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Slag solidification behavior significantly influences the tapping of the Zn fuming process and slag valorization. In this work, the effect of ZnO and CaO concentration on slag solidification was investigated under a pO 2 of approximately 10−10 atm using confocal laser scanning microscopy (CLSM) at various cooling rates. It was concluded that in the low CaO slag, the ZnO increased the onset formation temperature of the fayalite phase. An increase in CaO concentration facilitated wustite precipitation and prevented spinel formation in the slag at cooling rates exceeding 1 °C/s, while it enhanced melilite generation and inhibited fayalite precipitation in the slag at cooling rates below 1 °C/s. Furthermore, the slag mineralogy was studied as a function of equilibration temperature and CaO concentration of the slag through water quenching experiments under the Ar atmosphere. When slags with a CaO concentration of 3–20 wt% were quenched from 1050 to 1200 °C, the amorphous and spinel phases were observed in all quenched slags, whereas the wustite phase was only identified in slags with a CaO concentration above 10 wt%. Additionally, the fayalite phase was detected in slags containing 3–5 wt% CaO, quenched at temperatures of 1150–1050 °C. Notably, as the quenching temperature decreases and the CaO concentration increases, the observed phases in the quenched slag become more complex, and the solid particles grow coarser. The FeO t -SiO 2 -(4.7–5.7 wt%)ZnO-(8.3–10.1 wt%)Al 2 O 3 –CaO-1.3 wt%MgO-1.1 wt%Cr 2 O 3 (FeO/SiO 2 = 1.44) slags with a CaO concentration of below 20 wt% is suggested to be quenched from 1150 °C or 1200 °C to prevent the precipitation of a SiO 2 -containing phase and coarse wustite. [ABSTRACT FROM AUTHOR]

The corrosion behavior of novel MgO–Mg 1.08 Al 1.84 Ti 0.08 O 4 refractories was investigated as a potential replacement for traditional MgO–MgAl 2 O 4 refractories as the inner lining of RH snorkels. The incorporation of Mg 1.08 Al 1.84 Ti 0.08 O 4 fine powder with dense microstructure resulted in superior densification and mechanical strength compared to traditional MgO–MgAl 2 O 4 refractories. The novel MgO–Mg 1.08 Al 1.84 Ti 0.08 O 4 refractories significantly enhanced their corrosion resistance, due to the reduction in porosity and pore diameter, as well as the increase in pore complexity and contact angle. These factors effectively impeded the penetration of RH slag. Additionally, the presence of Mg 1.08 Al 1.84 Ti 0.08 O 4 in contact with RH slag formed a more complex (Mg, Fe)(Al, Ti) 2 O 4 spinel solid solution, which exhibited strong Fe element absorption ability. Thus, this decreased the Fe concentration in the RH slag, resulting in an increase in liquid slag viscosity and enhancing the slag penetration resistance of MgO–Mg 1.08 Al 1.84 Ti 0.08 O 4 refractories. The microstructure of the MgO–Mg 1.08 Al 1.84 Ti 0.08 O 4 refractories featured an isolated distribution of Ca 2 SiO 4 phase, which suggested fewer channels for liquid RH slag to penetrate the refractory materials. According to Factsage 6.2 thermodynamic simulation, the dissolution of Mg 1.08 Al 1.84 Ti 0.08 O 4 into liquid slag was lower compared to the sintered MgAl 2 O 4 , which was advantageous for resisting the dissolution of refractory materials into liquid slag. [ABSTRACT FROM AUTHOR]

The influences of the increasing content of Al 2 O 3 caused by refractory corrosion on the properties and structures of CaO–MgO-(15 wt%-27 wt%)Al 2 O 3 –SiO 2 –TiO 2 –FeO molten slags were studied at high temperature from 1923 K to 1798 K. The viscosity experimental results indicated that the slag viscosity first increased and then reduced with increasing the Al 2 O 3 content in TiO 2 -bearing slags, and the Al 2 O 3 content that reflected the inflection of the viscosity variation was about 21 wt%. From the Raman and NMR spectra analysis, when the Al 2 O 3 content in the TiO 2 -containing slag was lower than 21 wt%, Al 2 O 3 was an acidic oxide which could increase the viscosity, and with the Al 2 O 3 content in slags further increased to 27 wt%, Al 2 O 3 would behave as network modifiers to decrease the slag viscosity. From the XPS results, the amount of O2− decreased first and then raised, while the ratio of O0 and O− increased and then decreased with adding Al 2 O 3 to slags. The changing trend of the oxygens had a good accordance with the variation of slag viscosities. [ABSTRACT FROM AUTHOR]

[Display omitted] • G-FA and F-FA were vitrified together based on their compositional complementarity. • Clean vitrified slag was obtained at 1300 °C without water-washing and any additives. • Cr, Ni, Cu could be recovered as Fe-Cr-Ni-Cu alloy. • FA was efficiently reutilized as three separated phases. The increasing application of municipal solid waste incineration (MSWI) emphasises the need for MSWI fly ash (FA) safe treatment. Based on the compositional complementarity of FA from grate furnaces (G-FA) and fluidised bed incinerators (F-FA), we proposed a co-reduction process to treat G-FA and F-FA together for producing vitrified slag and ferroalloys. The clean vitrified slag and Fe-Cr-Ni-Cu alloy were obtained with the mass ratios of 1:9 ∼ 6:4 (G-FA:F-FA) at 1300℃, which is about 300℃ lower than the conventional G-FA vitrification. The metals Zn, Cd, and Pb were mostly volatilised into the flue gas for potential recovery from the secondary FA. The thermodynamic SiO 2 -Al 2 O 3 -CaO ternary system demonstrated that an optimal mass ratio of the two complementary FA types contributes to the system shifting to the low-temperature melting zone. The co-reduction process of G-FA and F-FA could be a promising option for FA beneficial reutilization with environmental advantages. [ABSTRACT FROM AUTHOR]

Microbially induced carbonate precipitation (MICP) has been used to cure rare earth slags (RES) containing radionuclides (e.g. Th and U) and heavy metals with favorable results. However, the role of microbial extracellular polymeric substances (EPS) in MICP curing RES remains unclear. In this study, the EPS of Lysinibacillus sphaericus K-1 was extracted for the experiments of adsorption, inducing calcium carbonate (CaCO3) precipitation and curing of RES. The role of EPS in in MICP curing RES and stabilizing radionuclides and heavy metals was analyzed by evaluating the concentration and morphological distribution of radionuclides and heavy metals, and the compressive strength of the cured body. The results indicate that the adsorption efficiencies of EPS for Th (IV), U (VI), Cu2+, Pb2+, Zn2+, and Cd2+ were 44.83%, 45.83%, 53.7%, 61.3%, 42.1%, and 77.85%, respectively. The addition of EPS solution resulted in the formation of nanoscale spherical particles on the microorganism surface, which could act as an accumulating skeleton to facilitate the formation of CaCO3. After adding 20 mL of EPS solution during the curing process (Treat group), the maximum unconfined compressive strength (UCS) of the cured body reached 1.922 MPa, which was 12.13% higher than the CK group. The contents of exchangeable Th (IV) and U (VI) in the cured bodies of the Treat group decreased by 3.35% and 4.93%, respectively, compared with the CK group. Therefore, EPS enhances the effect of MICP curing RES and reduces the potential environmental problems that may be caused by radionuclides and heavy metals during the long-term sequestration of RES. Microbially induced carbonate precipitation (MICP) has been used to cure rare earth slags (RES) containing radionuclides (e.g. Th and U) and heavy metals with favorable results. However, the role of microbial extracellular polymeric substances (EPS) in MICP curing RES remains unclear. In this study, the EPS of Lysinibacillus sphaericus K-1 was extracted for the experiments of adsorption, inducing calcium carbonate (CaCO3) precipitation and curing of RES. The role of EPS in in MICP curing RES and stabilizing radionuclides and heavy metals was analyzed by evaluating the concentration and morphological distribution of radionuclides and heavy metals, and the compressive strength of the cured body. The results indicate that the adsorption efficiencies of EPS for Th (IV), U (VI), Cu2+, Pb2+, Zn2+, and Cd2+ were 44.83%, 45.83%, 53.7%, 61.3%, 42.1%, and 77.85%, respectively. The addition of EPS solution resulted in the formation of nanoscale spherical particles on the microorganism surface, which could act as an accumulating skeleton to facilitate the formation of CaCO3. After adding 20 mL of EPS solution during the curing process (Treat group), the maximum unconfined compressive strength (UCS) of the cured body reached 1.922 MPa, which was 12.13% higher than the CK group. The contents of exchangeable Th (IV) and U (VI) in the cured bodies of the Treat group decreased by 3.35% and 4.93%, respectively, compared with the CK group. Therefore, EPS enhances the effect of MICP curing RES and reduces the potential environmental problems that may be caused by radionuclides and heavy metals during the long-term sequestration of RES. [ABSTRACT FROM AUTHOR]

