saeta, Jorge Suárez-Macías, Francisco Javier Iglesias-Godino and Francisco Antonio Corpas-Iglesias

Minerals 2020, 10(10), 878; https://0-doi-org.brum.beds.ac.uk/10.3390/min10100878 - 01 Oct 2020

Cited by 4 | Viewed by 1607

Abstract

Pavement maintenance is an essential activity for maintaining the quality of the pavements. It is common for the ageing pavement to present problems of friction, so a proper solution must be provided. In this work, electric arc furnace slags are incorporated in slurry surfacing to provide adequate friction with this technique. The electric arc furnace slag was studied with physical, chemical, and mechanical tests to evaluate its suitability in the formation of the bituminous mixture. At the same time, different groups of samples were made with increasing percentages of bitumen emulsion and slag as coarse aggregate, determining the wear of the different families and the cohesion. The results reflected the excellent characteristics of the electric arc furnace slags, and an optimal combination of materials (slag, aggregate, water, and bitumen emulsion) could be obtained to develop slurry surfacing applicable to important traffic roads. This provided a use for the electric arc furnace slag in which its mechanical properties were used and a sustainable bituminous mixture with excellent characteristics and respectful of the environment was developed. Full article

(This article belongs to the Special Issue Utilisation of Industrial Byproducts for Materials and Metallurgical Applications)

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21 pages, 6682 KiB

Open AccessArticle

Development of Porous Asphalt with Bitumen Emulsion, Electric arc Furnace Slag and Cellulose Fibers for Medium Traffic Roads

by Juan María Terrones-Saeta, Jorge Suárez-Macías, Francisco Javier Iglesias-Godino and Francisco Antonio Corpas-Iglesias

Minerals 2020, 10(10), 872; https://0-doi-org.brum.beds.ac.uk/10.3390/min10100872 - 01 Oct 2020

Cited by 9 | Viewed by 2631

Abstract

The construction of road infrastructure is one of the most polluting activities that exists today. Therefore, the use of waste from other industries is an excellent solution, since it reduces the consumption of raw materials, reduces CO₂ emissions and avoids the disposal of waste in a landfill. In this study, electric arc furnace slag, cellulose fibers from the papermaking industry and bitumen emulsion were used for the conformation of sustainable and porous bituminous mixtures. Electric arc furnace slag was used as a high-resistance aggregate with a capacity sufficient to support traffic loads. Cellulose fibers were added to increase the percentage of binder in the mixture without bleeding problems, thereby achieving greater tensile strength. To do this, first the waste was physically and chemically characterized, then different mixtures were conformed and finally the mixtures were studied by means of the loss by wear and Marshall tests. The results reflected an optimal combination of materials that provided the best results in the mechanical tests, obtaining much better results than the mixtures with discontinuous grading and traditional bitumen emulsion. Therefore, a sustainable, porous and economical mixture for road use is obtained in this research. Full article

(This article belongs to the Special Issue Utilisation of Industrial Byproducts for Materials and Metallurgical Applications)

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12 pages, 5455 KiB

Open AccessArticle

Impact of Fly Ash as a Raw Material on the Properties of Refractory Forsterite–Spinel Ceramics

by Martin Nguyen and Radomír Sokolář

Minerals 2020, 10(9), 835; https://0-doi-org.brum.beds.ac.uk/10.3390/min10090835 - 22 Sep 2020

Cited by 7 | Viewed by 2681

Abstract

This article examines the process for the synthesis of forsterite–spinel (2MgO·SiO₂/MgO·Al₂O₃) refractory ceramics from fly ash and alumina as sources of aluminum oxide. Raw materials were milled, mixed in different ratios and sintered at 1500 °C for 2 h. Sintered samples were characterized by XRD, thermal analyses and SEM. Porosity, water absorption, bulk density, refractoriness, refractoriness under load and thermal shock resistance were also investigated. The impact of fly ash as a raw material was investigated in accordance with the resulting properties and microstructure of samples with fly ash and alumina as the raw materials. Due to the positive effect of flux oxides (iron oxides and alkalis) on sintering, the mullite contained in fly ash completely decomposed into silica and alumina, which, together with magnesium oxide, formed spinel. This led to improved microstructural and mechanical properties and thermal shock resistance. In particular, mixtures with 10 wt.% and 20 wt.% of fly ash had the most promising results compared to alumina mixtures. Both modulus of rupture and thermal shock resistance were improved, while the impact on refractory properties was minimal. The novelty of this research lies in the recycling of fly ash, a by-product from coal-burning power plants, into a raw material for the production of forsterite–spinel refractory ceramics. Full article

