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Arsenic, which is widespread in receiving environments through natural and anthropogenic sources, is one of the most important problems encountered in ground and surface waters in terms of public health in recent years due to its toxic and carcinogenic properties. In this study, the adsorptive removal of arsenic was investigated by using low cost and environmentally-benign adsorbents obtained from natural and waste materials. For this purpose, pumice was chosen as natural material, red mud and steel slag were chosen as waste material. The influence of contact time and adsorbent dosage was investigated using batch tests. 50-95% arsenic removal was achieved with tested adsorbents. Modified Freundlich isotherm was found to provide the best fits to experimental data. Experimental studies have shown that steel slag is the most effective adsorbent in arsenic removal and has a maximum adsorption capacity of 3.058 mgAs g-1. The high arsenic adsorption capacity of the steel slag can be attributed to the high content of iron and calcium oxide. The present study results show that steel slag can be good alternative to commercial activated carbons for the adsorptive removal of arsenic. Moreover, the reuse of this waste material will also provide a double-side environmental benefit in an inexpensive and effective way., Doğal ve antropojenik kaynaklar yoluyla alıcı ortamlarda yaygın halde bulunan arsenik, toksik ve kanserojen özelliklerinden dolayı halk sağlığı açısından son yıllarda yer altı ve yer üstü sularında karşılaşılan en önemli sorunlardan biridir. Bu çalışmada, doğal ve atık materyallerden elde edilen düşük maliyetli ve çevre dostu adsorbentler kullanılarak arseniğin adsorptif giderimi araştırılmıştır. Bu amaçla doğal malzeme olarak pomza, atık malzeme olarak kırmızı çamur ve çelikhane cürufu seçilmiştir. Temas süresinin ve adsorbent dozunun etkisi kesikli deneyler yapılarak araştırılmıştır. Test edilen adsorbetler ile %50-95 arasında arsenik giderimleri sağlanmıştır. Deneysel dataların modifiye Freundlich izoterm modeline uyduğu belirlenmiştir. Deneysel çalışmalar, çelikhane cürufunun arsenik gideriminde en etkili adsorbent olduğunu ve 3.058 mgAs g-1 maksimum adsorpsiyon kapasitesine sahip olduğunu göstermiştir. Çelikhane cürufunun yüksek arsenik adsorpsiyon kapasitesi, içerisinde yüksek oranlarda bulunan demir oksit ve kalsiyum oksite bağlanabilir. Mevcut çalışma sonuçları, çelikhane cürufunun arsenik gideriminde ticari aktif karbonlara iyi bir alternatif adsorbent olabileceğini göstermektedir. Bununla birlikte bu atık materyallerin tekrar kullanılması ile atık bertaraf probleminin önüne geçilecek ve ucuz ve etkili bir şekilde çevresel olarak çift taraflı fayda sağlanmış olacaktır.

Millimeter-scale magnesian refractory granules were found to be a unique magnesian-expansive component in steel slag. To systematically study the effects of these granular magnesian-expansive components on the volume stability of cement-based materials containing steel slag, an investigation of their existing forms and influence on the volume stability was conducted in this paper. The various-sizing waste–magnesium–chromate-based refractory brick (Mg-Cr brick) granules and different (FeO + MnO)/MgO ratios’ synthetic MgO·xFeO·yMnO ternary solid solutions granules were adopted to simulate magnesian-expansive granules by partially replacing manufactured sand in mortar. The 100 °C–3 h boiling and 213 °C–2 MPa–3 h autoclaving treatments were adopted as volume stability testing methods. The results indicated that whether Mg-Cr brick or MgO·xFeO·yMnO solid solution, the concentration of expansive stress and the anisotropy expansion came with the granular size rising weakening the volume stability of cement-based materials which contained magnesian-expansive granules, significantly. Meanwhile, this phenomenon resulted in the ineffectiveness of the single linear expansion rate when assessing the qualification of volume stability. Furthermore, it also changed the mortars’ failure mode from “muddy damage” to “break into blocks”. Especially, there is no volume stability issue when the MgO·xFeO·yMnO satisfied (FeO + MnO)/MgO ≥ 1.00. Considering the significant effect of the granular magnesian-expansive components on the volume stability of cement-based materials containing steel slag, it is imperative to enhance the detection of both MgO content and mineral existing forms in steel slag in practical applications. For recommendation, the threshold value of conducting autoclaved volume stability testing on steel slag should be set at MgO ≥ 3%. Furthermore, the qualification cannot be judged by the single linear expansion rate; the specimens’ appearance integrity and strength loss should also be noted.

For further resource utilization of solid waste steel slag and the reduction in biodiesel production costs, this study used steel slag as a carrier to synthesize a CaO-CeO2/slag solid base catalyst for the effective transesterification of palm oil into fatty acid methyl esters (FAMEs). The synthesis involved a two-step impregnation of steel slag with nitrate of calcium and cerium and thermal activation at 800 °C for 180 min. Then, the catalysts’ textural, chemical, and CO2 temperature-programmed desorption properties were characterized. The catalytic activity depended highly on the ratio of Ca-Ce to steel slag mass; the CaO-CeO2/slag-0.8 catalyst showed outstanding performance. Characterization showed that the surface area and total basicity of the Ca-Ce/slag-0.8 catalyst were 3.66 m2/g and 1.289 mmol/g, respectively. The reactivity results showed that FAMEs obtained using 7 wt.% catalyst, 9:1 of methanol-to-palm-oil molar ratio, 180 min reaction duration, and 70 °C reaction temperature was optimum (i.e., 95.3% yield). In addition, the CaO-CeO2/slag-0.8 catalyst could be reused for at least three cycles, retaining 91.2% of FAMEs yield after n-hexane washing. Hence, the catalyst exhibits an excellent potential for cost-effective and environmentally friendly biodiesel production.