An estimated 30 % (∼11 million metric tons/year) of copper slag is still landfilled globally. Fayalitic copper slags are well-characterized, and they can be recycled into multiple safe end-products. Conversely, the major type of copper slag produced in Europe is lead-rich and warrants a deep understanding of phases present in it, properties, adverse environmental implications, and potential recycling strategies. The objective of this study is to thoroughly investigate such industrial slags by XRF, XRD, Mössbauer spectroscopy, SEM-EDS, novel automated image analysis using Aphelion, hot stage microscopy (HSM) and assess prospects for their valorization. These industrial slags were found to contain 26.1–50.5 wt% PbO, 3.4–5.4 % As 2 O 5 (both hazardous solid wastes), 5.7–42 % CuO (present partly as Cu 2 O, an irritant), 3.2–18.2 % Fe 2 O 3 , 14–15.9 % SiO 2 and oxides of chromium, cobalt (both carcinogenic), zinc and nickel (both toxic to aquatic life). The limitation of Rietveld XRD for glass quantification was overcome by newly-developed automated SEM-image processing which revealed that all three slags consisted of a lead silicate glass (36.3–65.8 vol%). Strikingly, rarely published arsenic- and lead-based compounds like (Ca,Pb) 4 As 2 O 9-x , (Ca,Cu) 2 PbO 4-x and Pb 3 Ca 2 Si 3 O 11 were found when slag's PbO/CuO was 0.6, and Ca 3 As 2 O 8 -Pb 2 SiO 4 formed when PbO/CuO equaled 9. The challenge of toxicity and landfilling can be overcome as these slags have high potential to be used for recovery of copper, cobalt, and lead. Radioactive waste immobilization glasses, gamma-ray shielding concrete and glass-ceramic consumer products may also be prepared from them. HSM revealed that a higher PbO/CuO ratio results in lower melting point and smaller melt contact angle indicating such slag can be useful for manufacturing recycled ceramics but corrosive towards refractories in copper converter. [ABSTRACT FROM AUTHOR]

The present study aims to clarify the role of ball pitch in Al 2 O 3 –SiC–C (ASC) refractory castables and investigate the influence of low temperature treatment on the composition, microstructural evolution, and properties of ASC refractory castables. By utilizing the expansion properties of ball pitch during heating, the castables undergo a low temperature treatment to induce the flow and expansion of ball pitch within the castables. This, in turn, fills the surrounding pores and enhances the physical properties of the castables. The results of this study demonstrate that low-temperature heat treatment of the castables at temperatures at 350 °C significantly improves the hot modulus of rupture, oxidation resistance, and slag resistance after sintering. This improvement is attributed to the optimized microstructure. In comparison to the corresponding samples without low temperature treatment, the high temperature modulus of rupture (HMOR) of the calcined castables treated at 350 °C increases by 33.3%. Additionally, the oxidation index and slag corrosion index after sintering at 1500 °C decrease by 39.6% and 87.31% respectively for the samples low temperature treated at 350 °C, as compared to the samples low temperature treated at 110 °C. This study provides a fresh perspective on the production of ASC castables with exceptional high temperature performance. [ABSTRACT FROM AUTHOR]

The present study illustrates the susceptibility of optimized-quality recycled concrete aggregate (RCA) to supplementary cementitious materials (SCMs), such as silica fume (SF), ground granulated blast slag (GGBS), and mechanically produced recycled fine (M-Fine or MF), in concrete. According to the present research, old interfacial transition zone (OITZ) characteristics may be controlled if RCA is developed in such a way as to reduce mortar adhesion optimally. It may facilitate the penetration of binder particles, strengthening the OITZ even further. A high-quality surface may improve RCA's self-cementing properties, which strengthen the new ITZ (NITZ). The combined effect may yield RCA characteristics equivalent to parent aggregate when interacting with a cement matrix based on SCMs. Substituting the cement with SF (11%), GGBS (14%), and MF (15%) contributes to the compressive strength of recycled aggregate concrete (RAC) up to 11.61% via strengthening the OITZ. SF and GGBS further enhance RAC tensile strength in a similar way to how they enhance natural aggregate concrete (NAC) tensile strength. The elastic modulus (MOE), fracture energy, and durability characteristics of RAC with SF and GGBS are significantly improved. RAC with MF (15%) shows compressive and tensile strength comparable to RAC with GGBS (14%) with marginal reductions in flexural strength. In comparison to RAC, RAC with MF has a 2.9% lower MOE. RAC-MF has 1.82% higher fracture energy than RAC. RAC-SF, RAC-GGBS, and RAC-MF have significantly reduced water absorption and water absorption rate (sorptivity) than RAC. There is a strong correlation between the compressive strength of RAC, RAC-SF, RAC-GGBS, and RAC-MF, and their UPV with R2=0.92. The sorptivity and electrical resistivity are also correlated with R2=0.86. SEM images show uniform and dense microstructure and EDS analyses shows Si-rich C-S-H gel formation, resulting in superior mechanical and durability properties in RAC with SCM compared to RAC. Practical Applications: About 20% to 30% of recycled fines (M-Fines) below 150 μm are generated during RCA processing from construction and demolition waste. In addition, M-Fines are also generated during the removal of the mortar attached to the RCA. Thus, M-Fines as by-products of mechanical processing of RCA could be used as cementitious materials. Despite M-Fine's low reactivity compared to SF, it may produce strength and durability characteristics comparable to other conventional supplementary cementitious materials like GGBS. In structural concrete, optimized-quality recycled concrete aggregates with supplementary cementitious materials, including M-Fines, can be used. In this way, it may be possible to promote construction and demolition waste recycling operations. Moreover, the effectiveness of SF and GGBS with RCA, as well as the performance of RAC-MF, may encourage the use of RAC as structural concretes and M-Fines as supplementary cementitious materials. [ABSTRACT FROM AUTHOR]

