Electric Arc Furnace Steel Slag Research Articles

Effect of electric arc furnace slag on growth and physiology of maize (Zea maysL.)

Basic slag, used in this study as a potential source of certain nutrients, is a byproduct of the production of steel in electric arc furnace (EAF). A pot experiment with two nutrient-poor substrates was conducted to investigate to compare the effect of EAF steel slag and fertilizers NPK + F e on growth and availability of specific nutrients to maize. Mineral content of both substrate and plant leaves, growth, chlorophyll fluorescence and photosynthetic pigments were measured following six weeks of cultivation. As steel slag also contains trace amounts of heavy metals, certain oxidative parameters (antioxidative enzyme activities and lipid peroxidation) were evaluated as well. The steel slag improved soil mineral composition, increased above ground maize biomass by providing Fe, Mn, Mg, K and partly P and improved photosynthetic parameters. The potential phytotoxicity of EAF slag containing substrates was not determined as evaluated by MDA (malondialdehyde), GR (glutathione reductase) and APX (ascorbate peroxidase) levels. The obtained results show that EAF steel slag is comparable to NPK + F e in supplying nutrients for maize growth, indicating the potential of EAF steel slag as an inexpensive and non-phytotoxic nutrient supplier especially in poor soils.

Assessment of EAF Steel Slag Solubility by Statistical Design

Electric arc furnace (EAF) steel slag solubility was studied using experimental design and statistical analysis. The solutions between pH 4 and 10, were mixed with the EAF steel slag for 0.5 hours at 350 rpm. The effects of the operating parameters, individually and their interaction, on the dissolution of slag elements were assess using full factorial design in the statistical design of experiment. The various parameters studied were pH (4-10), size (+0.2-1.2 mm), speed (0-700 rpm) and temperature (26-50°C). The results of the experimental design indicated that the main significant parameter within the ranges studied for Cr (VI) dissolution in solution was higher speed, lower size for Ca dissolution while for Si, was the positive interaction of speed and size. Maximum Cr (VI) of 0.0104 mg/L was obtained in solution at pH 10, slag size of 0.2 mm, temperature of 50°C and rotational speed of 700 rpm. Also, complimenting the solubility studies was slag characterization using XRF, XRD and SEM/EDX analysis. From these results, it can be concluded that the operating parameters considered individually and their interaction have effect on the solubility of EAF steel slag.

Laboratory evaluation of warm mix asphalt mixtures containing electric arc furnace (EAF) steel slag

This paper presents the results of a laboratory study which was aimed to verify possibility of using electric arc furnace (EAF) steel slag (SS) in substitution of natural limestone (LS) aggregates in warm mix asphalt (WMA) mixture. The SS was used as fine and coarse portion of aggregate gradation in HMA mixtures, and as coarse portion of aggregate gradation in WMA mixture. The surface texture of both LS and SS aggregates was observed through scanning electron microscope (SEM). The results illustrated that the porosity and the roughness of the SS aggregate are higher than that of the LS aggregate. Moreover, laboratory tests results indicated that use of coarse SS aggregate in WMA mixture enhances Marshall stability, resilient modulus, tensile strength, resistance to moisture damage and resistance to permanent deformation of the mixture. Hence use of coarse electric arc furnace steel slag aggregate in production of WMA mixture is recommended.

Synthesis, characterization and properties of calcium ferroaluminate belite cements produced with electric arc furnace steel slag as raw material

This study investigated the use of 10 (M1), 17 (M2) and 27wt.% (M3) electric arc furnace steel slag (EAFS) as a raw material in the production of calcium ferroaluminate belite cement clinker, after firing at 1320°C. The thermal behavior of the raw meals was studied by TG/DSC and XRD whereas for the analysis of the clinkers, XRD/QXRD, SEM/EDS and EPMA were employed. The resulting clinker was co-grinded with 5 and 20wt.% Flue Gas Desulfurization (FGD) gypsum and the properties were determined by a series of tests in accordance to EN standards. The evolution of hydration was investigated by SEM and the development of compressive strength. The results revealed that the formed phases in the clinkers were C2S, C4AF and C4A3Ŝ. The main hydration products were ettringite, AFm and hydrogarnet. The leached CrVI was below 1ppm in M3. Compressive strength in cements with 5wt.% FGD gypsum was (in MPa): 18.3 for M1, 14.3 for M2 and 7.8 for M3 at 28days, whereas for 20wt.% FGD gypsum, the values were almost doubled.

