Quantitative phase analysis (QPA) of slags is complex due to the natural richness of phases and variability in sample composition. The number of phases frequently exceeds 10, with certain slag types (EAF, BOF, blends, stainless) having extreme peak overlap, making identification difficult. Another convolution arises from the variable crystallite sizes of phases found in slag, as well as the mixture of crystalline and amorphous components specific to each slag type. Additionally, polymorphs are common because of the complexity of the steelmaking and slag cooling processes, such as the cation-doped calcium aluminum silicate (Ca3Al2O6, C3A, Z = 24) supercell in LMF slag. References for these doped variants may not exist or in many cases are not known in advance, therefore it is incumbent on the analyzer to be aware of such discrepancies and choose the best available reference. All issues can compound to form a highly intricate QPA and have prevented previous methods of QPA from accurately measuring phase components in slag. QPA was performed via the internal standard method using 8 wt% ZnO as the internal standard and JADE Pro's Whole Pattern Fitting analysis. For each phase, five variables (lattice parameters, preferred orientation, scale factor, temperature factor, and crystallite size) must be accounted for during quantitation, with a specific emphasis on not refining crystallite sizes for iron oxides and trace phases as they are inclined to over-broaden and interact with the background to improve the goodness of fit (R/E value). Preliminary investigations show somewhat reliable results with the use of custom file sets created within PDF-4+ specifically targeted toward slag minerals to further regulate and normalize the analysis process. The objective of this research is to provide a standard protocol for collecting data, as well as to update methodologies and databases for QPA, to the slag community for implementation in a conventional laboratory setting. Currently, Whole Pattern Fitting “Modified” Rietveld block refinement coupled with the addition of a ZnO internal standard gives the most accurate QPA results, though further research is needed to improve upon the complex issues found in this study of the QPA of slags.

Weathering of silicate-rich industrial wastes such as slag can reduce emissions from the steelmaking industry. During slag weathering, different minerals spontaneously react with atmospheric CO2 to produce calcite. Here, we evaluate the CO2 uptake during slag weathering using image-based analysis. The analysis was applied to an X-ray computed tomography (XCT) dataset of a slag sample associated with the former Ravenscraig steelworks in Lanarkshire, Scotland. The element distribution of the sample was studied using scanning electron microscopy (SEM), coupled with energy-dispersive spectroscopy (EDS). Two advanced image segmentation methods, namely trainable WEKA segmentation in the Fiji distribution of ImageJ and watershed segmentation in Avizo ® 9.3.0, were used to segment the XCT images into matrix, pore space, calcite, and other precipitates. Both methods yielded similar volume fractions of the segmented classes. However, WEKA segmentation performed better in segmenting smaller pores, while watershed segmentation was superior in overcoming the partial volume effect presented in the XCT data. We estimate that CO2 has been captured in the studied sample with an uptake between 20 and 17 kg CO2/1,000 kg slag for TWS and WS, respectively, through calcite precipitation.

The interaction of NCC-A (no cement content, with tabular corundum) refractory castable with corrosive refining steel slag CaO–Al2O3–SiO2–MgO–(FeO, MnO) was studied with static crucible corrosion tests. The corrosion process was evaluated using chemical and phase analyses, and the macro- and microstructures on the corrosion boundary of slag–refractory materials were investigated. We describe the corrosion progress and explain the NCC-A corrosion mechanism by oxide metallurgical slags. The alumina refractory material surface was wetted with molten oxide slag (contact angle θ1390°C from 10° to 20°). The slag penetrated through dissolution of the matrix (fine alumina cement), and the Ca–Si–Al slag, enriched with alumina, attacked the corundum grog. Marked changes in the chemical composition of the slag had an impact on the primary crystallization temperature. As the concentration of Al–O complexes increased in the slag, the binding parameters in Si–O complexes changed and complex tetrahedral units (Al–O–Si) and (Al–O–Mg) were created. Analyses of the corrosion interface grog show that calcium ions diffuse through structural defects in the corundum but Mg2+ diffusion was not observed. A sharp interface is observed between the slag and the corroded corundum layer. Differences in the chemical composition of the slag in the corrosion zone affected the convention stream, and formed the concave corrosion profile of the crucible.

