Types Of Steel Slag Research Articles

Effect of activator type and Pozzocrete waste on the mechanical and microstructural properties of eco-friendly geopolymer incorporating electric arc furnace slag

ABSTRACT The precursor type and activator are two primary factors that significantly affect the properties of geopolymers. Most of the previous studies used byproduct materials such as fly ash (FA) and slag as geopolymer precursors, while too limited studies used electric arc furnace slag (EAFS) for this purpose. The EAFS is a type of steel slag, which can be produced when scrap steel is melted. The preliminary usage of EAFS as a precursor in the geopolymer system has not been sufficiently highlighted. To make this come true, the current procedure employed EAFS as a precursor material for the geopolymeric system. Due to superior properties, EAFS was partially replaced with 10–50 wt% pozzocrete (Pz). Two different types of alkaline activators, NaOH and Na2CO3, were used to activate EAFS slurries supported by Pz. The results indicated that the optimal ratio of Pz to be replaced by EAFS to achieve the target properties varies according to the type of activator. The inclusion of 10% Pz exhibited maximum compressive strength when Na2CO3 was used, whilst 50% Pz exhibited maximum compressive strength when NaOH was used. The coexistence between N-A-S-H from Pz and C-(A)-S-H gel from EAFS is the main reason for the enhanced strength.

Hydration behavior and cementitious properties of steel slag: From an early age to a long-term

In China, steel slag as a solid waste caused land occupation and environmental pollution, and its utilization ratio is relatively low. To increase the utilization field and ratio of steel slag, hydration behavior and cementitious properties of three types of steel slag were investigated and compared based on test results from an early age to a long-term via multiple techniques. Experimental results suggested that steel slag showed a strong latent hydraulic activity at a later age, and the mechanical strength of steel slag paste specimens (w/b=0.3) could reach 15 MPa at 360 days. Cementitious properties of steel slag were primally depended on the hydration of calcium silicate (C3S and C2S), calcium aluminate (ferrite), glassy phase in steel slag, especially for calcium silicate. The sum amount of calcium silicate in used steel slag was approximately from 21% to 28%, and the amount of C2S was significantly greater than that of C3S. The hydration of C2S and glassy phase resulted in the continuous increase in bound water content of steel slag, and a certain content of C2S still existed in pastes at 360 days. The mechanical strength of steel slag pastes markedly increased at a later age due to more hydrates formed in the microstructure.

Evaluation of saturation in cemented slags with P-wave velocities

The application of the circular economy concept to construction engineering and to transportation geotechnics, brings several challenges associated to the use of non-conventional artificial materials. Steel slags can replace natural raw materials, but a thorough mechanical characterisation is needed to assure an adequate behaviour and quality control parameters. The focus of this paper is a mixture of two types of steel slags (a reducing slag and an oxidizing slag) from electric arc furnace steel production. The mixture has cementing properties, mainly due to the reducing slag, being stable in water after compaction. Due to its high stiffness and reduced permeability, the evaluation of the degree of saturation of the mixture using the conventional Skempton parameter B is not very reliable. In this work, P wave velocity measurements in specimens with different cementation levels (given by amount of reducing slag and curing time) and soaked conditions (before and after submersion) were compared. In addition, the elastic shear stiffness evolution with time obtained by S wave velocity measurements demonstrated a clear increase in stiffness with curing time especially in soaked specimens. The aim of the paper is thus to discuss the advantage of P waves to identify full saturation in stiff specimens that harden with time and water. It was found that it is very difficult to evaluate the degree of saturation of a highly cemented specimen, either with the B value or with the P-wave velocities. However, the usual mechanical evaluation by triaxial compression tests is still valid provided that suction is low.

Chemical, mineralogical, microstructural and engineering properties of tropical soils stabilised with the combined and individual use of different types of steel slag

The combined use of electric arc furnace slag fines (EAFSF) and ladle furnace slag fines (LFSF) for soil stabilisation was not evaluated in previous works. Previous studies reported limited information on the microscale behaviour of steel slag materials used in soil stabilisation. This work evaluated synergistic effects provided by the combination of EAFSF and LFSF on the stabilisation of clayey and sandy soils. It provided a detailed microscale analysis of raw materials and slag-soil mixes with scanning electron microscopy, X-ray diffraction, X-ray fluorescence, Raman spectroscopy, thermogravimetric analysis, and derivative thermogravimetry. Their compaction behaviour, unconfined compressive strength (UCS), CBR index, swelling, and resilient modulus were also determined. Filler effects, cementitious, pozzolanic, and ion-exchange reactions were discussed. A positive synergistic behaviour was observed when combining 10% LFSF and 5% EAFSF (by soil weight), which provided a structural arrangement that provided increases in UCS and CBR up to 651% and 1500%, respectively

The investigation on properties of sodium sulfate-activated mortar incorporating steel slag with various replacement ratio and particle size