Crude steel production in China exceeds 1 billion tons per year, and steel slag production accounts for 10%–15% of the crude steel mass. Although slag presents certain hydration activity, it is still difficult to be used as a building material because the particles contain a large amount of active calcium oxide and magnesium oxide, which are easy to hydrate and expand besides presenting low stability. The heap stock is increasing at a rate of 80 Mt/a because of the limitation of application scenarios. Moreover, every 1 ton of crude steel is associated with an emission of 1.8 tons of carbon dioxide (CO2), which becomes a greenhouse gas, because it cannot be reused at the moment. In this investigation, CO2 was used to cure steel slag particles, and the coupling mineralization reaction between them was used to convert active calcium oxide and magnesium oxide in steel slag into carbonate forms and, thus, allow the processing of steel slag particles into fine building aggregate. Two particle size ranges of 0.6–2.36 and 2.36–4.75 mm were selected as representative particle sizes. Mineralization was carried out under a temperature of 25 °C, relative humidity of 75%, a CO2 concentration of 20%, and a time of 24 h. The carbon fixation rate of steel slag was 9.68%. The quality of steel slag fine aggregate as a product met the GB/T 14684-2011 construction sand grade II standard. The application of this technology is expected to improve the stability of steel slag particles, the utilization rate as a building material, and the resource utilization level of CO2. It is expected to realize the full, high-value-added resource utilization of steel slag and CO2 absorption and solve the supply shortage problem of fine aggregate for construction in China, which has potential economic and environmental benefits.

Carbon capture and storage (CCS) technology can reduce CO2 emissions by 85 to 95% for power plants and kilns with high CO2 emissions. Among CCS technologies, carbon dioxide capture using steel slag is a method of carbonating minerals by combining oxidized metals in the slag, such as CaO, MgO, and SiO2, with CO2. This study assessed the amount of CO2 captured and the sequestration efficiency in operating a mineral carbonation plant with a CO2 capture capacity of 5 tons/day by treating the exhaust gas from a municipal waste incinerator and identified the characteristics of the mineral carbonation products. As a result, the average concentration of CO2 in the inflow and outflow gas during the reaction time was 10.0% and 1.1%, respectively, and the average CO2 sequestration efficiency was 89.7%. This resulted in a conversion rate of CaO of > 90%. This study manifested that mineral carbonation products are more stable than steel slag as a construction material and are effective at sequestering CO2 by forming chemically stable CaCO3.

In order to investigate the influence of SiC on the composition and structure of mixed slag (blast-furnace slag: steel slag = 1:9), the chemical composition, equilibrium-phase composition, and microscopic morphological characteristics and elemental distribution in the microscopic region of the SiC-reagent-tempered slag samples were analyzed by X-ray diffractometer (XRD), FactSage7.1 thermodynamic analysis software, scanning electron microscope, and energy spectrum analyzer. It was found that the main physical phases of the tempered slag samples were magnesia–silica–calcite (Ca3Mg(SiO4)2, C3MS2), calcium–aluminum yellow feldspar (Ca2Al2SiO7, C2AS), C2S, and iron alloy. Theoretical calculations suggest that the experimental temperature should be higher than 1500 °C to facilitate the combination of P5+ with Fe and Mn in the liquid phase to form an alloy, reduce the P5+ content in the tempered slag, and create conditions for the self-powdering of the conditioned slag. The doping of the SiC reagent can increase the liquid phase line temperature and reduce the binary basicity in the liquid phase; the liquid phase line temperatures were 1150 °C, 1200 °C, and 1300 °C and the basicities in the liquid phase were 4.68, 4.13, and 3.10 for the doping amounts of 3%, 4%, and 5% of the SiC reagent, respectively. The mixed slag doped with 4% SiC reagent achieves self-powdering and reduction of ferroalloys during the air-cooling and cooling processes, realizing the purpose of “resource utilization” of blast-furnace slag and steel slag.

A continuous treatment process using steel slag powder including foam drying and carbonation processes (termed the SSFD-C method) is a novel technology previously developed in our laboratory. It has achieved the first application of carbonation solidification technology to recycle marine dredged material with high moisture content. The aim of this study is to investigate CO2 uptake and performance regulation in the preparation of carbonated eco-aggregates (CEAs) from dredged soils processed using the SSFD-C method. Steel slag and lime hydrate independently contribute to the strength of CEAs. However, the influence they exert on CO2 uptake, along with other properties, such as pH values and water absorption of CEAs, remains unclear. Furthermore, it is important to clarify whether the soluble silica in a CEA originates from dredged soil or steel slag, as a CEA has the potential to provide silica nutrients to plants. The findings indicated that within the initial three hours of carbonation, the strength of CEAs could approximate 65% of the ultimate stable strength. The moisture absorption for CEAs was noted to be in the 26–30% range. Carbonation over a 24 h period can lower the pH of the CEA to less than 10, and the carbonation reaction can penetrate the core of the 10–15 mm CEA pellets. Carbonation of the lime hydrate fraction was more favorable to increase the CO2 uptake of the CEA, and carbonation of the steel slag fraction was more favorable to decrease the pH value and water absorption of the CEA. The water-soluble silicon of the CEA was found to have been mainly derived from steel slag, while it was established that carbonation could increase the water-soluble silicon content of the CEA by 5–8 times. The result of this study could provide theoretical guidance for regulating the performance of CEAs.

In this paper, a kind of steel slag, concrete-filled double-skin steel tube (CFDST) T-joint is proposed to promote sustainable structural development. In order to examine the seismic performance of the steel slag CFDST T-joint, a series of hysteresis experiments were carried out on 4 CFDST T-joints with the main pipe under axial compression load and the brace pipe subjected to cyclic axial loading. The seismic performance of the CFDST T-joint was experimentally investigated in terms of the failure mode, load–displacement hysteresis relationship, stiffness degradation, energy dissipation and ductility. The effects of the hollow ratio and the steel slag concrete of the CFDST main pipe on the seismic performance of CFDST T-joint specimens were compared and analyzed. The experimental results show that the failure modes of the CFDST T-joint mainly included two kinds of failure, with those being main pipe fracture and joint area compression-bending failure. The seismic performance of the joints could be improved with a 12% ultimate bearing capacity and 54% ultimate deformation capacity with the hollow ratio of the CFDST main pipe increasing from 0 to 0.5. The seismic performance of the joints could be improved with a 54% ultimate deformation capacity by filling the steel slag concrete with a 0.5 hollow ratio.