Meroe is one of Africa's most famous archaeological sites, renowned not least for its evidence of ironworking. Yet, the extensive slagheaps that characterise the site have received little archaeological attention. To illuminate the chronology and distribution of these remains, this article combines extant excavation data with the results of recent site-wide surface and geoprospection survey, and ongoing slagheap excavation and radiocarbon dating. The slagheaps date predominantly to either the Early (Napatan) or Late (late/post-Meroitic) periods, with little evidence for activity between c. 300 BC and AD 300—precisely when Meroe was the capital of the Kingdom of Kush—indicating significant reorganisation of the city's industrial base at this time.

The S. Domingos abandoned mine is a major source of pollutant-metals contamination. Slags from the 19th-20th century contain the most hazardous material. However, the release of pollutant metals depends on the metal-retention capability of weathering products. This work shows that Zn is not effectively retained by these weathering products while As and Pb are partially stored in sulphates. Copper, on the other hand, has a different behaviour and is the most leachable of the elements studied.

Cementitious matrices are being assessed for immobilization of radioactive wastes. This paper discusses some mineralogical aspects of cement chemistry and the uses of siliceous minerals as selective sorbants to enhance immobilization potential.

Studies of sorption and leaching of caesium from pulverized fuel ash (PFA), blast furnace slag, tobermorite, xonotlite, and clinoptilolite are reported. The role of incorporation of these additives in cement and the effect on the nature of the composite matrix on caesium behaviour has been investigated. Specific mechanisms of the interaction of additives with highly alkaline cement environment are described. While slags, PFA, and clinoptilolite undergo reaction at different rates, tobermorite and xonotlite appear to be stable in cement.

Slag dumps occur at several historical smelting sites in north Queensland, Australia. The microcrystalline slags contain primary slag phases, relict flux, ore and furnace materials and secondary weathering related minerals. Common primary slag phases are glass, Zn-rich fayalite (± Zn-rich kirschsteinite) and Zn-rich hedenbergite. Other minor minerals include wollastonite, Zn-rich melilite, Zn-rich iscorite (Fe7SiO10), magnetite as well as a number of sulphides (pyrrhotite, galena, bornite, sphalerite, wurtzite), metallic phases (Ag, Cu, Pb, Sb), alloys (Cu3Sn), and unknown metal compounds. The slag materials contain wt.% concentrations of Zn and elevated levels of Ag, As, Cd, Cu, Ni, Pb, Sb and W. Glass, hedenbergite and fayalite/kirschsteinite are the main repositories of Zn, whereas much of the Cu and Pb is hosted by glass, sulphides, Cu3Sn alloys, metallic Cu and Pb, and unknown CuSb, AsSnPb and FeAsCu compounds. The slags are undergoing contemporaneous reaction with air and rainwater. The weathering results in the release of metals and metalloids from primary slag phases, particularly from glass, and the partial immobilization of these metals in secondary soluble and insoluble minerals in the slag heaps. Zinc exhibits pronounced chemical mobility and reports together with elevated Ca and sulphate into surface seepages (up to 10.2 mg l−1 Zn at pH 6.97). The slag dumps represent long-term sources of metal pollutants, particularly of Zn, to local ground and surface waters.

The reactivity of primary Pb metallurgical slags in high-molecular-weight (HMW) organic solutions has been studied in order to determine the processes of release and attenuation of metal and metalloid contaminants (Pb, Zn, Cu, As) in 'soil-like' environments. Slag was submitted to a 112-day batch leaching experiment in Suwannee River fulvic acid solution and peat water (∼50 mg DOC l–1). The leaching was coupled with investigation of the secondary phases (SEM/EDS, Raman microspectrometry) and thermodynamic speciation-solubility modelling using MINTEQA2. Metals and As are released in large amounts during the early stage of the experiment, followed by a decrease in the concentrations in the leachate as a result of adsorption on secondary (hydrous) ferric oxides (HFO/FO), predicted by MINTEQA2 calculations and confirmed on the leached slag surface by SEM and Raman spectrometry. Compared to other contaminants, Zn exhibits more pronounced mobility and is adsorbed on HFO/FO only at pH >7. Such a scavenging process may be predominant during the long-term interaction of slag with an HMW organic solution of real soil. As a result, the soil cover and subsequent re-vegetation of slag dumps may be considered as a possible scenario for slag management.