(This article belongs to the Special Issue Utilisation of Industrial Byproducts for Materials and Metallurgical Applications)

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9 pages, 4447 KiB

Open AccessArticle

Effects of Step-Wise Acid Leaching with HCl on Synthesis of Zeolitic Materials from Paper Sludge Ash

by Takaaki Wajima

Minerals 2020, 10(5), 402; https://0-doi-org.brum.beds.ac.uk/10.3390/min10050402 - 29 Apr 2020

Cited by 6 | Viewed by 2310

Abstract

Incinerated ash with a relatively high Ca content, paper sludge ash, was converted to zeolitic materials with high cation-exchange capacities (CECs) by aging at 80 °C in NaOH solution via step-wise acid leaching with HCl to reduce the ash Ca content. The extraction of Ca, Mg, Si, and Al from the ash into the acid solutions during leaching and the products obtained from the leached ash by reaction with an alkali were examined. The contents of Ca and Mg in the ash were more easily extracted from the ash than those of Si and Al in the initial leaching. The leachant pH decreased with increasing numbers of leaching steps, and the amounts of Si, Al, and Ca extracted from the ash increased as a result of the dissolution of gehlenite (Ca₂Al₂SiO₇), one of the main minerals in the ash. Zeolites A and P were synthesized from the leached ashes, and hydroxysodalite was synthesized from the raw ash. With increasing numbers of leaching steps of the ash, the obtained product contained lower released Ca, whereas the product contained higher released Na and has higher CEC, depending on the zeolite phases in the product. The product with the highest CEC was synthesized from third-leached ash, and its CEC was 1.5 mmol/g, which is about four times higher than that of the raw ash (0.4 mmol/g). Full article

(This article belongs to the Special Issue Utilisation of Industrial Byproducts for Materials and Metallurgical Applications)

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12 pages, 6141 KiB

Open AccessArticle

Structure and Phase Changes of Nickel Slag in Oxidation Treatment

by Xiaoming Li, Xinyi Zhang, Xuyuan Zang and Xiangdong Xing

Minerals 2020, 10(4), 313; https://0-doi-org.brum.beds.ac.uk/10.3390/min10040313 - 31 Mar 2020

Cited by 5 | Viewed by 2384

Abstract

To overcome the difficulty in the direct reduction of Fe₂SiO₄ in nickel slag, the isothermal oxidation of the nickel slag was conducted between 300 and 1000 °C. Its morphology and phase composition after oxidation at 300–1000 °C for 5–30 min are analyzed by means of Scanning electron microscopy, X-ray diffraction, and thermodynamic calculation. The results show that oxidation can effectively promote the transformation of Fe²⁺ into Fe³⁺ in nickel slag. At 900 °C, the oxidation rate of element Fe reaches 95%. Fe²⁺ in Fe₂SiO₄ is oxidized to generate Fe₂O₃, and the unit cell volume decreases from 301.75 Å³ to 297.72 Å³ with the increase in temperature. At the same time, a large number of pores appear in the particle, which reduces the mass transfer resistance of gas in the particle during the reduction process, accelerates the reduction speed, and is conducive to strengthening the reduction. Therefore, the oxidation treatment of nickel slag can improve its phase composition, thus benefiting the subsequent reduction. Full article

(This article belongs to the Special Issue Utilisation of Industrial Byproducts for Materials and Metallurgical Applications)

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15 pages, 1316 KiB

Open AccessEditor’s ChoiceArticle

Computational Modeling and Prediction on Viscosity of Slags by Big Data Mining

by Ao Huang, Yanzhu Huo, Juan Yang, Huazhi Gu and Guangqiang Li

Minerals 2020, 10(3), 257; https://0-doi-org.brum.beds.ac.uk/10.3390/min10030257 - 12 Mar 2020