Steel slag (SS) has been largely discharged but little utilized, causing an environmental problem in China. In this paper, SS-based composite cementitious materials with high strength were prepared by the high volume of SS (≥40%), granulated blast-furnace slag (GBFS), fly ash (FA), flue gas desulfurization gypsum (FGDG) and cement to promote the effective utilization of SS. The hydration and hardening properties were studied through setting time, compressive strength, length change, isothermal calorimetry (IC), X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), and scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS) tests. The results show that SS-based composite cementitious material exhibited a lower hydration heat release, an appropriate setting time, and volume stability. The SS cementitious material with 40% SS could obtain high strength of over 65 MPa at 28 days and 80 MPa at 90 days. The strength value of > 60 MPa is present in the binder, with 50% SS at 56 days. GBFS promotes hydration reactions and the formation of AFt and C-(A)-S-H gel, thus enhancing compressive strength. FA has a beneficial effect on later strength. The small and fine pore structures contribute to the development of strength. The main hydration products of SS composite cementitious materials are C-(A)-S-H gel, and ettringite (AFt), with less Ca(OH)2. The C-(A)-S-H gel with a lower Ca/Si ratio and a higher Al/Ca ratio in cementitious material, promotes mechanical properties.

This study intends to predict the long-term skid resistance of steel slag asphalt mixture (SSAM) from the mineral composition of the aggregates. The polished stone value (PSV) and mineral composition of the aggregates were assessed using the accelerated polishing test and X-ray diffraction, respectively. The hardness (H) and surface texture richness (STR) of the aggregates were calculated from the mineral composition of the aggregates, and then a multivariate linear model was established between PSV and H and STR. The British pendulum number (BPN) and three-dimensional morphology of the SSAM were then evaluated using a British pendulum and a pavement laser scanner, respectively. Finally, an exponential relationship was established between BPN, aggregate PSV, and various aggregate amounts of SSAM. The results show that steel slag with H, STR, and PSV was better than natural aggregates and can significantly improve the skid resistance of pavement, but the relationship between steel slag content and long-term skid resistance of SSAM was not linear, and SSAM with 50% steel slag content had the best skid resistance. The mathematical model developed can predict the long-term skid resistance of SSAM from the mineral composition of the aggregates. The model can be used by designers to predict the long-term skid resistance of steel slag asphalt pavements at the design stage and thus better determine the proportion of steel slag to other aggregates.

Steel slag has been proven to be an effective environment remediation media for acid neutralization, and a potential aid to mitigate acid mine drainage (AMD). Yet its acid neutralization capacity (ANC) is frequently inhibited by precipitate after a period of time, while the characteristics of the precipitate formation process are unclear yet. In this study, ANC for basic oxygen steel slag was conducted by neutralization experiments with dilute sulfuric acid (0.1 M) and real AMD. Some partially neutralized steel slag samples were determined by X-ray diffraction (XRD), scanning electron microscopy combined with an energy dispersive spectrometer (SEM-EDS), and N2 adsorption tests to investigate the potential formation process of the precipitate. The results indicated that Ca-bearing constitutes leaching and sulfate formation were two main reactions throughout the neutralization process. A prominent transition turning point from leaching to precipitate was at about 40% of the neutralization process. Tricalcium silicate (Ca3SiO5) played a dominant role in the alkalinity-releasing stage among Ca-bearing components, while the new-formed well crystalline CaSO4 changed the microstructure of steel slag and further hindered alkaline components releasing. For steel slag of 200 mesh size, the ANC value for the steel slag sample was 8.23 mmol H+/g when dilute sulfate acid was used. Neutralization experiments conducted by real AMD confirmed that the steel slag ANC was also influenced by the high contaminants, such as Fe2+, due to the hydroxides precipitate reactions except for sulfate formation reactions.

The purpose of this study was to evaluate the feasibility of the large-scale application of steel slag (SL) in subgrade. Subgrade materials with three kinds of SL proportions were first prepared. Then, a compaction test, liquid-plastic limit combined-measurement test, and a California bearing ratio (CBR) test were applied to determine the best proportion between SL and intact soil (S), i.e., SL/S. Subsequently, static and dynamic tests and a volume stability test were carried out for soil mixed with SL at the optimum proportion (SSL). In addition, a composition analysis of infiltration fluid and a permeability test of SSL were performed. The test results showed that compared to S, the physical properties of SSL were significantly improved, especially the liquid-plastic limit, as well as the soil water stability. The optimum proportion of SL was determined as 50% of soil by mass. At the optimum proportion, SSL had the highest CBR value of 60%, which had both economic and engineering compaction performance, leading to a large-scale utilization rate of SL. The static and dynamic characteristics showed that the addition of SL would greatly improve the shear strength and dynamic modulus of soil, mainly expressed as the increase of internal friction angle. The volume stability of SSL could also meet the requirements of the Chinese specification. After adding 2% cement, the strength and stability of SSL was further improved. In addition, the environmental impact test proved that the infiltration liquid did not pollute surface water nor underground secondary water. Although the permeability coefficient of SSL with the optimum proportion of 50% was higher than that of pure soil, it still belonged to the normal value of clay and silty clay, and good impermeability would ensure the controllability of potential trace elements. Based on the test results of mechanical properties and environmental impact, SSL proved to have the potential for green road material engineering properties. This study proposes a reliable and practical method to promote the utilization of steel slag.

In this study, the oxidation characteristics of elemental mercury were assessed based on the input gas environment, temperature, and particle size distribution of the steel slag. Experiments were performed at room temperature, 100 °C and 200 °C, under air and simulated gas environments. The oxidation reaction of elemental mercury was conducted using steel slag samples of 1 mm, 2.36 mm, and 4.75 mm at various conditions. From the basic characteristic analysis of the steel slag, it was found that the steel slag exhibits a similar composition to that of fly ash, and it can be utilized as an oxidizing agent. Results show that regardless of the temperature and the particle size distribution of steel slag, the oxidation reaction of elemental mercury rarely occurred in the air environment. However, in the case of the HCl gas environment, it was observed that the smaller the steel slag particle size, the stronger the oxidation reaction. It is believed that the oxidation efficiency of the steel slag increased as the contact area between the gas and particles increased. The oxidation reactivity was nearly two times higher in the temperature range of 100 °C to 200 °C than it was at room temperature. It is advised that further research be undertaken in order to determine the precise temperature range at which the oxidation reaction occurs.