Fly ash (FA) and granulated blast furnace slag (GBFS) were used as a precursor for geopolymerization to develop a low-carbon pavement base construction material. Based on the orthogonal test method, three levels were set separately for the L9 (34) test considering the proportion of FA (raw fly ash to grained fly ash), ratio of sodium hydroxide to liquid alkaline activator (LAA), and proportion of GBFS mixed with FA and solid–liquid ratio [(FA + GBFS): LAA] as factors influencing the geopolymer. The influence of these factors on the unconfined compressive strength (UCS) of soil stabilized by geopolymer was studied. The optimal combinations of levels and factors were determined. The UCS with these ratios combined was 5.1 MPa. According to the above compositions, the mechanical (UCS, splitting tensile strength, and flexural tensile strength) and durability (drying shrinkage, water stability, freezing and thawing resistance, and wet–dry cycle) properties of soil samples stabilized using the aforementioned geopolymer were investigated. Moreover, scanning electron microscopy (SEM) and x-ray diffraction (XRD) analysis were performed to determine the effect of the change in hydration silicate gel in the UCS development. According to the SEM and XRD test results, hydrated silicate gels exist in the sample, filling the pores of the soil, making the soil more compact, bonding the soil particles, and enhancing the engineering performance of the soil. This study enables waste material utilization as a replacement and partially reactive material in pavement applications. [ABSTRACT FROM AUTHOR]

Colored asphalt mixtures have recently found extensive applications in roads and public spaces due to their contribution to traffic management as well as aesthetics and landscaping. The development of durable colored asphalts using various materials has been a hot research topic in recent years. Colored asphalt can be developed through the durable colored slurry seal mixture (CSSM) technology. The desired quality of CSSM requires particular attention to the mechanical performance and resistance against crack propagation due to temperature variations and traffic loads. This research aimed at investigating the effect of steel slag (SS) aggregate compared with natural aggregate (NA) on the fracture behavior and performance of CSSM in five different mixtures: NA100% (control sample), SS10%+NA90% , SS20%+NA80% , SS30%+NA70% , and SS40%+NA60%. The performance of CSSM was evaluated using an edge-notched disk bend (ENDB) specimen fracture test at three different temperatures (0°C, −10°C , and −20°C). Additionally, cohesion test, wet track abrasion test, loaded wheel test (LWT)-displacement and LWT-sand adhesion were carried out to further examine the samples. Comparison of the fracture behavior of colored mixtures revealed that the SS40%+NA60% mixture outperformed other mixtures. The results of other performance tests showed that the unique characteristics of SS40%+NA60% mixture improved CSSM performance against vertical displacements, bleeding, cohesion, and moisture sensitivity by approximately 40.2%, 4 7.3%, 28.6%, and 52.7%, respectively. This comprehensive assessment offers valuable insights into the effectiveness of SS as a proper alternative to NA in CSSMs. [ABSTRACT FROM AUTHOR]

This study prepared modified alkali-activated slag repair materials by incorporating an ethylene-vinyl acetate copolymer emulsion (EVA). Sulfate attack tests, shrinkage tests, scanning electron microscopy, and mercury intrusion porosimetry tests were conducted to examine the durability and microstructural features of the alkali-activated slag repair materials. The experimental results demonstrated that adding EVA can enhance the shrinkage and strength of alkali-activated slag mortar, but that the materials exhibit poor resistance to sulfate attack. Optimizing the ratio design can yield alkali-activated cementitious materials with high strength, good durability, high bonding strength, and low shrinkage. This can reduce brittleness and increase the shrinkage rate of the material's defects, which has significant implications for subsequent fracture repair. The image of the microstructure showed that the section of alkali-activated slag paste is smooth and exhibits polymer emulsion filling gaps in the amorphous cementitious material. A connection between fibrous filaments on the cross section of the matrix crack enhances the strength of the material. The proportion of microcracks is increased and material strength is decreased after sulfate attack. [ABSTRACT FROM AUTHOR]

Below 5 °C, Portland cement (PC) experiences delayed hydration, slowing strength development, making it unsuitable for winter. Alkali-activated slag (AAS) emerges as a viable alternative with continuous hydration in low-temperature conditions. The effect of the activator nature on the performance of AAS cured at normal temperatures is well known, but further studies are required for low-temperature conditions. This study investigates the synergistic impact of activator modulus (1.2 and 1.5), alkali dosage (5, 7, and 9%), and PC substitution rates (0, 10, and 20%), on low-temperature cured AAS properties. Eighteen mixtures were prepared and cured at 2 °C. Compression and ultrasonic pulse velocity tests were conducted after 7, 28, and 90 days. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy analyses were performed to examine the microstructure of the samples. Elevating alkali dosage enhanced early age strength but resulted in a drop in 90-day strength. Simultaneous increases in modulus and PC substitution rate reduced strength due to shrinkage-induced crack formation. Optimal mixture design options included using 10% PC in the 1.2 modulus and omitting PC when the 1.5 modulus was selected. Despite low temperatures, the use of PC significantly accelerated the setting time. Altering modulus and alkali dosage caused a considerable change in the intensity of the peaks in the FTIR spectrum. The findings indicate that AAS shows promise when adjusting the mixture design for temperatures below 5 °C, which are unfavorable for the hydration of PC. [ABSTRACT FROM AUTHOR]

Alkali-activated slag recycled coarse aggregate concrete (AAS-RAC) is a novel type of green building material with significant growth potential, utilizing waste slag and construction waste effectively. However, its large shrinkage and poor toughness limit its further utilization. Adding fiber is the crucial way to limit its shrinkage. Therefore, the effects of fiber type and content on the shrinkage performance of AAS-RAC were systematically studied. The results show that the incorporation of recycled aggregate increases the shrinkage of AAS-RAC, and AAS-RAC of full recycled aggregate is 59% higher than that of undoped aggregate. The addition of steel fiber, polypropylene fiber and basalt fiber can effectively reduce the shrinkage of AAS-RAC. Among them, steel fiber has the best inhibition effect, and 0.6% steel fiber can reduce the shrinkage of AAS-RAC by 30.6%. The AAS-RAC shrinkage model considering the influence of fiber content and recycled aggregate is established. The research results provide an effective way to reduce the shrinkage of AAS-RAC. [ABSTRACT FROM AUTHOR]

Tunnel waste constitutes a prevalent by‐product of highway construction in high‐altitude mountainous and hilly regions. Sulphide minerals exhibit a unique distribution pattern within the alpine hills. Consequently, tunnel excavation can disrupt the stability of these sulphide minerals, rendering the tunnel waste susceptible to generating secondary environmental hazards during stockpiling. This research delves into the migration and transformation dynamics of potential environmental pollutants in tunnel waste through geoenvironmental simulation techniques. Controlled variables were employed to simulate various conditions, including surface illumination, internal anaerobiosis, water content and aerobic environments. The study's findings indicate that the presence of pyrite in the waste stream primarily drives the secondary contamination of the tunnel waste. Pyrite within the slag tends to react and form sulphuric acid in the stockpile environment, thus creating an acidic milieu that exacerbates the release of existing contaminants. The emergence of an anaerobic environment and a photocatalytic system composed of Fe/Ti substances in the waste stream serves to further accelerate pollutant release. This study thoroughly investigates the primary causes of environmental pollution during the stockpiling of tunnel slag and assesses the potential environmental impact scenarios. The outcomes of this research offer substantial theoretical and empirical support for the management of slag generated during the tunnel construction process. [ABSTRACT FROM AUTHOR]

To explore the reaction mechanism of sludge, slag, lime, and fly ash in high temperature environments, the unconfined compressive strength (UCS) test was hereby implemented to study the effect on curing age, curing temperature, slag content and fly ash content about the strength of sludge. Scanning electron microscopy (SEM) was used to observe the microscopic composition of the substance, and X-ray diffraction (XRD) was used to analyze the mineral composition at the micro level to further disclose its reinforcement mechanism. The experimental results demonstrate the difference in the strength measured by different dosage of curing agent, and results indicate that the strength of high temperature curing sample was obviously higher than that of low temperature curing sample. When the curing temperature rises, the pozzolanic reaction and hydration reaction between materials are accelerated, and a certain amount of gel products are produced, playing a precipitation and bonding role between particles. The 28 days and 90 days strengths of the sludge samples with 20% fly ash and 80% slag dosing at 40°C were 1139 KPa and 1194 KPa, which were 1.4 and 1.1 times of that of pure cement solidified sludge. At 60°C, the strength of 14 days, 28 days and 90 days were 802 KPa, 1298 KPa and 1363 KPa, which were 1.1, 1.5 and 1.3 times of that of pure cement solidified sludge. Under the influence of an alkaline environment, the silicon-aluminum grid structure was interconnected into a denser network structure, and the compressive strength of lime-activated fly ash-slag was thus continuously enhanced. Affected by the high temperature, lime-activated fly ash-slag solidified sludge could significantly improve the middle and late strength of the sample. The research showed that the new solidification material can replace partly the concrete curing agent, thereby alleviating the carbon emission and environmental pollution problems arising from cement solidified sludge. [ABSTRACT FROM AUTHOR]