The alkali-activated materials are alternatives for replacing Portland cement to manufacture concrete products, which has benefits on reducing carbon dioxide (CO2) emission and supporting the development of green sustainable construction. The combined use of steel slag (SS) and alkali activator (AA) to make alkali-activated concrete not only reuse the industrial waste but also improve the activity of SS. There are many types of chemicals can be used as AA, such as sodium silicate, sodium hydroxide, sodium carbonate and sodium sulfate (SST). In this study, SST was chosen as the AA, and the performance of alkali-activated mortar incorporating SS from 0 to 12.5% of Portland cement by mass, activated by SST with the dosage varying from 0 to 3% of cement by mass, was investigated. In addition, two types of SS, of which the particle sizes are less than 75 μm and 150 μm, were used to manufacture alkali-activated SS mortar. Flow table test, compressive strength test and flexural strength test were conducted to evaluate the fresh and hardened properties of alkali-activated steel slag (AA-SS) mortar. Response surface methodology (RSM) was used in this study as an analysis method. As result, the addition of SS tends to decrease the strength of mortar, while the addition of SST could lead to the increase in the strength of mortar.

Improvement of desulfurization efficiency of Al-rich ladle furnace refining slag with an aqueous carbonation method by hydrothermal or ultrasound pretreatment.

Ladle furnace (LF) slag is a type of steel slag, which has limited applications due to its high S content. Aqueous carbonation is a prospective method for desulfurization of the LF slag. However, the Al-rich LF raw slag has very low desulfurization efficiency with carbonation method. This study investigated the improvement of desulfurization efficiency of the Al-rich LF slag with carbonation method by hydrothermal (HP) or ultrasound pretreatment (UP). The results showed that C3AHX was formed in pretreated slags because of C12A7 hydration, which could remove part of S. After carbonation, most of the C3AHX in pretreated slags produced crystalline CaCO3 bonded by amorphous Al(OH)3 (the other reaction product) in 10min. In the carbonation process, S removal was mainly determined by carbonation efficiency. The S content was reduced to about 0.40% for the pretreated slags from 1.04% in the raw slag. By contrast, the S content was reduced to only 0.93% for slag without pretreatment under the same carbonation conditions. The possible reason of the improvement of desulfurization efficiency by HP or UP was the formation of thin plate-like C3AHx, which increased the surface area available for carbonation reaction. The UP slag presented slightly lower S content than the HP slag because high ultrasound energy increased the reactivity of Ca2SiO4.

Study on Preparation and Performance of Steel Slag Asphalt Mixture Based on Steel Slag Aggregate

The comprehensive utilization of steel slag has always been a worldwide problem. Under the background of vigorous development of highways in China, the application technology of steel slag in asphalt concrete will make the steel slag resources hopefully get a large number of reasonable utilization. Based on the application of steel slag in asphalt concrete, the basic physical and chemical properties of different types of steel slag were investigated. The blast furnace slag was used as the aggregate to prepare the asphalt mixture. The mixture was tested by research and test. The uniaxial compression test and the indirect tensile test were used to evaluate the low temperature crack resistance and fatigue resistance. The test results show that the surface texture of steel slag is rough and the embedding effect is good, which is beneficial to enhance the adhesion with asphalt and improve the shear resistance. The steel slag asphalt mixture has good low temperature deformation ability and small expansion ratio, which can be paved to meet the driving conditions. Required asphalt concrete pavement.

Properties of Steel Slag and Stainless Steel Slag as Cement Replacement Materials: A Comparative Study

To enhance the understanding about the utilization of steel slags as a cementitious material, we comparatively studied the chemical, mineralogical and morphological properties of two types of steel slag; basic-oxygen-furnace carbon slag (BOF C) and electric-arc-furnace stainless steel slag (EAF S). Moreover, we studied the standard consistency, setting time and the effect of the slag replacement ratios on the fluidity and compressive strength of blended cement mortar. The experimental results showed that BOF C had higher alkalinity, higher pH value and more hydraulic phases than EAF S. Both types of slag showed water reduction effect due to its high fineness. Neat BOF C paste showed flash set and acceleration in the initial setting time of blended cement especially at high slag proportions. However, EAF S prolonged the setting time of blended cement even at low slag proportions. The pH values for blended cement contained 50% BOF C or EAF S were lower than those of pure cement paste. Despite of slag type, compressive strength gradually decreased with increasing slags content. The strength of BOF C mortar was higher than that of EAF S mortar with the same replacement ratio for the same age. Slag activity index demonstrated that BOF C and EAF S conformed to the Chinese National Standard (GB/T 20491-2006) requirements for steel slag as grade one and grade two, respectively.

Dissolution of steel slags in aqueous media.