Due to its environmental and economic advantages, the use of recycled materials in asphalt mixes is witnessing increased interest, where the properties of those mixes are significantly affected by the properties of the recycled materials in them. This paper discusses the results of an experimental study conducted to evaluate the performance of recycled asphalt mixtures made with reclaimed asphalt pavement aggregate (RAP). These mixtures were also prepared with two filler additives, namely steel slag (SS) and silica fume (SF), at four different percentages by weight of the aggregate. A total number of 234 mixtures were tested. The laboratory results indicated the effectiveness of using such additives as a filler material. The Marshall stability showed improvement for mixes prepared with steel slag ranging from 11.73 to 32.73 kN as the RAP level increased; the highest stability load was recorded for the 75% RAP with a 50% steel slag mix. On the other hand, the silica fume depicted variance in its strength, yet the maximum load value of 31.02 kN was for the 75% RAP with 100% silica fume. The use of steel slag in the presence of water decreased the stability results, while satisfying the ASTM standards.

Sathi kaplamalar, yeni yapılan yol üstyapılarında ve bakım-onarım amaçlı olarak yaygın olarak uygulanmaktadır. Ülkemizdeki yol ağının büyük kısmı sathi kaplama tabakasından oluşmaktadır. Sathi kaplamalar, temel tabakası üzerine püskürtülen bitüm yapıştırma veya astar tabakası üzerine agrega tabakasının tek kat veya çift kat serilip, sıkıştırılması ile uygulanabilen ekonomik bir kaplama tipidir. Bu kaplama tabakası, taşıtlar için kayma direnci yüksek ve düzgün bir yuvarlanma yüzeyi sağlamakta ve üstyapıyı trafik ve iklimin aşındırıcı etkilerinden korumaktadır. Bu çalışmada, sathi kaplama tipinin performansının incelenmesi ve geliştirilmesi amaçlanmaktadır. Bu kaplama tipi için özellikle agrega-bağlayıcı adezyonu önemlidir. Çalışmada, seçilen kaynaklardan temin edilen farklı tipteki agregaların (kalker, bazalt, gabro ve çelik cürufu) sathi kaplama tasarım performansları incelenmiştir. Bitüm-agrega aderansı ve soyulmaya karşı direncinin iyileştirilmesi için sönmüş kireç, uçucu kül ve yüksek fırın cürufu kullanılarak bulamaç yöntemi ile agrega yüzeyleri işleme tabi tutulmuş ve sathi kaplama tasarım performansına etkileri araştırılmıştır. Bu çalışma ile, sathi kaplama performansının iyileştirilmesi yanında, doğal kaynak kullanımının azaltılmasına yönelik çevreci ve daha ekonomik bir tasarım hedeflenmiştir. Bu amaçla, doğal agregalar yanında, dayanıklı bir yapıya ve pürüzlü bir yüzeye sahip olan demir-çelik cürufu agrega olarak kullanılmıştır. Laboratuvar çalışmasında kullanılan agregalara ait özellikler belirlenmiş ve sathi kaplama tasarım deneyleri gerçekleştirilmiştir. Agrega tipinin ve bazı fiziksel özelliklerinin sathi kaplama performansı üzerindeki etkisinin belirleneceği çalışmada, performansın iyileştirilmesinde bulamaç yöntemi ile agrega yüzeyine yapıştırılmış sönmüş kireç, uçucu kül ve yüksek fırın cürufunun sergilediği performanslar yaygın olarak kullanılan soyulma önleyici katkı (DOP) ile karşılaştırılmıştır. Doğal agregaların sathi kaplama şartname limitlerini genel itibariyle sağladığı, çelikhane cüruf agregasının sadece su emme değeri şartname limit değerin üzerinde olduğu belirlenmiştir. Sonuçlar, agregaların genel olarak sathi kaplamalarda kullanılabilmesi için soyulma önleyici katkıların kullanımının gerekliliğini göstermektedir. Vialit deney sonuçları karşılaştırıldığında kireç taşı ile bazalt agregalarının gabroya ve demir cürufuna göre çok daha iyi sonuçlar verdiği görülmüştür. Sönmüş kireç modifikasyonu agregaların soyulma direncini iyileştirmekte, gabro ve cüruf agregasında DOP’a göre daha etkili olduğu görülmektedir. Sönmüş kireç modifikasyonun sathi kaplama performansı üzerinde diğer katkılara göre daha etkili olduğu belirlenmiştir. Chip seals are widely applied in newly constructed road pavements and for pavement maintenance and repair. It is applied in most of the road network as a surface layer in Turkey. Chip seals are an economical type of pavement coating. This coating application consists of compacting the aggregate layer, which can be laid as a single or double layer on the bitumen bonding or prime coat. It provides a smooth rolling surface with high skid resistance for vehicles and protects the pavement from the destructive effects of traffic and climate. In this study, it is aimed to examine and improve the performance of chip seal. Aggregate bitumen adhesion are important for this surface coating type. In the study, the chip seal design performances of different types of aggregates obtained from selected sources (limestone, basalt, gabbro and steel slag) were investigated. In order to improve bitumen aggregate adherence and stripping resistance, aggregate surfaces were treated with slurry method using hydrated lime, fly ash and blast furnace slag and their effects on chip seal design performance were investigated. With this study, besides improving the performance of chip seal, an environmentally friendly and more economical design is aimed to reduce the use of natural resources. For this purpose, iron-steel slag, which has a durable structure and a roughly surface, was used as aggregate. The properties of the aggregates used in the laboratory work were determined and chip seal design tests were conducted. In the study, in which the effect of aggregate type and some physical properties on the chip seal performance were determined, the performances of hydrated lime, fly ash and blast furnace slag adhered to the aggregate surface by slurry method were compared with the commonly used anti stripping additives (DOP). It has been determined that natural aggregates generally meet the surface coating specification limits, and only the water absorption value of the steel slag aggregate is above the specification limit value. The results show that the use of anti-stripping additives is necessary for the aggregates to be generally used in chip seal. Vialit test results of limestone and basalt aggregates are much better than gabbro and steel slag. Hydrated lime modification improves the stripping resistance of aggregates and is more effective than DOP in gabbro and steel slag aggregates. It was determined that the hydrated lime modification was more effective on the chip seal performance than the other additives.