This article reports on development of an adaptive framework for predicting the erosion performance of polymer composites using certain statistical and machine learning (ML) models. For this, ramie‐epoxy composites reinforced with variations (0–30 wt%) of sponge iron slag (an iron industry waste) are considered. The composites are fabricated and then subjected to high temperature solid particle erosion wear trials following Taguchi's L27 orthogonal array. The effects of different control factors on the erosion rate in an interactive environment are appraised by analysis of variance (ANOVA) which reveals the filler content as the most significant factor contributing 66.21%, followed by impact velocity (22.86%) and impingement angle (2.28%). A regression model based on the input–output parameters obtained from experimentation is constructed for prediction of erosion rate. Further, four predictive models using different machine learning algorithms are also proposed to predict the erosion rate of the composites. The feasibility and performance of each ML model is assessed using appropriate performance metrics. Among all the models, the gradient boosting machine model is found to be the most reliable model exhibiting the highest prediction accuracy and least errors. Highlights: Development of novel class of composites reinforced with sponge iron slag.Database creation based on erosion wear experimentation on the composites.Data‐driven modeling for prediction of erosion rates using machine learning.Comparison of performance of different models and identifying the best one. [ABSTRACT FROM AUTHOR]

Brine magnesia and fused Al 2 O 3 –ZrO 2 powder were used as raw material to prepare MgO–Al 2 O 3 –ZrO 2 (MAZ) refractory brick which was sintered at 1690 °C for 8 h in a tunnel kiln. Its resistance to slag corrosion of non-ferrous metallurgy was investigated. The phase and microstructure of the samples before and after corrosion were characterized by XRD, SEM and EDS. The results show that MAZ ternary metastable phase was formed during sintering, which then decomposes to finely dispersed MgO, MgAl 2 O 4 , and ZrO 2. Thus, highly uniform distribution of ultra-fine MgAl 2 O 4 and ZrO 2 in the matrix was achieved. The non-ferrous metallurgical slag is mainly composed of FeO and SiO 2. At high temperatures, when the material is subjected to slag corrosion, both (Mg, Fe)Al 2 O 4 and 2MgO·SiO 2 with high-temperature melt point were formed in the corrosion layer, effectively preventing further infiltration and corrosion of MAZ samples by slag. A model for the formation process of high dispersion of MAZ was explained, and a model for the corrosion mechanism between non-ferrous metallurgical slag and MAZ samples was established. [ABSTRACT FROM AUTHOR]

Froth flotation, a prevalent technique for the separation of fine materials, is employed in the decarburization process of coal gasification fine slag (CGFS). This process is known to consume significant quantities of reagents. This study investigates the pronounced variance in collector consumption during the flotation decarbonization of two distinct CGFS samples, where a tenfold difference was observed when the tailings ash content surpassed 95%. A comprehensive set of analyses, including XPS, BET, SEM, wettability tests, LF-NMR and IGC-SEA, was conducted on the residual charcoal from CGFS to elucidate the mechanism behind reagent consumption. The findings reveal that the reagent’s ability to alter the surface hydrophobicity of residual charcoal is contingent upon the adsorption saturation of micropores and transition pores. Furthermore, variations in porosity and surface energy significantly impact collector consumption, independent of differences in the type and quantity of oxygen-containing functional groups. This investigation aims to provide a theoretical framework for reducing the dosage of reagents in the flotation decarburization of CGFS. [ABSTRACT FROM AUTHOR]

[Display omitted] • Recycling aluminium in a rotary furnace saves great environmental impacts. • Valorising the salt slag instead of landfilling improves LCA indicators by 5–25 %. • The discounted impacts from the secondary aluminium dominate the LCA results. • Other benefits are recovery of NMCs, ammonium sulphate and landfill prevention. • Metal Yield assumptions from 20 to 95 % change the GWP from −3.5 to −17 t CO 2 eq. Recycling aluminium in a rotary furnace with salt-fluxes allows recovering valuable alloys from hard-to-recycle waste/side-streams such as packaging, dross and incinerator bottom ash. However, this recycling route generates large amounts of salt-slag/salt-cake hazardous wastes which can pose critical environmental risks if landfilled. To tackle this issue, the metallurgical industry has developed processes to valorise the salt-slag residues into recyclable salts and aluminium concentrates, while producing by-products such as ammonium sulphate and non-metallic compounds (NMCs), with applications in the construction or chemical industries. This study aims to assess through LCA the environmental impacts of recycling aluminium in rotary furnaces for both salt-slag management routes: valorisation or landfill. It was found that this recycling process brings forth considerable net environmental profits, which increase for all the considered impact categories if the salt-slag is valorised. The main benefits arise from the production of secondary cast aluminium alloys, which is not unexpected due to the high energy intensity of aluminium primary production. However, the LCA results also identify other hotspots which play a significant role, and which should be considered for the optimisation of the process based on its environmental performance, such as the production of by-products, the consumption of energy/fuels and the avoidance of landfilling waste. Additionally, the assessment shows that the indicators for mineral resource scarcity, human carcinogenic toxicity and terrestrial ecotoxicity are particularly benefited by the salt-slag valorisation. Finally, a sensitivity analysis illustrates the criticality of the metal yield assumptions when calculating the global warming potential of aluminium recycling routes. [ABSTRACT FROM AUTHOR]

To elucidate the distribution law of the multiphase coupling slag discharge flow field in gas-lift reverse circulation during drilling shaft sinking, a numerical analysis model of gas–liquid–solid multiphase coupling slag discharge was established by CFD–DEM (Coupling of computational fluid dynamics and discrete element method) method, taking the drilling of North Wind well in Taohutu Coal Mine as an example. This model presented the distribution of the multiphase flow field in the slag discharge pipe and at the bottom hole, and was validated through experimentation and theoretical analysis. Finally, the impact of factors, including bit rotation speed, gas injection rate, air duct submergence ratio, and mud viscosity on the slag discharge flow field was clarified. The results indicated that the migration of rock slag at the bottom of the well was characterized by "slip, convergence, suspension, adsorption, and lifting". The slag flow in the discharge pipe exhibited the states of "high density, low flow rate" and "low density, high flow rate", respectively. The multiphase fluid flow patterns in the well bottom and slag discharge pipe were horizontal and axial flows, respectively. The model test of the gas lift reversed circulation slag discharge and the theoretical model of the bottom hole fluid velocity distribution confirmed the accuracy of the multiphase coupling slag discharge flow field distribution model. The rotation speed of the drill bit had the most significant impact on the bottom hole flow field. Increasing the rotation speed of the drill bit can significantly enhance the tangential velocity of the bottom hole fluid, increase the pressure difference between the bottom hole and annular mud column, and improve the adsorption capacity of the slag suction port. These findings can provide valuable insights for gas lift reverse circulation well washing in western drilling shaft sinking. [ABSTRACT FROM AUTHOR]