Steel slag is a major industrial waste in steel industries, and its dissolution behavior in water needs to be characterized in the larger context of its potential use as an agent for sequestering CO2. For this purpose, a small closed system batch reactor was used to conduct the dissolution of steel slags in an aqueous medium under various dissolution conditions. In this study, two different types of steel slags were procured from steel plants in India, having diverse structural features, mineralogical compositions, and particle sizes. The experiment was performed at different temperatures for 240h of dissolution at atmospheric pressure. The dissolution rates of major and minor slag elements were quantified through liquid-phase elemental analysis using an inductively coupled plasma atomic emission spectroscopy at different time intervals. Advanced analytical techniques such as field emission gun-scanning electron microscope, energy-dispersive X-ray, BET, and XRD were also used to analyze mineralogical and structural changes in the slag particles. High dissolution of slags was observed irrespective of the particle size distribution, which suggests high carbonation potential. Concentrations of toxic heavy metals in the leachate were far below maximum acceptable limits. Thus, the present study investigates the dissolution behavior of different mineral ions of steel slag in aqueous media in light of its potential application in CO2 sequestration.

Evaluations of Performance and Thermal Properties in Porous Asphalt Concrete Containing Steel Slag

In this study, porous asphalt concrete (PAC) containing different levels of steel slag are constructed to evaluate the performance and the thermal properties of the pavement. There will be two types of steel slag used in this study, they are Baosteel's Slag Short Flow (BSSF) slag and blast oxygen furnace (BOF) slag. The previous research proved that using steel slag as aggregate can improve the performance of asphalt pavement. However, steel slag is able to store heat so that using steel slag as aggregates will affect the thermal properties of the pavement. The goal of this studies is to find the optimum percentage of steel slag as subtitutes for coarse aggregates in porous asphalt based on performance and thermal properties.

Road material basis in dredged sediment and basic oxygen furnace steel slag

The aim of this works is to promote the co-valorisation and shown the important potential of waste in civil engineering materials.The paper presents the experimental methodology to develop a formulation of road material made from dredged sediment treaty with steel slag, a co-product of the steel industry. The mixes destined to improve the mechanic performance of formulated material.In this study two formulations are considered and compared, where two type of steel slag are used to treat dredged sediment. The methodology of this study consists to three steps (Fig. 2). First, a characterisation study has helped understand the physical–chemical and mechanical properties of used materials. We explored also the environmental characteristics by exploration of potential pollution of used materials. The second step consists to develop a method to determine the optimal mix between sediment and steel slag in terms of packing density of mix. In this part, we studied the packing density of the different mixtures to determine the proportions of mixes with maximum packing density. The experimental results were compared with literature model to prediction of packing density. The last part of this study consists to study the mechanical behaviour and durability of the final materials. In this part, we study the mechanical behaviour in short-term and long-term and durability aspect.

Study on Characteristics of Steel Slag for CO2 Capture

Steel slag is a kind of alkaline mixture and considered to be a potential CO2 adsorbent. In this work, the CO2-trapping characteristics of two types of steel slag, basic oxygen furnace (BOF) steel ...

Changes in mineralogical and leaching properties of converter steel slag resulting from accelerated carbonation at low CO 2 pressure

Steel slag can be applied as substitute for natural aggregates in construction applications. The material imposes a high pH (typically 12.5) and low redox potential (Eh), which may lead to environmental problems in specific application scenarios. The aim of this study is to investigate the potential of accelerated steel slag carbonation, at relatively low pCO 2 pressure (0.2 bar), to improve the environmental pH and the leaching properties of steel slag, with specific focus on the leaching of vanadium. Carbonation experiments are performed in laboratory columns with steel slag under water-saturated and -unsaturated conditions and temperatures between 5 and 90 °C. Two types of steel slag are tested; free lime containing (K3) slag and K1 slag with a very low free lime content. The fresh and carbonated slag samples are investigated using a combination of leaching experiments, geochemical modelling of leaching mechanisms and microscopic/mineralogical analysis, in order to identify the major processes that control the slag pH and resulting V leaching. The major changes in the amount of sequestered CO 2 and the resulting pH reduction occurred within 24 h, the free lime containing slag (K3-slag) being more prone to carbonation than the slag with lower free lime content (K1-slag). While carbonation at these conditions was found to occur predominantly at the surface of the slag grains, the formation of cracks was observed in carbonated K3 slag, suggesting that free lime in the interior of slag grains had also reacted. The pH of the K3 slag (originally pH ± 12.5) was reduced by about 1.5 units, while the K1 slag showed a smaller decrease in pH from about 11.7 to 11.1. However, the pH reduction after carbonation of the K3 slag was observed to lead to an increased V-leaching. Vanadium leaching from the K1 slag resulted in levels above the limit values of the Dutch Soil Quality Decree, for both the untreated and carbonated slag. V-leaching from the carbonated K3 slag remained below these limit values at the relatively high pH that remained after carbonation. The V-bearing di-Ca silicate (C2S) phase has been identified as the major source of the V-leaching. It is shown that the dissolution of this mineral is limited in fresh steel slag, but strongly enhanced by carbonation, which causes the observed enhanced release of V from the K3 slag. The obtained insights in the mineral transformation reactions and their effect on pH and V-leaching provide guidance for further improvement of an accelerated carbonation technology.