Cementitious property modification of basic oxygen furnace steel slag

In this paper, we propose a new method for modifying the chemical and mineralogical compositions of steel slag by adding industrial wastes to molten basic oxygen furnace steel slag (BOFS). The effects of the composition of the modifying component and the modification parameters on the structure and the cementitious properties of modified steel slag (MSS) are investigated in a laboratory, and a pilot-scale modification research is conducted. Results indicate that the appropriate ratio of BOFS, electric arc furnace steel slag (EAFS) and coal bottom ash in MSS is 85:12.75:2.25. The modification can reduce the free-CaO content of pilot-scale MSS and remarkably improve its cementitious property. The mineralogical composition and the structure of BOFS can be modified by reacting it with EAFS and coal bottom ash at a high temperature generated by the waste heat of the molten steel slag.

Fatigue Performance of Asphalt Concretes Made with Steel Slags and Modified Bituminous Binders

This paper describes the results of a research aimed at investigating the fatigue resistance performances, determined by means of the four-point bending test (4PBT), of bituminous mixtures (SMA and traditional ones) for base courses and wearing courses, made with Electric Arc Furnace (EAF) steel slag and bitumen modified with crumb rubber or SBS polymers. The fatigue behaviour was also studied after long-term ageing, in order to check the effectiveness of the crumb rubber modification (by wet process) in reducing the fatigue damage in heavily oxidized mixtures. For both unaged and aged conditions, the asphalt rubber mixes presented better fatigue behaviour than the reference mixtures made with polymer modified bitumen.

Evaluation of the Leaching Behavior of Hexavalent Chromium from Malaysian Electric Arc Furnace Steel Slag

This study investigates the leaching behavior of hexavalent chromium (Cr (VI)) from both industrial electric arc furnace steel slag and steel slag modified with up to 2% wt Cr2O3. The study was performed with European standard batch leaching test for 15 days and the lixiviant used were alkaline, de-ionized and rain water. The experimental work was also complimented with slag characterization using XRF, XRD and SEM/EDX analysis. After 15 days, Cr (VI) was found to be highest in rain water (0.016 mg/L) and lowest in de-ionized water (0.002 mg/L). With more Cr2O3 in EAF slag, more Cr will leach out based on the 2% wt Cr2O3 addition. Besides the lixiviant used, slag stirring speed and liquid to solid ratio also affect the dissolution of Cr (VI). With up to 2 wt % Cr2O3 in EAF slag, Cr (VI) dissolution was still lower than the threshold of 0.1 mg/L set by USEPA for public water systems. The analysis also indicated that the relative amounts of soluble basic and acidic oxides in the slag will affect the dissolution of Cr (VI).

Improvement of Post-fire Properties of Concrete with Steel Slag Aggregate

In this paper electric arc furnace (EAF) steel slag as by-products from the steel production industry is considered as an aggregate which could improve post-fire properties of concrete due to the fact that it is the material that is made at the temperatures of up to 1650°C. For this purpose five high-strength concrete (HSC) mixtures were prepared: reference mixture with dolomite aggregate and four concrete mixtures with two types of steel slags available from Croatian steel plants as a coarse aggregate. Two slag based concrete mixtures were prepared with the slags that were previously thermally treated. At the age of 56 days concrete specimens have been exposed to high temperatures up to 800°C. Upon cooling of the specimens their residual properties (compressive strength, modulus of elasticity, weight loss and ultrasonic pulse velocity) were tested and compared with the same properties of the reference concrete. Microstructural analysis based on SEM observations was also done. To clarify the impact of each individual component of concrete mixtures on the behaviour of concrete under high temperatures the dilatometer analysis of cement paste and all aggregate types used in studied mixtures was conducted. The obtained results showed that slag could improve fire performance of concrete in the temperature range up to 400°C. This improvement is especially observable in the case of concrete made with the previously thermally treated slag.