Hastinapur is one of the prominent painted grey ware archaeological sites in the Ganga Valley. In the present communication, we report the results of the metallurgical analysis of the excavated slag samples from the site. The existence of a large number of iron objects for this site can be dated between c. 6th century BCE and c. 16th century CE, with early iron from the 8th century BCE. The morphological, microstructural and elemental studies of the excavated slag indicate a high amount of carbon in iron, indicating crucible carburization activities at this site. In addition, the presence of niobium, cobalt, etc. in the slag indicates the usage of non-traditional iron ores in the primary ironmaking stage. [ABSTRACT FROM AUTHOR]

In order to overcome the serious corrosion problem of furnace hearth refractory materials for smelting reduction ironmaking, the Cr 2 O 3 –Al 2 O 3 –MgO–ZrO 2 refractories were synthesized, and the phase component, microstructure, mechanical characteristics, and slag erosion behavior of composite refractories were investigated and evaluated. The results indicate that the composite refractories mainly consist of Mg(Al, Cr) 2 O 4 spinel phase, (Al, Cr) 2 O 3 solid solution and ZrO 2. The content of Mg (Al, Cr) 2 O 4 spinel significantly increases with the increasing MgO content, while the content of (Al, Cr) 2 O 3 obviously decreases. Furthermore, the comprehensive mechanical properties of the MgO modified composite refractories can be obviously enhanced by increasing the MgO content, and sample S4 presents the best mechanical characteristics when the MgO addition is 10 wt%. The corresponding hardness, compressive strength and bending strength are 14.22 GPa, 267.14 MPa and 80.0 MPa, respectively. This is mainly because the formation of Mg(Al, Cr) 2 O 4 significantly improves the densification of composite refractories, and a large number of high-strength Mg (Al, Cr) 2 O 4 spinel "bridge" formed between the large-sized (Al, Cr) 2 O 3 grains. The erosion test results indicate that increasing the MgO content can significantly improve the slag infiltration resistance of composite refractories, because the formation of Mg (Al, Cr) 2 O 4 spinel layer significantly improves the densification of MgO reinforced composite refractories. Although the slag corrosion resistance of Mg(Al, Cr) 2 O 4 is lower than that of (Al, Cr) 2 O 3 , the Cr 2 O 3 –Al 2 O 3 –MgO–ZrO 2 refractories still presents good erosion resistance, permeability resistance, and excellent mechanical characteristics. [ABSTRACT FROM AUTHOR]

In this paper, results of research on the reactivities of selected biomass types considering their application in pyrometallurgical processes of metal production are presented. Walnut shells, sunflower husk pellets and spent coffee grounds were selected as biomass materials. Their use as potential reducers in the process of metallurgical slag decopperisation is an innovative approach to this subject. The thermogravimetric findings show that all three tested biomass types are classified as highly reactive. The time to reach maximum reactivity ranges from 1.5 to 3 min and, the lowest value is recorded for the sample of spent coffee grounds. The sample hold time of two hours enables copper content reduction to approx. 1 wt% for practically all the reducers tested. A longer duration of liquid slag contact with the reducer results in a decreased copper content in the slag to a value below 1 wt%. Copper concentrations of 0.5 wt% and lower are observed with a hold time of 4 h. The preliminary results indicate that there is great potential for the use of this type of material in non-ferrous metallurgy, which may translate into replacing fossil raw materials and thus introducing the principles of a sustainable process in this case of metal production. [ABSTRACT FROM AUTHOR]

Cement-based cementitious materials occupy a central position in the construction industry, but the problem of high carbon dioxide(CO2) emissions from cement production has attracted global attention. To meet this challenge, finding low-carbon alternative materials has become a top priority in the research of new building materials. At the same time, the problem of large amounts of lithium slag piling up needs to be solved, and resource utilization has become its potential way out. In this study, the volcanic ash activity of lithium slag was activated by composite activation means of high-temperature calcination and sodium silicate, and it was used as an alternative mix to cement. The Box–Behnken design and response surface method (BBD-RSM) was utilized to optimize the ratio of activated lithium slag composite cement-based cementitious materials, and high-performance new solid waste cementitious materials were prepared. The results show that activated lithium slag composite cementitious materials activated lithium slag exhibit excellent performance when activated lithium slag mass fraction is 7.3%, the sodium silicate dosage is 8.8%, and water–solid ratio is 0.6:1. The composite cementitious material under this ratio shows excellent performance, with fluidity 235.69 mm, gelation time 73.54 s, water evolution rate 1.123%, 3d and 28d compressive strengths, respectively, are 11.54 MPa and 22.9 MPa. Compared with ordinary Portland-cement-based cementing materials, the uniaxial compressive strength, modulus of elasticity, and tensile strength at break of activated lithium slag cementitious material solidified body were increased by 34.33%, 36.43%, and 34.98%, and the compressive deformation and tensile deformation were enhanced by 37.78% and 40%. This study not only provides a theoretical basis and experimental foundation for the preparation of new solid waste cementitious materials, but also provides a new solution for the reinforcement of crushed rock bodies in engineering practice, which is of great significance for promoting the low-carbon development of the construction industry. [ABSTRACT FROM AUTHOR]

In this paper, the possibility of retreated lithium slag (RTLS) with a high content of alkali, sulfate and fluoride as a partial replacement for fly ash (FA) to produce autoclaved aerated concrete (AAC) was investigated. The influence of the RTLS dosage on the AAC performance were examined. The composition and microstructure of hydrates as well as the microstructure of the RTLS-FA-based AAC compositions were determined by XRD, FTIR, TG-DSC and SEM. The results illustrated that the incorporation of RTLS changed the crystal structure and the microstructure of the tobermorite. With increased RTLS contents, the morphology of tobermorite was changed, and the grass-like tobermorite gradually transformed into network-like tobermorite. The newly formed tobermorite improved the mechanical performance of the AAC. Compared with the RTLS10, the content of tobermorite in the RTLS30 increased by 8.6%. [ABSTRACT FROM AUTHOR]

This study investigated the influences of ultrafine fly ash (UFA) and ultrafine slag powder (USL) on the compressive strengths, autogenous shrinkage, phase assemblage, and microstructure of magnesium potassium phosphate cement (MKPC). The findings indicate that the aluminosilicate fractions present in both ultrafine fly ash and ultrafine slag participate in the acid–base reaction of the MKPC system, resulting in a preferential formation of irregularly crystalline struvite-K incorporating Al and Si elements or amorphous aluminosilicate phosphate products. UFA addition mitigates early age autogenous shrinkage in MKPC-based materials, whereas USL exacerbates this shrinkage. In terms of the sustained mechanical strength development of the MKPC system, ultrafine fly ash is preferred over ultrafine slag powder. MKPC pastes with ultrafine fly ash show greater compressive strength compared to those with ultrafine slag powder at 180 days due to denser interfaces between the ultrafine fly ash particles and hydration products like struvite-K. The incorporation of 30 wt% ultrafine fly ash enhances compressive strengths across all testing ages. [ABSTRACT FROM AUTHOR]

The static compaction technique emphasizes the reduced activator dosage required to develop geopolymers. Therefore, it is crucial to comprehend the optimal alkaline activator concentration for blending low-calcium precursor (fly ash) with high-calcium precursor (GGBS) to produce geopolymer blocks. This work was designed to optimize structural blocks' compressive strength and durability. In experimentation, fly ash (FA) and slag (GGBS) proportions were initially investigated under NaOH solution with varying molarity (8–12) and curing conditions to develop a load-bearing structural block. Subsequently, the durability of the optimized block was evaluated over 56 days through subjection to sulfate and acidic solutions, with efflorescence monitored over the same period. The results reveal that the structural block comprised of 100% FA exhibits the highest compressive strength and lowest bulk density. Conversely, the block incorporating 25% slag that underwent hot curing demonstrates a remarkable 305% strength increase compared to ambient curing. Considering the physico-mechanical performance, the 100% FA block was chosen for durability investigation. The findings indicate a substantial strength loss exceeding 40% after exposure to sulfate and acidic environments over 56 days, coupled with pronounced efflorescence. Catastrophic failure occurs in all cases due to significant strength deterioration. The FTIR spectrum revealed the shifting of the wavenumber to a higher value and verified the depolymerization and leaching of alumina under acidic exposure. However, the developed geopolymer blocks demonstrate superior sustainability and feasibility compared to conventional fired clay bricks and cement-based FA bricks. Despite slightly higher costs, these blocks exhibit greater strength than their counterparts after enduring severe exposures. [ABSTRACT FROM AUTHOR]