Cilj ovog rada istražiti izvedivost korištenja otpadne čelične zgure kao zamjenskog materijala za slojeve kolničke konstrukcije (nosive slojeve). Ovaj se otpad skladišti i odlaže na odlagalište na lokaciji za proizvodnju čelika u JORF LASFAR-u, u gradu El Jadida, Maroko. Prikupljeni su uzorci otpada koji su podvrgnuti standardnim ispitivanjima kako bi se utvrdila njihova fizikalna, kemijska, mineraloška i geotehnička svojstva. Nadalje, otpadna čelična zgura ne može se koristiti samostalno u slojevima kolničke konstrukcije zbog niskog udjela sitnog agregata. Prirodni materijal (otpad od drobljenja kamena) upotrijebljen je s otpadnom čeličnom zgurom kako bi se postigla zahtijevana granulometrijska krivulja. Napravljeno je ukupno pet različitih mješavina čelične zgure (SS) i prirodnog agregata (ST) u sljedećim omjerima (% SS: % ST): M1 (30:70), M2 (40:60), M3 (50:50), M4 (60:40), i M5 (70:30). Provedena su geotehnička i mehanička ispitivanja svake pojedinačne mješavine, uključujući i mješavine M4 i M5, kako bi se utvrdilo ispunjavaju li te mješavine uvjete da bi se koristile u gornjim nosivim slojevima. Mješavine oznaka od M2 do M5 također su imale svojstva koja su potrebna za materijal donjih nosivih slojeva. Na kraju je provedena analiza dimenzioniranja kolničke konstrukcije kako bi se dobila debljina slojeva koji sadrže formulirane mješavine, za koje je utvrđeno da su slične debljinama konvencionalnih materijala., This paper aims to investigate the feasibility of using steel slag waste as an alternative material for pavement layers (sub-base and base layers). This waste is stored and landfilled at a steel production site in JORF LASFAR, city of El Jadida, Morocco. Samples of the waste were collected and underwent standard tests to determine its physical, chemical, mineralogical, and geotechnical properties. Furthermore, the steel slag waste cannot be used alone in pavement layers because of the low fraction of fine aggregates. Additionally, a sterile raw material (rock crushing waste) was used with the steel slag waste to obtain the required particle size distribution. Five mixtures of steel slag (SS) and sterile (ST) were formulated using the following proportions (% SS: % ST): M1 (30:70), M2 (40:60), M3 (50:50), M4 (60:40), and M5 (70:30). Geotechnical and mechanical standard tests were conducted on each mixture, including the M4 and M5 mixtures, to determine whether they met the required properties for a material used in the base layer. M2 to M5 mixtures also had the necessary properties for the sub-base layer. Finally, a sizing study was performed to obtain the thickness of pavement layers containing the formulated mixtures, which were found to be close to those of conventional materials.

Acid mine drainage (AMD) which produced in the process of mining seriously pollutes the water resources and endangers the ecological environment due to its physicochemical characteristics, such as low pH, high salinity and high heavy metal concentrations. In recent decades, the treatment of AMD has become a key issue in the field of environmental protection. One important method of AMD treatment is adsorption method, and the selection of adsorbent is the key of this technique. Bentonite and steel slag are usually sintered at high temperatures to prepare bentonite–steel slag composite. AMD treatment with bentonite–steel slag composite, as a new adsorbent, is emerging as a promising treatment method by physical adsorption, ion exchange and chemical neutralization. The bentonite–steel slag composites mainly include bicomponent composite with bentonite–steel slag and multicomponent composite with bentonite–steel slag modifier. The author found that this important research question was rarely paid attention to, therefore, and the author combined with previous research and theories to promote the explanation of this problem. In this review, the technology of treatment of AMD with bentonite–steel slag composite is comprehensively discussed. Also, the role of its mechanism is also discussed in-depth. This paper provides a scientific reference on the remediation of contaminated environments.

This study investigates the pattern of influence of blast furnace slag tempering on the composition and structure of steel slag. The chemical composition, equilibrium phase composition, microscopic morphological characteristics and elemental composition of microscopic regions of steel slag and blast furnace slag modified by high temperature reconstruction were analyzed using X-ray diffractometer (XRD), FactSage7.1 thermodynamic analysis software, mineral phase microscopy and field emission scanning electron microscopy. The results show that blast furnace slag blending can promote the generation of a low melting point phase in the slag, as well as reducing its melting temperature and improving its high temperature kinetic conditions. On the one hand, the incorporation of blast furnace slag was found to promote the generation of C2S in the steel slag and improve its gelling activity. Notably, at 1400 °C, the C2S content (mass fraction) of steel slag modified with 15% high temperature reconstruction reached 39.04%, while that of unmodified steel slag at this temperature was only 16.92%, i.e., only 1/4 of the C2S content in the modified slag. On the other hand, the incorporation of blast furnace slag inhibited the generation of a-C2S-C3P and calcium ferrate minerals, refined the grains of calcium–aluminum yellow feldspar, reduced the alkalinity and promoted the generation of silicate phases with high hydration activity in steel slag.

The idea of this particular study is to utilize industrial waste materials in an effective manner so as to give strength to steel tubular columns. Composite construction using steel - concrete has emerged as one of the fastest methods of construction in India. The inherent advantage of the steel-concrete composite section lies in that the two principal elements - the steel and the concrete are normally used in a manner so that full potential of both may be realized and the best utilization of their respective properties can be made. In this paper, an attempt was made with steel tubular columns in-filled with plain concrete, partial replacement of fine aggregate by fly ash & quarry dust and coarse aggregate by rubber, slag from the steel industry, granite and construction & demolition (C&D) debris concrete. The column specimens are to be tested under axial compression to investigate the effects of industrial waste materials. The effects of the steel tube and the strength of concrete are examined. 24 specimens were tested with the strength of concrete as 20 MPa and D/t ratio 25.40. The columns were 114.3 mm in diameter and 4.5 mm in thickness are 300, 600 & 900 mm in length. Strength characteristics and failure modes are to be discussed. The test results are to be compared with the values predicted by Eurocode 4, Australian Standards and American Codes and new theoretical models will be suggested for the design. From the test results, it was observed that the load-carrying capacity of steel tubular columns in-filled with various industrial waste materials concrete is greater than the conventional concrete. Hence this research would give a solution for effective utilization of industrial waste materials such as rubber, granite, C&D debris, steel slag, fly ash and quarry dust in concrete.