Slags sourced from a derelict zinc–lead–copper–silver–tungsten mine were examined for their bulk elemental composition and mineralogy. pH, oxidation–reduction potential, and the leachability of selected elements (sulphur, calcium, iron, copper, zinc, and lead) were assessed during a 130-day deionised water extraction conducted under oxic conditions. Slags were rich in silicon, iron, copper, zinc, and lead, hosted within minerals including quartz (SiO2), goethite [FeO(OH)], augite [Ca(Mg,AI,Fe)Si2O6], and lead (Pb0). Leachates from the slags increased in analyte concentration throughout the 130-day experiment, with iron, copper, zinc, and lead attaining >5 mg l−1 in some samples. These findings indicate that this pyrometallurgical waste should not be considered environmentally inert, as leachates emanating from them in the field might pose a significant risk to the environment.

Phases present in slags from Araxá (Brazil), Oka (Quebec) and Fen (Norway) resulting from the production of ferroniobium by the aluminothermic reduction of pyrochlore-group minerals are a function of composition of the pyrochlore feed and the diverse fluxes (CaO, CaF2) added to the alumina and iron oxide used in the reduction process. Absent from all slags investigated are Fe-bearing compounds. All of the slags are modally-dominated by prismatic crystals of β-alumina or hibonite, with a wide variety of Th-Ba-Ti-Nb-Al-oxide compounds and silico-aluminate glasses occurring in the interstices between these crystals. Slag from Fen consists of a framework of β-alumina (Ba and/or CaTi varieties) with a barian titanian niobate, considered to be an highly reduced Nb3+- and Ti3+-bearing anion deficient perovskite, as the first oxide phase to crystallize. This was followed by a Zr-Ti-Th-niobate (21.7–24.1 wt.% ThO2), a Nb-rich, Thbearing zirconolite-like phase (17.7–21.2 wt.%; Nb2O5; 6.8–9.5 wt.% ThO2) and diverse Th-Nb-rich, Alpoor (< 1 wt.% Al2O3) perovskites (29.4–40.5 wt.% Nb2O5; 3.3–11.4 wt.% ThO2). The latter represents a NaNbO3–CaTiO3–Na2/3Th1/3TiO3–ThTi2O6 solid solution. Late Na-rich silicate glass contains celsian. Slag from Araxá also consists of a framework of β-alumina (Ti-poor). Interstitial compounds differ from Fen in being predominantly rare-earth element (REE)-Nb-Al-Th-perovskites belonging to a REEAlO3–Ca2AlNbO6–CaTiO3–ThTi2O6 solid solution with minor NaNbO3 and CaZrO3, and compositionally diverse barium calcium aluminates [(Ba, Ca)Al2O4] set in a F-bearing (6–7 wt.%) Na-Ba-Si-aluminate glass with minor Ba4Nb2O9, CaF2, BaF2 and NaF. Slag from Oka consists of a framework of hibonite [(Ca, REE) (Al, Ti, Mg)12O19] zoned with respect to the REE content. Interstitial compounds are CaZr4O9, Nb-Th-poor perovskites belonging to the REEAlO3–CaTiO3 series with minor CaZrO3 set in a F-bearing (5–6 wt.%) calcium aluminate glass. These data demonstrate that during ferroniobium production REE, Zr, Th, U and significant amounts of Nb are sequestered in the oxide phases in accord with their lithophile geochemical character. None of these elements are present as compounds in the siderophillic ferroniobium alloys. These data demonstrate that the aluminothermic reduction process results in the loss of significant amounts of Nb to the slag. Perovskite-group compounds are present in all of the slags but differ widely in their composition as a result of compositional differences in the feed pyrochlores and fluxes added to the smelting process. Slags originating from ferroniobium production are enriched in Th and U and could be considered as an environmental hazard if these elements are mobilized during chemical weathering of slag.