Slag and fly ash (FA) are mostly used as precursors for the production of alkali-activated materials (AAMs). FA is the waste discharged by power plants, while slag and steel slag (SS) both belong to the iron and steel industry. The effects of SS and FA on the strength, microstructure, and volume stability of alkali-activated slag (AAS) materials with different water glass modulus (Ms) values were comparatively investigated. The results show that adding SS or FA decreases the compressive strength of AAS mortar, and the reduction effect of SS is more obvious at high Ms. SS or FA reduce the non-evaporable water content (Wn) of AAS paste. However, SS increases the long-term Wn of AAS paste at low Ms. The cumulative pore volume and porosity increase after adding SS or FA, especially after adding FA. The hydration products are mainly reticular C-(A)-S-H gels. Adding SS increases the Ca/Si ratio of C-(A)-S-H gel but decreases the Al/Si ratio. However, by mixing FA, the Ca/Si ratio is reduced and the Al/Si ratio is almost unchanged. The incorporation of SS or FA reduces the drying shrinkage of AAS mortar, especially when SS is added. Increasing Ms increases the compressive strength and improves the pore structure, and it significantly increases the drying shrinkage of all samples. This study provides theoretical guidance for the application of steel slag in the alkali-activated slag material. [ABSTRACT FROM AUTHOR]

Zinc-copper alloy ash contains Cu, Zn, Al, Ni, Sn, Pb and other non-ferrous metals. In this paper, t he effective treatment of zmccopper ash in different particle size ranges ss realized by screening. The effects of sulfuric acid content, temperature, time, i iquid-soiid ratio, rotation speed, oxidant and roasting conditions on the selective eaching of different meta! were investigated. The resutts show that the zinccopper ash with partid size kss than 0. 15 mm ss caHned at 750 °C for 3 hours, and then leached at 85 °C, s uHunc acid content of 1. 2 g/g ash, iiquid-to-solid ratio of 5/1, sirring speed of 400 r/min, H202 0. 075 mL/g ash for 5 h. The removal rate of zinc ss 93. 40%, and the removal rate of copper ss 0. 23%. Compared with the initia1 copper ash, the ZnO n the copper ash after roasting and leaching ss greatly reduced. The leaching residue was mixed with copper slag with a particle size of 0. 15-0. 25 mm, roasted at 750 C for 4 hours, and then washed wI 2 mol/L suHurtc acid solution for 5 hours and washed wI water under the same condiions. The steps can remove a !arge number of impurtty metal e!ements inthe copper slag. The phase composition of the copper slag after pickling is mainly Cu, and the proportion of Cu elements reach 92. 52%. [ABSTRACT FROM AUTHOR]

It has become a general developing trend to resource recyciing lead-contammg soiid waste,such as lead-silver leaching residues by kad smelting. However, due to the obvious difference of raw material structure, the conventional direct reduction control theory of ligh--ead slag is not suitable for that of the mixed lead-si1ver eaching resddues and lead concentrates. To investigate the stag formation characteristics and reaction kinetics of the direct reduction process for recyciing lead-si1ver stag leaching resddues^n the basss of the occurrence state analysis of raw materiais and thermodynamic caiculation, combined subsequent reduction experiment.. The resuits show that both the early and kte stages of reduction (>30 min) are controled by interfacia1 reactions, and the 20 -- 30 min of reduction controled by external diffuson. Therefore, the reduction reaction efficiency can be enhanced by Increasing the reaction interface and reducing the viscosity of stag. As the reduction process proceeds, the !ead-containing phase in the slag vansshed off, the zinc mejijite and iron-zinc spinel phases gradually increased, the sijicate structure of stag ss changed from simple SiO" to Si2O7, and the meiiing temperature and viscosity of the stag Increase accordingly. The dreci smeiiing process for treating !ead-silver eaching residues mixed with !ead concentrates can meet the requrrements of reduction smeiiing production though controlling reduction smeiing stag with FeO/SiO2=1. 6,CaO/SiO2 = 0. 6, and ZnO ) 20 w.. %. [ABSTRACT FROM AUTHOR]

Addressing increased damage to hot metal ladle refractory linings from FeO x of scrap steel, Al 2 O 3 –SiC–C refractories were prepared at 1400 °C with corundum, SiC, graphite as raw materials, and fused magnesia as additives. The impacts of additives on phase changes, microstructure, and properties were researched. The findings indicate that the oxide layer of Al 2 O 3 –SiC–C refractories with in-situ generated MgAl 2 O 4 is denser than that of the blank sample after the oxidation test. This denser layer effectively inhibits the diffusion of O 2 , leading to a significant enhancement in oxidation resistance. After the corrosion test, it was observed that a part of Al 2 O 3 was wrapped by Mg(Al, Fe) 2 O 4 at the interface between the sample with generated in-situ MgAl 2 O 4 and the slag. This structure can ensure the integrity of the material structure and fix some Fe2+ to weaken its corrosion to the refractory components, and its corrosion resistance is higher than that of the blank sample. [ABSTRACT FROM AUTHOR]

During the blast furnace (BF) smelting process, the viscosity of BF slag affects greatly the quality of molten iron, slag-iron separation, gas flow distribution, etc. After discharged from BF, the crystallization of molten slag at low cooling rate will decrease the glass content and hydration activity of slag, which occurs more easily in the tempting heat recover system of molten slag for energy saving and emission reduction. The glassy slag at quite cooling rate is the valuable resource to replace virgin raw material to conserve the natural resource for producing the value-added materials, which facilitates the circular economy and sustainable development. This paper firstly describes the generation of BF slag, and discusses the research methods of viscosity-structure of the slag and detailed effects of basic oxides, acidic oxides and amphoteric oxides. Then, the characterization methods for crystallization of slag, determination of critical cooling rate, precipitated phases and the effect of chemical components are summarized. With regard to the preparation of glass-ceramics from BF slag, the effects of heat treatment, nucleation agent, addition amount of the slag and main chemical components are expounded. At last, the future challenges and attentions on the viscosity, crystallization and glass-ceramics preparation of BF slag are scrutinized. [ABSTRACT FROM AUTHOR]

In recent years, researchers have prepared glass-ceramics using a mixture of multiple solid waste materials, which is an effective and resourceful way to use and store solid waste. However, solid waste usually contains multiple heavy metals, which presents challenges during the mixing and co-solidification processes. In this study, high-performance glass-ceramics with low leaching were prepared from blast furnace slag (BFS). The synergistic curing mechanism of BFS glass-ceramics for heavy metals Cr, Mn, Cu, Zn, Ni, and Co was investigated in detail, as well as the migration pattern and storage state of heavy metals under different heat treatment stages and different Cr contents. The results show that the increases in temperature and Cr 2 O 3 content contribute to the incorporation of heavy metals into the crystal lattice and promote crystal growth. Excessive crystallization of spinel causes aggregation, which further curtails the leaching of heavy metals. The leaching concentration of heavy metals mainly depends on the heavy metal content in the glass network and the degree of network polymerization. Thus, spinel acts as a crystal core for the solidification of heavy metals, while augite and glass phases act as a double barrier to physically encapsulate them, which is effective for the storage of a wide range of heavy metals. Furthermore, the physical and chemical properties of BFS glass-ceramics are consistent with the Chinese industry standard "Glass-ceramics plate for industrial application" (JC/T 2097-2011). This study provides important theoretical support for the synergistic solidification of multiple heavy metals in glass-ceramics, as well as insights into the preparation of glass-ceramics by mixing BFS with other solid wastes. [Display omitted] [ABSTRACT FROM AUTHOR]