Steel Slag Filters to Upgrade Phosphorus Removal in Constructed Wetlands: Two Years of Field Experiments

Electric arc furnace steel slag (EAF-slag) and basic oxygen furnace steel slag (BOF-slag) were used as filter substrates in two horizontal subsurface flow filters (6 m(3) each) designed to remove phosphorus (P) from the effluent of a constructed wetland. The influences of slag composition, void hydraulic retention time (HRTv), temperature, and wastewater quality on treatment performances were studied. Over a period of almost two years of operation, the filter filled with EAF-slag removed 37% of the inlet total P, whereas the filter filled with BOF-slag removed 62% of the inlet total P. P removal occurred predominantly via CaO-slag dissolution followed by Ca phosphate precipitation. P removal efficiencies improved with increasing temperature and HRTv, most probably because this affected the rates of CaO-slag dissolution and Ca phosphate precipitation. It was observed that long HRTv (>3 days) can cause high pH in the effluents (>9) as a result of excessive CaO-slag dissolution. However, at shorter HRTv (1-2 days), pH values were elevated only during the first five weeks and then stabilized below a pH of 9. The kinetics of P removal were investigated employing a first-order equation, and a model for filter design was proposed.

Fatigue Behavior Characterization of Bituminous Mixtures Made with Reclaimed Asphalt Pavement and Steel Slag

The paper discusses the results of a laboratory evaluation and a theoretical study on the fatigue behaviour of bituminous mixtures with Reclaimed Asphalt Pavement aggregate and electric arc furnace steel slag, used in different proportion.The experimental investigation was performed with the four-point bending test. The fatigue life has been evaluated by three different approaches, based on the 50% reduction of the initial stiffness modulus, the dissipated energy and the damage accumulation.With respect to the reference mixture, composed by a natural aggregate skeleton, the bituminous mixtures with RAP aggregate and steel slag have presented improved fatigue properties and performance.

Heavy metal adsorption changes of EAF steel slag after phosphorus adsorption

A kind of electric arc furnace (EAF) steel slag was phosphated, and its isothermal and dynamic adsorptions of copper, cadmium, and lead ions were measured to determine if heavy metal adsorption changes after phosphorus adsorption. The surface area increased greatly after the slag was phosphated. Isothermal adsorption experiments showed that the theoretical Q(max) of the EAF steel slag on Cu(2+), Cd(2+), and Pb(2+) improved 59, 50, and 89% respectively after it was phosphated. Dynamic adsorption results showed that the greatest adsorption capacities of unit volume of Cu(2+), Cd(2+), and Pb(2+) were 2.2, 1.8, and 1.8 times that of the column packed with original EAF steel slag when the column was packed with phosphate EAF steel slag at the same heavy metal ion concentration. The breakthrough time, the exhaustion time and elution efficiency of the column also increased when the column was packed with phosphated EAF steel slag compared with that packed with original EAF steel slag. Phosphorus adsorption could further improve the heavy metal ion adsorption of the EAF steel slag.

Performance of concrete mixtures made with electric arc furnace (EAF) steel slag aggregate produced in the Arabian Gulf region

This research aims to investigate the effect of using electric arc furnace (EAF) steel slag as coarse aggregate in concrete. Properties of fresh and hardened concrete were evaluated for five concrete mixtures with different grades (30, 50 and 70MPa), and the inclusion of supplementary cementing materials (SCM) such as fly ash class F (FA) and silica fume (SF). EAF steel slag beneficially affected the engineering properties (i.e. physical, mechanical and durability) of the produced concrete. Also, it would be more beneficial if the grading of the produced EAF steel slag is controlled and adjusted to better improve the quality of the produced concrete.