Cited by 16 | Viewed by 3535

Abstract

The viscosity of slag is a key factor affecting metallurgical efficiency and recycling, such as metal-slag reaction and separation, as well as slag wool processing. In order to comprehensively clarify the variation of the slag viscosity, various data mining methods have been employed to predict the viscosity of the slag. In this study, a more advanced dual-stage predictive modeling approach is proposed in order to accurately analyze and predict the viscosity of slag. Compared with the traditional single data mining approach, the proposed method performs better with a higher recall rate and low misclassification rate. The simulation results show that temperature, SiO₂, Al₂O₃, P₂O₅, and CaO have greater influences on the slag’s viscosity. The critical temperature for onset of the important influence of slag composition is 980 °C. Furthermore, it is found that SiO₂ and P₂O₅ have positive correlations with slag’s viscosity, while temperature, Al₂O₃, and CaO have negative correlations. A two-equation model of six-degree polynomial combined with Arrhenius formula is also established for the purpose of providing theoretical guidance for industrial application and reutilization of slag. Full article

(This article belongs to the Special Issue Utilisation of Industrial Byproducts for Materials and Metallurgical Applications)

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11 pages, 5453 KiB

Open AccessArticle

Experimental Study on Strengthening Carbothermic Reduction of Vanadium-Titanium-Magnetite by Adding CaF₂

by Xiangdong Xing, Yueli Du, Jianlu Zheng, Yunfei Chen, Shan Ren and Jiantao Ju

Minerals 2020, 10(3), 219; https://0-doi-org.brum.beds.ac.uk/10.3390/min10030219 - 28 Feb 2020

Cited by 11 | Viewed by 2173

Abstract

The effects and reduction mechanisms of carbothermic reduction of vanadium–titanium–magnetite were studied by adding various mass fractions of CaF₂ ranging from 0%, 1%, 3%, 5% to 7%. The results showed that the proper CaF₂ addition could strengthen the carbothermic reduction of vanadium–titanium–magnetite while the excessive amounts will weaken the promotive effect, hence the appropriate dosage was determined to be 3 mass%. The CaF₂ was favorable for the carbon gasification reaction, where it increased the partial pressure of CO inside briquette and caused the lattice distortion of vanadium–titanium–magnetite. The reaction improved the reduction process and accelerated the reduction rate. The appearance of 3CaO·2SiO₂·CaF₂ and other complex compounds with low melting point facilitated the aggregation and growth of the slag and the iron, which increased the concentration of iron grains and the aggregation level of the slag. Full article

(This article belongs to the Special Issue Utilisation of Industrial Byproducts for Materials and Metallurgical Applications)

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Review

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28 pages, 3588 KiB

Open AccessReview

Progress on the Industrial Applications of Red Mud with a Focus on China

by Hua Zeng, Fei Lyu, Wei Sun, Hai Zhang, Li Wang and Yanxiu Wang

Minerals 2020, 10(9), 773; https://0-doi-org.brum.beds.ac.uk/10.3390/min10090773 - 31 Aug 2020

Cited by 34 | Viewed by 8267

Abstract

Red mud (RM), also called bauxite residue, is a strong alkaline industrial waste generated during the alumina production process. The annual production of RM in China is large, but its average utilization rate is low (only 4%). High generation and low consumption make the disposal of RM mainly by stockpiling, which has caused serious heavy metal pollution and radioactive contamination. In this paper, the various industrial utilization methods of RM in China during the past 60 years have been introduced. Moreover, some recent industrial progresses were referred. The results show that RM can be widely used in building materials, valuable metals extraction, and some novel utilization methods, such as silica-calcium fertilizer, inorganic polymer material and desulfurizer. Most of the industrial utilization methods of RM have been used until now and some successfully applied to other aluminum plants, providing some feasible routes for a large amount utilization of RM. Some industrial utilization methods (such as oil well cement and calcium silicon fertilizer) have not been used due to some problems that cannot be ignored, but it provided a lot of valuable experience and was helpful for the subsequent RM utilization. Moreover, some novel and feasible RM utilization methods were proposed and successfully industrialized, which showed that RM has a broader application prospect. Many actual practices showed that the best way to safely dispose of RM was to develop technology that could consume large amounts of RM or transform it into secondary resources, which may need more time and effort. Full article

(This article belongs to the Special Issue Utilisation of Industrial Byproducts for Materials and Metallurgical Applications)

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