Ceramic dissolution within silicate melts is often caused by Marangoni convection arising from surface tension gradients, unless it is counteracted by forced convection, which typically occurs beyond a specific critical Reynolds number ( R e c). This study presents a method for determining the R e c required to suppress Marangoni convection at the alumina (Al 2 O 3)/slag/air triple point. This approach utilizes a modified finger test device equipped with a high-resolution laser for dimensional measurement, allowing accurate determination of mass flux densities from the grove and mantle separately. Subsequently, we examined the dissolution of Al 2 O 3 fine ceramics in a quaternary silicate melt of calcium oxide (CaO)–Al 2 O 3 –silicon dioxide (SiO 2)–MgO (or magnesium oxide), featuring a CaO/SiO 2 weight ratio of 0.65. The experiments were conducted at 1550 °C for speeds of 0, 50, 100, and 200 rpm. The findings revealed a critical rotational speed of 127 rpm for Al 2 O 3 -dissolution in this silicate slag at 1550 °C using the aforementioned device, corresponding to an R e c of 6.46. These results contribute to a deeper understanding of the factors influencing ceramic dissolution in silicate melts and offer valuable insights for materials and process engineering applications. [ABSTRACT FROM AUTHOR]

A pyro-hydrometallurgical process is proposed in this study for the selective arsenic removal and the Pb and Sb recovery from lead softening slag, which incorporates NaOH roasting followed by water leaching, carbothermic reduction, and HNO3 leaching as process steps. Lead softening slag, containing 63.9 wt% Pb, 17.7 wt% Sb, and 4.4 wt% As, is first roasted with NaOH at 400°C, followed by water leaching at room temperature. The effect of the roasting temperature and NaOH dosage is investigated with regard to the removal yield of As, Pb, and Sb. The arsenic-free slag is reduced with carbon for Pb recovery as the antimonial lead. The reduction temperature and carbon dosage are optimized by applying FactSage modeling and performing experimental tests for selective Pb recovery. The residual slag is leached with HNO3 solution for the further removal of Pb and enrichment of Sb. The chemical and phase composition of the final leaching residue is determined to assess the possibility of using it as a feedstock for antimony trioxide production. The proposed process flowsheet enables the recovery of Pb and Sb as antimonial lead and antimony trioxide, respectively. [ABSTRACT FROM AUTHOR]

Unalloyed copper objects were produced in the Chalcolithic Southern Levant in a two‐step process. Copper ore was smelted in pit furnaces, and the mechanically extracted copper prills melt in crucibles and cast into objects. However, the air supply remained unknown, and practical considerations shed doubt on the validity of some of the reconstructed practices. To refine the reconstruction, the metallurgical material from Abu Matar was reassessed. Most importantly, several previously unreported fragments suggest the use of bellows and covering the furnace with large pottery fragments. Our results provide probably the earliest evidence for the use of bellows. [ABSTRACT FROM AUTHOR]

Alkali‐activated materials can be formed by alkali‐activation of Fe‐rich non‐ferrous metallurgical slags (AA‐NFMS). To study NFMS in AA‐NFMS systematically, five NFMS were synthesized, with different CaO (6–16 wt%), Al2O3 (7–11 wt%), and MgO (0–4 wt%) contents, while keeping the same FeOx/SiO2 molar ratio. The effect of slag chemistry and the alkali ions (Na+/K+ = 0, 0.5, and 1) in alkali‐activating solution on the reaction kinetics, compressive strength (3, 7, and 28 days), and pore structure of AA‐NFMS was investigated. The reactivity up to 3 days was evaluated via isothermal calorimetry, and the pore structure was analyzed via mercury intrusion porosimetry. Higher Al/Si in the slag showed higher reactivity, higher compressive strength, and lower total porosity of the AA‐NFMS. Higher Ca/Si yielded lower cumulative heat after 3 days and decreased early compressive strength but higher strength after 28 days of curing. Ca replacement by Mg led to faster reaction kinetics but inferior mechanical properties and increased porosity. Increased K+ concentration in the activator resulted in higher reactivity and compressive strength despite the higher total porosity. Empirical model fitting using JMP software revealed that K+/(N++ K+) in the activator, Ca/Si, and (Ca+Mg)/Si in NFMS are significant factors that affect the strength of AA‐NFMS. [ABSTRACT FROM AUTHOR]

We report the effects of sodium phosphate dodecahydrate (Na3PO4·12H2O) as a foam stabilizer on the crystalline phases, microstructure, and properties of foamed glass–ceramics derived from solid industrial wastes. Our findings reveal that Na3PO4·12H2O acts as a pore structure stabilizer, enhancing pore uniformity by releasing P2O5 during decomposition. Additionally, it lowers the softening temperature and viscosity by supplying Na2O. X‐ray diffraction analysis demonstrates that Na3PO4·12H2O does not alter the primary crystal types but does influence the crystallinity and morphology. With an increase in Na3PO4·12H2O content, the porosity and water absorption improve, but the bulk density, thermal conductivity, and compressive strength decrease. The optimal properties are achieved with 4 wt% Na3PO4·12H2O, resulting in significantly higher compressive strength compared to foamed glass–ceramics prepared from other solid wastes. This study provides valuable guidelines for effectively reusing solid industrial wastes to fabricate foamed glass–ceramics. [ABSTRACT FROM AUTHOR]

To achieve low‐cost clean production in steelmaking plants, a low‐carbon double slag converter steelmaking process (LCDSP) with high dephosphorization efficiency, low lime consumption, and low CO2 emissions is focused on. The average lime consumption in LCDSP has decreased about 25.8%, which can reduce at least about 10.3 million m3 CO2 emissions per converter per year in the current steelmaking plant. The phosphorus enrichment properties of decarbonization slag with different basicities are comprehensively evaluated through LCDSP industrial experiments, mineralogy, and ion–molecule coexistence theory (IMCT). The increase of decarburization slag basicity (DSB) significantly improves the dephosphorization efficiency of molten steel. With increasing the DSB from 2.93 to 3.52, the typical morphology of the P‐rich phase extends from small pieces to long strips and then changes to block shapes with smooth edges. Finally, it forms a massive P‐rich phase with an area of more than 10 000 μm2 with a DSB of 3.80. The phosphorus enrichment properties of decarbonization slag with different DSBs evaluated using multiple perspectives show a consistent change trend. IMCT provides an accurate thermodynamic method for quantitatively predicting the phosphorus enrichment capacity in slag in two stages of LCDSP. [ABSTRACT FROM AUTHOR]

In order to apply and develop fluorine‐free slag in steelmaking, it is of great significance to study the effect of composition for fluorine‐free refining slag on the cleanliness of molten steel which affects its performance directly. The effect of composition of fluorine‐free refining slag with medium and high basicity on the contents of impurity elements for sulfur and oxygen, and characteristics of inclusions in SWRS82B hard wire steel, are investigated systematically. Sulfide capacity of refining slag is estimated based on the Royal Swedish Institute of Technology model. Dissolved oxygen content in molten steel equilibrated by refining slag is calculated based on Factsage software and classical thermodynamics. The calculated results are in good agreement with experimental results. The plasticity of inclusions at high temperature and low temperature is analyzed by phase diagram and Young's modulus calculation. The best cleanliness and inclusions of SWRS82B steel are obtained with slag composition of 53%CaO–19%SiO2–19%Al2O3–7%MgO, which has good melting characteristics. The impurity elements sulfur and oxygen in steel can be controlled for 26 and 19 ppm, respectively, and the average size of inclusions is 2.84 μm. [ABSTRACT FROM AUTHOR]