Resumen La presente investigación se basó en la innovación y elaboración de una mezcla asfáltica en caliente (MAC), debido al deterioro prematuro de los pavimentos flexibles, y poca capacidad de cumplir con su vida útil. He aquí la necesidad de asegurar una buena calidad de materiales para la mezcla asfáltica y una búsqueda de nuevo material que sea capaz de dar mayor durabilidad y evitar un prematuro deterioro del pavimento. Se evaluó así la incorporación de escoria de acero para el diseño de MAC, con el objetivo de determinar la estabilidad y flujo de la mezcla asfáltica en caliente incorporando escorias de acero. Para esto, se empleó la metodología Marshall con un porcentaje de escoria de acero respecto al agregado grueso en 0% - 15% - 25% - 50% - 75%. Los resultados obtenidos, en cuanto a calidad de los agregados, cumplieron con los estándares de calidad. Se concluyó que la mezcla asfáltica modificada con la escoria de acero al 15% es la mejor combinación, de igual forma, este porcentaje cumple para tránsito liviano, mediano, al 25% - 50% - 75% solo cumplen para transito liviano. Se logró aumentar la estabilidad y flujo de la mezcla asfáltica al incorporar hasta un máximo de 25% para una MAC respecto a la mezcla de control. Abstract The present investigation was based on the innovation and elaboration of a hot asphalt mix (HMA) due to the premature deterioration of flexible pavements, and low capacity to fulfill its useful life. Then, it is recognized the need to ensure a good quality of materials for the asphalt mix and a search for a new material that can give greater durability and avoiding premature deterioration of the pavement. Thus, the incorporation of steel slag for the HMA design was evaluated with the objective to determine the stability and flow of the hot asphalt mixture incorporating steel slags. To achieve this, the Marshall methodology was developed with a percentage of steel slag with respect to the coarse aggregate in 0 % - 15% - 25% - 50% - 75%. The results obtained, in terms of quality of the aggregates, complied with the standards of quality. It was concluded that the modified asphalt mixture with 15% steel slag is the best combination, in the same way this percentage complies for light-medium traffic, the remaining combinations (25% - 50% - 75%) only comply for light traffic. It was possible to increase the stability and flow of the incorporated asphalt mixture up to a maximum of 25% for a HMA-2 with respect to the control mixture.

Although steel slag has been used over the past years, the data-based evidence cannot even be found to indicate the development of steel slag-related technologies. To clarify the leading regions, reveal the research trends, and propose future research directions, a bibliometric and visualization analysis was conducted based on the Web of Science (WOS) core databases. China, the USA, and Italy are the top three eminent countries, and the institution of Tsinghua University and Wuhan University of Technology tied for the first place with an H-index of 27. The research focus of steel slag has changed from mechanical properties, such as durability and strength, to functional applications, pretreatment technology, carbon sequestration, and environment-friendly products. Finally, several research directions were proposed for future investigation. This was the first time steel slag was investigated from a bibliometric perspective. The information obtained could provide scholars with the current recycling situation and the following academic steps.

Steel slag has been commonly used in road engineering as cementitious material; however, its application in base course is not widely reported. Four contents of steel slag (0%, 30%, 50%, 75% by volume) were blended into different cement (3%, 4%, 5%, 6% by weight)-treated aggregates. Mechanical properties, volume stability, economic benefits and environmental influences of steel slag mixtures were investigated for the feasibility of applying steel slag in semi-rigid base course. Abrasion, crushing and elongated particle content were compared against limestone aggregate, showing that steel slag has the potential of replacing natural aggregate in concrete. Steel slag is beneficial for reinforcement of the strength and stiffness. The mixture has the highest strength and stiffness when bended with 50% steel slag at 4% cement content. By treating steel slag with CH3COOH or adding silica fume, volume expansion of steel slag can effectively be controlled. Larger size steel slag (>4.75 mm) and higher cement content are recommended due to heavy metal leaching risk, especially in salty humid areas. Steel slag has sound economic benefits due to the relatively low price. Environmental benefits can also be achieved given that the transport CO2eq emission of steel slag is accounted for. With proper control in production process, steel slag is a very promising alternative material to be utilized in cement-stabilized base course in road engineering.

The effective resource utilization of steel slag from bulk solid waste can achieve good social, environmental and economic benefits. In order to restrain the volume expansion of steel slag and apply it as a building material, in this work, oxalic acid was used for the treatment of steel slag, and the mechanism of oxalic acid restraining the expansion of steel slag was explored. This study recovered the main metal ions in steel slag while restraining its volume expansion. The volume stability of the eroded steel slag and the phase composition, microstructure, roughness and pore size distribution of the steel slag after oxalic acid erosion were investigated. The hydration process of the steel slag was characterized using the pH value, the ion distribution of the leachate was measured, and the leachate was recovered via ultraviolet catalysis and evaporation crystallization. The results showed that a large number of calcium and iron minerals in the steel slag reacted with adipic acid to form calcium oxalate, which precipitated on the surface and opened pores in the steel slag during the process of adipic acid erosion, which improved the compactness of the steel slag’s surface and improved the volume stability of the steel slag. After erosion, the surface roughness, specific surface area and porosity of the steel slag decreased, and the average pore diameter (μm) decreased from 1.717 to 0.208. In addition, the pH value was stable at approximately 7.3 over long-term interaction with water. The leachate was mainly composed of iron, calcium and silicon ions, accounting for 35.43%, 17.17% and 17.05%, respectively, which were recovered by ethanol and ammonia to obtain calcium oxalate, ferrous oxalate, ammonium oxalate and a metal hydroxide. The hydration activity of the steel slag treated with oxalic acid decreased and the volume expansibility of the steel slag was effectively restrained. The expansion rate of the steel slag decreased from 3.59% to 1.69% and the volume stability of the steel slag improved. The leachate recovery efficiency was high and was close to 100%. The utilization of steel slag as a resource was realized and the environmental problems caused by the steel slag were effectively solved.