A Laboratory Study of the Treatability of Synthetic Stormwater Under Varying Conditions Using Electric Arc Furnace Steel Slag

The investigation of electric arc furnace (EAF) steel slag as a viable add-on technology to existing stormwater systems for the removal of dissolved phosphorus (P) was extended to explore the effects of varying environmental and treatment system conditions. Parameters such as stormwater composition, P concentration, metal concentration, pH, temperature, slag mass and slag particle size were varied. Observations relating to the method of P removal via EAF slag were also carefully considered to explain removal mechanisms involved. Results demonstrated that, although physisorption contributed to P reduction, it was not the key P removal mechanism. Instead, precipitation was observed to be a key removal pathway as evidenced by the correlation between the loss of iron (Fe) from slag and the amount of P removed from solution. The reduced removal of P by slag in a copper-dominant stormwater solution was attributed to the formation of a stable complex formed by the interaction of copper with the slag via the ion-exchange surface model. The stability of this complex inhibits the loss of Fe from the EAF slag and, consequently, P removal by means of precipitation. In terms of the effect of changing environmental and treatment system conditions on the P removal process, stormwater composition, P concentration, metal concentration, pH, temperature, slag mass and slag particle size were found to significantly influence the effectiveness of EAF slag in removing P from a given stormwater system. It was also established that a number of combinations of these factors influence P uptake differently.

Phosphate removal from synthetic and real wastewater using steel slags produced in Europe

Electric arc furnace steel slags (EAF-slags) and basic oxygen furnace steel slags (BOF-slags) were used to remove phosphate from synthetic solutions and real wastewater. The main objective of this study was to establish an overview of the phosphate removal capacities of steel slags produced in Europe. The influences of parameters, including pH, and initial phosphate and calcium concentrations, on phosphate removal were studied in a series of batch experiments. Phosphate removal mechanisms were also investigated via an in-depth study. The maximum capacities of phosphate removal from synthetic solutions ranged from 0.13 to 0.28 mg P/g using EAF-slags and from 1.14 to 2.49 mg P/g using BOF-slags. Phosphate removal occurred predominantly via the precipitation of Ca-phosphate complexes (most probably hydroxyapatite) according to two consecutive reactive phases: first, dissolution of CaO-slag produced an increase in Ca2+ and OH− ion concentrations; then the Ca2+ and OH− ions reacted with the phosphates to form hydroxyapatite. It was found that the release of Ca2+ from slag was not always enough to enable hydroxyapatite precipitation. However, our results indicated that the Ca2+ content of wastewater represented a further source of Ca2+ ions that were available for hydroxyapatite precipitation, thus leading to an increase in phosphate removal efficiencies.

Model of Phosphorus Precipitation and Crystal Formation in Electric Arc Furnace Steel Slag Filters

The objective of this study was to develop a phosphorus retention mechanisms model based on precipitation and crystallization in electric arc furnace slag filters. Three slag columns were fed during 30 to 630 days with a reconstituted mining effluent at different void hydraulic retention times. Precipitates formed in columns were characterized by X-ray diffraction and transmission electronic microscopy. The proposed model is expressed in the following steps: (1) the rate limiting dissolution of slag is represented by the dissolution of CaO, (2) a high pH in the slag filter results in phosphorus precipitation and crystal growth, (3) crystal retention takes place by filtration, settling and growth densification, (4) the decrease in available reaction volume is caused by crystal and other particulate matter accumulation (and decrease in available reaction time), and (5) the pH decreases in the filter over time if the reaction time is too low (which results in a reduced removal efficiency). Crystal organization in a slag filter determines its phosphorus retention capacity. Supersaturation and water velocity affect crystal organization. A compact crystal organization enhances the phosphorus retention capacity of the filter. A new approach to define filter performance is proposed: saturation retention capacity is expressed in units of mg P/mL voids.

Reuse of steel slag in bituminous paving mixtures

This paper presents a comprehensive study to evaluate the mechanical properties and environmental suitability of electric arc furnace (EAF) steel slag in bituminous paving mixtures. A variety of tests were executed on samples of EAF slag to characterize the physical, geometrical, mechanical and chemical properties as required by UNI EN specifications, focusing additionally on the volumetric expansion associated with hydration of free CaO and MgO. Five bituminous mixtures of aggregates for flexible road pavement were designed containing up to 40% of EAF slag and were tested to determine Marshall stability and indirect tensile strength. The leaching behaviour of slag samples and bituminous mixtures was evaluated according to the UNI EN leaching test. The tested slag showed satisfactory physical and mechanical properties and a release of pollutants generally below the limits set by the Italian code. Tests on volume stability of fresh materials confirmed that a period of 2–3 months is necessary to reduce effects of oxides hydration. The results of tests performed on bituminous mixtures with EAF slag were comparable with the performance of mixtures containing natural aggregates and the leaching tests provided satisfactory results.