Iron–manganese solid waste was used to enhance the efficacy of sludge composting, and the humification process and physicochemical properties of the compost were systematically investigated. Iron–manganese slag was added to the composting reactor, the temperature was increased to 69.5°C, and the thermophilic phase was extended to 110 h. Meanwhile, the composting products maintained relatively higher dissolved organic carbon, NH4+-N, protein, and polysaccharide. After composting for 15 days, the humic and fulvic acid ratios in the system with the addition of iron–manganese smelting slag (named as R2) were at least 25% higher than those in the control group, the seed germination index increased to 108%, and the nutrient composition of the composting product reached 8.2%, which was higher than the 6.8% in the raw sludge. Except for arsenic, other heavy metal contents in the R2 system were lower than the Class A limits stipulated by the Chinese Agricultural Sludge Pollutant Control Standard. When iron–manganese slag was added to the sludge piles, microbial metabolism facilitated the release of mineral elements, which enhanced the activities of enzymes such as polyphenol oxidase and alkaline protease, and abundant organic matter was released due to cell lysis and extracellular polymeric substance disruption. Some of the substrates were converted into small-molecule products by microbial actions; meanwhile, precursors such as polysaccharides and proteins were maintained at high levels in the sludge compost, facilitating the formation of humic substances. [ABSTRACT FROM AUTHOR]

This article is a review of literature and patent research on the processing of lead-containing slags and their impact on life. This problem is characteristic of many countries in which industrial metallurgy is directly or indirectly present. The results of the data search allows to systematize the information available today and will undoubtedly be useful for those who deal with the problems of processing lead-containing slags. In addition, data on the influence of lead and lead-containing compounds on human life and its environment are presented. [ABSTRACT FROM AUTHOR]

The study of alkali-activated materials as a replacement for portland cement has been growing in recent years due to the sustainable nature of these materials. Nevertheless, ternary alkali-activated pastes using waste glass as a precursor have been insufficiently studied concerning their rheological, mechanical, and microstructural properties. In addition, there is a lack of research studying alkali-activated mixtures using basic oxygen furnace (BOF) slag and glass waste as precursors. Therefore, this paper aims to study the effect of glass powder (GP) content as a precursor, the effect of the activator ratio in alkali-activated ternary pastes of BOF slag, metakaolin (MK), and GP, and the influence of the Na2SiO3/NaOH ratio on its mixtures. The activator solutions of NaOH and Na2SiO3/NaOH were used in the production of the pastes. The liquid/solid ratio was kept fixed at 0.6 and the molarity of the NaOH solution was fixed at 12 M, seeking to analyze the impact of the Na2SiO3/NaOH ratio, with adopted values of 0.75, 1.5, and 2.5. We also aimed to study the impact of the glass content in the mixture for the values of 10%, 20%, and 25%, replacing the BOF slag. The workability by the minislump test, rheology, compressive strength for 1 and 28 days, and microstructural parameters were analyzed. ANOVA was performed to determine the significance of variables in the workability and compressive strength parameters. Pastes with the highest activator ratio (Na2SiO3/NaOH=2.5) produced better compressive strength (34.74 to 36.11 MPa) and lower minislump spreads (90 to 98 mm) compared with the mixtures with Na2SiO3/NaOH=1.5 and 0.75, besides indicating a denser microstructure, linked to higher production of aluminosilicate gels. Higher GP contents generated pastes with lower mechanical performance (16.7 MPa for Na2SiO3/NaOH=0.75) and microstructural qualities, albeit with better workability (124-mm minislump spread). [ABSTRACT FROM AUTHOR]

Chloride binding capacity is an important factor affecting the durability of concrete, which is directly related with the hydrates of paste. Therefore, this research investigated the chloride binding capacity of calcium silicate hydrates (C-S-H) and Friedel's salt (Fs) to demonstrate the impact of three common mineral admixtures on the binding behavior of pastes. The results show that the binding capacity of pastes can be enhanced when the dosage of fly ash (FA), slag (SL), and silica fume (SF) does not exceed 30%, 45%, and 5%, respectively. The reinforcement effect of SL is the most significant; with 30% dosage, for example, the chloride binding capacity can be increased by 32.0%. Moreover, the single incorporation of FA/SL/SF increases the overall content of C-S-H and decreases the chlorides adsorbed in unit mass C-S-H in general, leading to the result that the binding capacity of paste does not develop positively with the content of C-S-H or Fs. It is thus necessary to take the content and chloride binding performance of phases into consideration when explaining the chloride binding capacity of pastes. Furthermore, Fs fixed chlorides per unit mass paste decline with the increase of FA/SF, while SL dosage has limited impact; further, C-S-H adsorbed chloride per unit mass paste first grows and then reduces for the three series pastes. Moreover, when the NaCl solution concentration is 3.0 mol/L , the chloride content combined by C-S-H is significantly higher than that by Fs in all pastes, with the proportion of the former above 75% in total bound chloride. [ABSTRACT FROM AUTHOR]

The accumulation of municipal solid waste incineration bottom ash (MSWI-BA) not only occupies land, but also leads to severe environmental pollution. In order to improve the utilization of MSWI-BA and reduce carbon emissions, the effect of alkali content on alkali-activated slag (AAS) paste containing 12% MSWI-BA under high-temperature exposure was studied. The alkali contents, i.e., the mass of Na2O in the water glass, were 2%–6% of the total mass of the precursors. The weight loss, thermal shrinkage, and strength of AAS were investigated. The results show that at the same heat treatment temperature, as the alkali content increases, the flexural and compressive strengths of AAS increase and then decrease, reaching the maximum at AAS with 4% alkali content (NS4). As the alkali content increases from 2% to 4%, the higher OH− concentration reduces the Ca dissolution of portlandite in MSWI-BA, resulting in a lower increase in Ca concentration than Si concentration. This leads to a decrease in Ca/Si and an increase in Al/Si of C─ A─ S─ H, which is beneficial for improving the structural stability of C─ S─ H after high temperature. When the alkaline content increases from 4% to 6%, excessive matrix shrinkage leads to an increase in microcracks. It was found that NS4 has the best high-temperature resistance and has good application prospects in engineering. [ABSTRACT FROM AUTHOR]

Calcium pyroniobate (Ca2Nb2O7) as a kind of lead‐free piezoelectric material has been applied for different fields, but the study of isothermal and non‐isothermal growth behaviors of Ca2Nb2O7 in the molten slag is infrequent. In this paper, the in situ thermal analyzer with a single hot thermocouple technique (SHTT) is used to study the growth behaviors of Ca2Nb2O7 in molten slag. In the isothermal temperatures, the Ca2Nb2O7 presents two kinds of growth morphology, including three dimensional (3D) rhombus growth and fibrous one dimensional (1D) growth. The 3D rhombus is grown under the range of 1608 to 1628 K. When the temperature further decreases to 1593 K, the growth behavior of Ca2Nb2O7 becomes fibrous in 1D. Growth velocity affected by the degree of supercooling may account for the phenomenon of two kinds of growth behaviors in different temperatures. In the non‐isothermal growth process, the cooling rate over 10 K min−1 contributes to multiple crystal nucleuses growth of Ca2Nb2O7. The cooling rate below 5 K min−1 leads to single nuclear growth. This paper provides a control guideline for Ca2Nb2O7 growth. [ABSTRACT FROM AUTHOR]