Phosphated hydrotalcite (P-LDHs) was synthesized from steel slag and modified hydrotalcite (SDS-P-LDHs) was obtained by intercalation of P-LDHs with sodium dodecyl sulfate (SDS). P-LDHs and SDS-P-LDHs were blended with expanded graphite and ethylene vinyl acetate copolymer (EVA),to prepare EVA foam composites, respectively. The surface morphology and structure of P-LDHs and SDS-P-LDHs were characterized by XRD, XRF, FT-IR, SEM and TEM. Combined with limited oxygen index(LOI), UL-94, SEM, TG, tensile strength and elongation at break, the effects of P-LDHs and SDS-P-LDHs on the flame retardancy and mechanical properties of EVA foam composites were discussed. The results show that the addition of P-LDHs and SDS-P-LDHs significantly improves the flame retardant properties of EVA foam composites and can play a good role in charring formation. Compared with P-LDHs, SDS-P-LDHs have better compatibility with EVA matrix. When the addition amount of SDS-P-LDHs is 30%(mass fraction), the LOI reaches 27.5%, UL-94 reaches V-0 level, tensile strength and elongation at break are 2.27 MPa and 251%, respectively. The comprehensive properties of the system are optimal.

Steel slag is being used worldwide for a variety of applications, among which is underwater dyke reinforcement. In the present study the leaching and bioaccumulation of 18 inorganic compounds from basic oxygen furnace (BOF) steel slag were monitored in marine experimental ecosystems (mesocosms) for 12 wk. Triplicate mesocosms were installed at 2 refreshment rates, one reflecting the situation in the Oosterschelde estuary where BOF steel slag was applied and the other at a 35 times lower rate. Vanadium in both water and biota turned out to be the best tracer for the presence of BOF steel slag in the mesocosms. The mesocosm data helped to interpret the results of a 4‐yr field sampling program in the Oosterschelde estuary where no elevated levels of vanadium in water or biota were found near locations where steel slag was applied. Also, no ecological impact could be established in the field, which was in line with the observations in the mesocosms. The present study shows the added value of a tailor‐made mesocosm study for realistic risk assessment and provides support for applying this tool as a basis for designing efficient field monitoring programs. Environ Toxicol Chem 2021;40:2499–2509. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

This work facilitates the application of modern technologies for road construction, by using steel slag instead of natural stone aggregates. This procedure will result in a significant decrease in the cost of works (slag, being an industrial waste, is much cheaper than natural aggregate). In the same time, the use of slag aggregates can result in protection of the environment, by eliminating slag storage spaces and by preserving the natural environment (extraction of natural aggregates may disturb groundwater and intensify erosion etc). Marshall stability, flow index and bulk density were determined for both kinds of aggregates, in order to find if the steel slag can safely replace the natural aggregates. By comparing the experimental results obtained for the two kinds of aggregates, it was confirmed the possibility of successfully using of steel slag as a substitute for natural aggregates in the base layer of a road structure.

Concrete is as a significant building material. Due to the fact that it is possible to incorporate by-products and industry waste into its structure, concrete represents an important sustainable material. Steel slag has a great potential for its reuse in concrete production. Despite that it is subject to volume changes over time, it can be used in concrete as a cement replacement or as a substitute for natural aggregates. The paper is focused at investigation the concretes with steel slag as a substitute of natural gravel aggregate of 4/8 mm and 8/16 mm fractions. In addition, a life cycle assessment within the system boundaries cradle-to-gate was performed. Results showed that some samples with slag have better mechanical parameters than samples with natural aggregate and significantly affect the utilization rate of non-renewable raw materials and reduce the overall negative environmental impacts of concrete up to 7 %.

Fine-grained soils usually have low shear strength and bearing capacity and high swelling potential in the wet state, therefore, they have often to be stabilized by additives. The main objective of this study is to determine the possible effects of ground-granulated blast-furnace slag on the physical and mechanical properties of fine-grained soil. For this purpose, a number of Atterberg, compaction, California bearing ratio (CBR), unconfined compression and freeze-thaw tests were conducted on fine-grained soil. Steel slag (SS) inclusion reduced plasticity index of soil from 44% to 20% when slag content increased from 0% to 55.0%. Moreover, the slag addition improved soil CBR with maximum improvement rate in the sample consists to 55% slag. This increment in CBR was about 140% and 154% for 2.54 mm and 5.08 mm penetration respectively. In addition, slag inclusion raised soil strength with a maximum increment of 132% for clay mixed with 55% slag. Water content and volume changes in freeze-thaw cycles also decreased with increasing percentage of SS, therefore mixtures durability increased.

Cemented paste backfill (CPB) is a sustainable mining method that has been increasingly utilized. Demand for high-performance and low-cost binder material is one of the limitations in CPB utilization. This work aims to examine a new, green, and economical steel-slag-based binder for CPB and to explore valorization techniques of steel slag (SS). Proportioning experiments were performed to obtain the best binder recipes for various steel slag dosages. The hydration heat, hydration products, and pore structure of a high-volumetric steel slag binder (H-SSB) were further inspected. Results show that the H-SSB, which contains 50 wt.% of SS, has a competitive strength performance superior to ordinary Portland cement (OPC) regardless of its 30–50% lower cost than OPC. The 7-day and 28-day strengths of H-SSB CPB are 1.24 and 0.74 MPa, respectively, which meets the meets of most free-standing backfill applications. The H-SSB generates less hydration heat and a larger amount of gel and ettringite hydrates than OPC in its early hydration, which can reduce the thermal expansion risks and strengthen the mechanical properties of CPB. Though the H-SSB CPB has a larger porosity than OPC-CPB at 28-day curing (45% vs. 37%), most pores are small and uniform in diameter (500–2000 nm), which is less harmful to CPB strength development. The H-SSB has secondary hydration effects in the long-term age, which can fill and refine the pore structure. The proposed H-SSB has benefits in reducing backfill costs, minimizing green gas emissions, and extending steel slag valorization techniques that can promote sustainable development of the mining and steel industries.

Electrokinetic (EK) remediation methods can remove heavy metals from the soil, but the removal efficiency is generally low. In this paper, indoor remediation experiments of simulated copper-contaminated clay under four different types of electrolyte conditions (KCl, HAc, AC, and PASP (polyaspartic acid)) are carried out to validate the theory of an electrodynamically coupled steel slag permeability reactive wall (PRB). By comparison with EK remediation, it has been shown that the EK-PRB coupled remediation method can promote the removal of heavy metal copper in the soil, especially in the removal of reducible copper and exchangeable copper. The method can effectively avoid the increase in soil pH value and reduce the accumulation range of heavy metals while reducing the accumulation amount of heavy metals. This method has better energy utilization efficiency, and the unit energy consumption is smaller than the single electric remediation test.