Chemical, Mineralogical, and Morphological Properties of Steel Slag

Steel slag is a byproduct of the steelmaking and steel refining processes. This paper provides an overview of the different types of steel slag that are generated from basic-oxygen-furnace (BOF) steelmaking, electric-arc-furnace (EAF) steelmaking, and ladle-furnace steel refining processes. The mineralogical and morphological properties of BOF and electric-arc-furnace-ladle [EAF(L)] slag samples generated from two steel plants in Indiana were determined through X-Ray Diffraction (XRD) analyses and Scanning Electron Microscopy (SEM) studies. The XRD patterns of both BOF and EAF(L) slag samples were very complex, with several overlapping peaks resulting from the many minerals present in these samples. The XRD analyses indicated the presence of free MgO and CaO in both the BOF and EAF(L) slag samples. SEM micrographs showed that the majority of the sand-size steel slag particles had subangular to angular shapes. Very rough surface textures with distinct crystal structures were observed on the sand-size particles of BOF and EAF(L) slag samples under SEM. The characteristics of the steel slag samples considered in this study are discussed in the context of a detailed review of steel slag properties.

Recycling of industrial waste and performance of steel slag green concrete

Workability and mechanical properties of steel slag green concrete with different types of steel slag and different dosages of admixtures were investigated. The effectiveness of steel slag powder on suppressing alkali aggregate reaction (AAR) expansion was assessed using the method of ASTM C441 and accelerated test method. Experimental results show that mechanical properties can be improved further due to the synergistic effect and mutual activation when compound mineral admixtures with steel slag powder and blast-furnace slag powder are mixed into concrete. In addition, about 50% decrease in expansion rate of mortar bars with mineral admixtures can be achieved in AAR tests. Mineral admixtures with steel slag powder as partial replacement for Portland cement in concrete is an effective means for controlling expansion due to AAR.

Workability and Strength Characteristics of High Performance Concrete with Steel Slag Admixture

Workability, mechanical properties and durability of concrete can be greatly improved with the advanced mineral admixtures such as steel slag powder. The workability and mechanical properties of steel slag concrete with different types of steel slag and different dosage of admixtures are studied. The experimental results showed the effect of steel slag powder on concrete performance. When compound mineral admixtures with steel slag powder and blast-furnace slag powder are mixed into concrete, the performance of concrete can be improved further due to the synergistic effect and mutual activation.

ABSORPTION OF LEAD IONS BY VARIOUS TYPES OF STEEL SLAG

Steel slags are the by products of steel industries, which forms during reduction process of iron melting. The chemical composition of it changes depending to the melting procedure. Its mineralogical composition also varies based on the cooling procedure. Two different types of steel slag were used as absorbing bed for various concentrations of Pb 2+ ions in the form of lead chloride, and the concentrations of lead ions were measured in the effluent by atomic absorption spectroscopy. When Electric Arc Furnace slag (EAFS) which is a basic crystalline slag was used in the presence of various concentrations of Pb 2+ , ranging from 2mg/lit up to 10 mg/lit. The concentration of lead ions dramatically decreased in the first thirty 30 minute and the remaining ions were absorbed up to 48 hours that the reaction was continuing but with slower rate. Almost the same thing happened when granulated blast furnace slag (GBFS) which is also a basic slag but in the amorphous mineralogical form, was used as the absorbing bed. The extent of ion removal from the solution was much lower compared to EAFS. Based on the results of this study, both types of slags can be used as industrial filters for reduction of lead ions from industrial waste waters.

Characteristics of steel slag under different cooling conditions

Four types of steel slags, a ladle slag, a BOF (basic oxygen furnace) slag and two different EAF (electric arc furnace) slags, were characterized and modified by semi-rapid cooling in crucibles and rapid cooling by water granulation. The aim of this work was to investigate the effect of different cooling conditions on the properties of glassy slags with respect to their leaching and volume stability. Optical microscopy, X-ray diffraction, scanning electron microscope and a standard test leaching (prEN 12457-2/3) have been used for the investigation. The results show that the disintegrated ladle slag was made volume stable by water granulation, which consisted of 98% glass. However EAF slag 1, EAF slag 2 and the BOF slag formed 17%, 1% and 1% glass, respectively. The leaching test showed that the glass-containing matrix did not prevent leaching of minor elements from the modified slags. The solubility of chromium, molybdenum and vanadium varied in the different modifications, probably due to their presence in different minerals and their different distributions.