Performance comparative analysis of stone mastic asphalts with electric arc furnace steel slag: a laboratory evaluation

The paper presents the results of a laboratory study, aimed at verifying the possibility to use two particular typologies of electric arc furnace (EAF) steel slags, in substitution of the natural aggregates, in the composition of stone mastic asphalt (SMA) for flexible pavements. The research has been articulated in a preliminary study of the chemical, leaching, physical, and mechanical properties of the EAF steel slag, and in the following mix design and performance characterization of the bituminous concretes, through gyratory compaction tests, permanent deformations tests, stiffness modulus tests at various temperatures, fatigue tests and indirect tensile strength tests. All the mixtures with EAF slag have satisfied the requisites for acceptance in the road sector technical standards, thus resulting as suitable for use in the construction of road infrastructures, moreover presenting higher mechanical characteristics than those of the corresponding asphalts with full natural aggregate.

Valorisation of electric arc furnace steel slag as raw material for low energy belite cements

In this paper, the valorisation of electric arc furnace steel slag (EAFS) in the production of low energy belite cements is studied. Three types of clinkers were prepared with 0 wt.% (BC), 5 wt.% (BC5) and 10 wt.% (BC10) EAFS, respectively. The design of the raw mixes was based on the compositional indices lime saturation factor (LSF), alumina ratio (AR) and silica ratio (SR). The clinkering temperature was studied for the range 1280–1400 °C; firing was performed at 1380 °C based on the results regarding free lime and the evolution of microstructure. In order to activate the belite, clinkers were cooled fast by blown air and concurrent crushing. The results demonstrate that the microstructure of the produced clinkers is dominated by belite and alite crystals, with tricalcium aluminate and tetracalcium-alumino-ferrite present as micro-crystalline interstitial phases. The prepared cements presented low early strength development as expected for belite-rich compositions; however the 28-day results were 47.5 MPa, 46.6 MPa and 42.8 MPa for BC, BC5 and BC10, respectively. These values are comparable with OPC CEMI 32.5 N (32.5–52.5 MPa) according to EN 197-1. A fast setting behaviour was also observed, particularly in the case of BC10, whereas soundness did not exceed 1 mm.

Environmental Impacts of Asphalt Mixes with Electric Arc Furnace Steel Slag

Electric arc furnace (EAF) steel slag can be used as an alternative high-quality material in road construction. Although asphalts with slag aggregates have been recognized as environmentally acceptable, there is a lack of data concerning the potential leaching of toxic Cr(VI) due to the highly alkaline media of EAF slag. Leaching of selected water extractable metals from slag indicated elevated concentrations of total chromium and Cr(VI). To estimate the environmental impacts of asphalt mixes with slag, leachability tests based on diffusion were performed using pure water and salt water as leaching agents. Compact and ground asphalt composites with natural aggregates, and asphalt composites in which the natural aggregates were completely replaced by slag were prepared. The concentrations of total chromium and Cr(VI) were determined in leachates over a time period of 6 mo. After 1 and 6 mo, the concentrations of some other metals were also determined in the leachates. The results indicated that chromium in leachates from asphalt composites with the addition of slag was present almost solely in its hexavalent form. However, the concentrations were very low (below 25 μg L) and did not represent an environmental burden. The leaching of other metals from asphalt composites with the addition of slag was negligible. Therefore, the investigated EAF slag can be considered as environmentally safe substitute for natural aggregates in asphalt mixes.

DEFINING OF EAF STEEL SLAG APPLICATION POSSIBILITIES IN ASPHALT MIXTURE PRODUCTION / ELK PLIENO ŠLAKO PANAUDOJIMO GAMINANT ASFALTO MIŠINĮ GALIMYBĖS / ВОЗМОЖНОСТИ ПРИМЕНЕНИЯ СТАЛЬНОГО ШЛАКА ИЗ ДУГОВОЙ СТАЛЕПЛАВИЛЬНОЙ ПЕЧИ ДЛЯ ПРОИЗВОДСТВА АСФАЛЬТОВОЙ СМЕСИ