Irradiation is one of the characteristic conditions that nuclear wasteforms must withstand to assure integrity during their service life. This study investigates gamma irradiation resistance of an early age slag cement-based grout, which is of interest for the nuclear industry as it is internationally used for encapsulation of low and intermediate level radioactive wastes. The slag cement-based grout withstands a gamma irradiation dose of 4.77 MGy over 256 h without reduction in its compressive strength; however, some cracking of irradiated samples was identified. The high strength retention is associated with the fact that the main hydration product forming in this binder, a calcium aluminum silicate hydrate (C–A–S–H) type gel, remains unmodified upon irradiation. Comparison with a heat-treated sample was carried out to identify potential effects of the temperature rise during irradiation exposure. The results suggested that formation of cracks is a combined effect of radiolysis and heating upon irradiation exposure.

The goal of zero-waste is one of the main challenges of modern steel industry, which over the past 20 years has been committed to increase the recovery and the use of by-products generated during the ironmaking and steelmaking processes. Among the main by-products generated during iron and steel production, such as slags, dusts and sludges, slags constitute about 90% of the total. Slags are currently used in various fields (such as cement production, road construction, environmental recovery in landfill covers, as fertilizer and soil conditioner, etc.) according to their chemical features, which depend on production process origin. In Italy, in particular for example, BF (Blast Furnace) slag is used for cement production while BOF (Basic Oxygen Furnace) slag without iron (inert slag) is used as landfill cover, in compliance with Italian legislation. In Germany, BF and BOF slag use as fertlisers and liming materials has a long tradition. Although in recent years slag use has increased, the application for agriculture purposes needs to be further investigated. Slag can be used as a soil conditioner (high content of Ca and Mg), Si supply (improves the crops resistance to pests and diseases), P fertilizer production and micro-nutrients supply. Use of slags can affect human health and environment, because of heavy metal content, which can leache to groundwater or be transferred to surface water. The assessment of risk to the environment based on slag application requires further investigation. This represents an opportunity for both the steel and fertilizer industries to promote natural resources savings, CO2 emission reductions, landfill waste prevention as well as social awareness of sustainability of some industrial activities. The BOF slag has been shown to be useful as liming material for acidic soil amendment and it can replace commercial fertilizers. Different effects on crop yields and on soil parameters can be found, depending on soil characteristics and climate conditions. In Middle Europe, with humid climate, lime losses through leaching of up to 0.5 t CaO/ha have to be replaced with liming material to prevent acidification. Evaluation of long-term field trials with slag liming materials can give information about the impact of slag applications on crop management and the environment. In Mediterranean regions, such as in Italy, arable soils rarely show acidic characteristics. Alkaline soils from coastal areas are often rich in sodium content, due to seawater intrusion and irrigation with saline water. The aim of this research is also to investigate the application of BOF slag to these soils, in order to assess the effect of Ca contained in slag in balancing negative Na effects. This paper is based on the preliminary study and experiments carried out within an ongoing RFCS (Research Fund for Coal and Steel) project.

The influence of LF refining slag composition on desulfurization and inclusionmodification was investigated through industrial experiments and thermodynamic analysis.The results show that the sulfide capacity decreases with the decrease in(%CaO)/(%SiO2)and (%CaO)/(%Al2O3) of the slag. The theoretical sulfur distributions agreewell with the analysis results when the sulfide capacity is calculated by Zhang’s model,but the theoretical sulfur distributions are higher than the analysis results when thesulfide capacity is calculated by the KTH model. During the LF refining process,inclusions are transformed from Al2O3 inclusions into CaO-MgO-Al2O3 system inclusions. Higher slagbasicity results in higher CaO and MgO and lower Al2O3 content inclusions in moltensteel at the end of the LF process.

Melting of Direct Reduced Iron (DRI) pellets in Electric Arc Furnaces (EAF) in steelmaking production is a common practice worldwide. Mathematical models are proper tools to study the phenomena involved in melting DRI. In this work we develop a mathematical model to predict melting kinetics of DRI in a liquid slag bath. The model is successfully validated against experimental results and it is used to develop a process analysis to estimate the effects of DRI size, stirring conditions, and temperatures of the bath and pellet on the melting kinetics of DRI.