Electric arc furnace (EAF) steel slag, generated from carbon steel production process, is the most interesting from the asphalt technology point of view. This paper aims to explore the feasibility of utilizing steel slag as aggregates in asphalt mixtures. Characterization of EAF slag was carried out through examination of its physical and chemical properties with special emphasis on chemical and structural characteristics. Optical Microscopy (OM), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectrometry (EDS) and γ-spectrometric analysis were employed to study the texture, morphology and composition of steel slag. Volume properties of steel slag were also evaluated as compared to those of natural aggregates. For this purpose the specimens of EAF slag were taken from the regular production processes in CMC Sisak, Croatia, Steel mill. The results which were obtained by testing geometric, physicalmechanic properties, as well as the properties of duration on the specimen of electric furnace steel slag of CMC Sisak, when compared to steel slag properties of other steel producers (Acroni, Jesenice, Slovenia and Štore Steel, Štore, Slovenia) and with properties of natural aggregates, have satisfied the conditions for manufacturing mixtures of the tested steel slag and natural stone, which can be used in asphalt production. In comparison to the natural aggregates, which are used in asphalt mixtures on highways and roads with heavy traffic, the examined steel slag has equally good physical and mechanical properties, while it is significantly better when it comes to resistance to polishing. Special attention has been given to the free CaO and free MgO, which can cause volume instability, thus limiting the use of steel slag in road construction. Santrauka Nagrinėjamos plieno šlako panaudojimo asfalto mišiniui gaminti galimybės. Šis šlakas susidaro elektros lanko krosnyje (ELK) anglies plieno gamybos procese. Nagrinėjamos fizikinės bei cheminės šlako savybės, pateikiamos cheminės ir struktūrines charakteristikos. Plieno šlako tekstūra, morfologija ir sudėtis nustatyta taikant optinę mikroskopiją (OM), rentgeno spindulių difrakciją (RSD), skenuojančiąją elektroninę mikroskopiją (SEM), energijos dispersinę spektrometriją (EDS) bei spektrometrinę analizę. ELK šlako mėginiai buvo paimti iš plieno gamyklos CMC Sisak, Kroatijoje. Šių mėginių geometrinės, fizikinės ir mechaninės bei patvarumo savybės buvo lyginamos su kitų šlakų (Acroni, Jesenice, Slovenija ir Store steel, Štore, Slovėnija) ir natūralių agregatų savybėmis. Gauti rezultatai patvirtino tirto plieno šlako bei natūralaus akmens panaudojimo gaminant asfaltą galimybes. Natūralūs agregatai, naudojami asfalto mišiniuose tiesiant greitkelius ir intensyvaus eismo kelius, bei tiriamas plieno šlakas turi panašių gerų fizikinių bei mechaninių savybių, tačiau ELK šlakas yra atsparesnis gludinimui. Daug dėmesio buvo skirta laisviesiems CaO ir MgO, lemiantiems medžiagos nepatvarumą. Šie oksidai yra pagrindinis veiksnys, ribojantis plieno šlako naudojimą asfaltui gaminti. Резюме В статье ставилась цель исследовать возможности применения стальных шлаков, образующихся в процессе производства стали в дуговой сталеплавильной печи (ДСП), для производства асфальтовой смеси. Исследовались физические и химические свойства шлака из ДСП. Текстура, морфология и состав стального шлака определялись с использованием оптической микроскопии, дифракции рентгеновских лучей, электронной микроскопии, энергодисперсной спектрометрии и γ-спектрометрического анализа. Образцы шлака из ДСП были взяты на заводе по производству стали в Хорватии. Геометрические, физико-механические и прочностные свойства образцов сравнивались со свойствами других шлаков (из Словении) и с натуральными материалами. Полученные результаты подтвердили возможность применения шлака исследованной стали и натурального камня для производства асфальтовой смеси. Натуральные материалы, применяемые в асфальтовых смесях при строительстве магистралей и дорог с интенсивным движением, и исследованный стальной шлак обладают приблизительно одинаковыми хорошими физико-механическими свойствами, однако шлак из ДСП более устойчив при шлифовании. При анализе большое внимание также уделялось свободным CaO и MgO, вызывающим нестабильность материала. Эти оксиды являются основным фактором, лимитирующим применение стального шлака при производстве асфальта.