The reuse of steel slag, a large-scale solid waste from steel production, has good social and environmental benefits. The application of a steel slag asphalt mixture is mainly hindered by its volume expansion in water. The expansion of steel slag can be inhibited by oxalic acid. The expansion rate and adhesion of steel slag were investigated, and the immersion stability of steel slag and its asphalt mixture was evaluated by water erosion. By means of XRD, XRF, TG, SEM, etc., the influence mechanism of oxalic acid and water erosion on the properties of steel slag and its asphalt mixture was discussed. The results show that oxalic acid can not only inhibit the expansion of steel slag but also improve its crush resistance, with a reduction in the expansion rate of steel slag by 53%. Oxalic acid is able to leach alkaline metal elements, reducing its adhesion with asphalt. After 10 days of water erosion, the rutting stability and bending crack resistance of the treated steel slag mixture decreased by 37% and 43.2%, respectively. Calcium oxalate is generated on the surface of treated steel slag, which improves the surface compactness, effectively inhibits the expansion of steel slag caused by water erosion, and improves the performance of steel slag and its asphalt mixture. Water erosion can accelerate the hydration and shedding of calcium-containing substances on the surface of steel slag, reduce the adhesion of steel slag, and lead to degradation in the performance of steel slag and its asphalt mixture. Oxalic acid is able to effectively inhibit the expansion of steel slag, and the treated steel slag can be used as recycled aggregate in asphalt mixture, effectively solving the problems of road aggregate deficiency and environmental pollution caused by steel slag.

Ferrocement composites have uniform distribution and high surface area to volume ratio of reinforcement, which identifies them as a good strengthening material for use in structural applications. Because of these properties, they are considered as a substitution for some conventional structural strengthening methods. In this study, ten reinforced concrete (RC) beams of size 1220 mm × 100 mm × 150 mm were strengthened with ferrocement composites using a galvanized square weld, having volume fractions of 1.76% and 2.35%. For this study, ferrocement composites with mortar 1:2, w/c 0.4, and steel slag, with a 30% weight fraction of fine aggregate, are considered. The experimental results showed that the first crack load and the ultimate load are higher for RC beams strengthened with ferrocement having a volume fraction of 2.35% (Vr) and a steel slag replacement of 30%. Theoretical predictions were made based on the elastic moment approach; the ratio between the prediction to experimental moment capacity ranges between 0.99 and 1.04. The outcomes show that ferrocement is an effective strengthening technique for deficient reinforced concrete members

Çalışma kapsamında iki atık malzeme olan Yüksek fırın cürufu (YFC) ve Çelikhane cürufu (ÇC) kullanılarak çimento yerine alternatif bağlayıcı elde edilmeye çalışılmaktadır. Bu amaçla, YFC ve ÇC farklı oranlarda kullanılarak geopolimer harçlar üretilmiştir. Cüruflar, %80 YFC+ %20 ÇC ve %60 YFC+ %40 ÇC olacak şekilde çimento yerine ikame edilerek kullanılmıştır. Cüruflu harçların aktivasyonu için %3, %5, %7.5 ve %9 oranında Na2SiO3 kullanılmıştır. Cüruflu geopolimer harçların 28 günlük basınç dayanımı sonuçları; %80 YFC+ %20 ÇC için sırasıyla; 40.14, 47.28, 59.87 ve 76.25 MPa olarak belirlenmiştir. %60 YFC+%40 ÇC içeren geopolimer harçların basınç dayanımları; 25.57, 44.92, 54.23 ve 66.65 MPa olarak belirlenmiştir. Dayanım sonuçları, geopolimer harçların %7.5 ve %9 Na2SiO3 oranlarında Portland çimentosuna kıyasla daha iyi dayanım verdiğini göstermektedir. Dayanım sonuçlarına bakıldığında, cüruflu geopolimer harçların çimento yerine bağlayıcı bir malzeme olabileceği anlaşılmaktadır.

The bulk of the cement industry’s environmental burden is from the calcareous source. Calcium is mostly available naturally as limestone (CaCO₃), where almost half of the mass is eventually released as CO₂ during clinker manufacture. Iron (Fe) is the fourth most common element in the Earth’s crust surpassed only by oxygen, silicon, and aluminium; therefore, potential raw materials for alternative cements can contain significant amounts of iron. This review paper discusses in detail the most abundantly available Fe-rich natural resources and industrial by-products and residues, establishing symbiotic supply chains from various sectors. The discussion then focusses on the impact of high iron content in clinker and on ferrite (thermo)chemistry, as well as the importance of iron speciation on its involvement in the reactions as supplementary cementitious material or alkali-activated materials, and the technical quality that can be achieved from sustainable Fe-rich cements.

The objective was to evaluate the influence of Baosteel slag short flow (BSSF) steel slag, a byproduct of a Brazilian steel mill, as a fine aggregate on the properties of fresh state and on the compressive strength of mortars. The experimental work was to characterize the BSSF steel slag and to produce simple mortars (only cement) and mixed mortars (cement and lime), replacing the natural sand with the slag aggregate in 20%, 40%, and 60% by volume. The fresh state tests were specific mass, incorporated air, water retention, and squeeze-flow, while in the hardened state, compressive strength at 28 days was investigated. It was verified that mortars with higher slag contents required greater amounts of water to obtain the spread (consistency) on the flow table, which was fixed at 260±5 mm. The mortars with slag presented higher specific mass since the slag had a higher density than natural sand and less water retention in the case of simple mortars. In addition, it was verified that the mortars with BSSF steel slag presented lower values of maximum displacement in the squeeze-flow test, which negatively affected its workability in the fresh state, besides the properties of mortar adherence. In addition, it was verified through the analysis of variance that the substitution of natural sand by BBSF steel slag did not significantly influence the compression strength of mortars.

The change of anthropogenic peatlands to agricultural lands could have negative impacts, namely soil subsidence due to oxidation processes, and reduce the stock of soil organic carbon due to the increase of greenhouse gases (CO2 and CH4) emissions which contribute to global warming. Stability of converted peatlands could be increased through amelioration of soil by applying steel slag. A laboratory experiment was conducted with using factorial complete randomized design with ten combination treatments, including slag application, of peat soil samples collected from paddy fields in South Sumatera. This study determined the effect of steel slag application on reducing greenhouse gas (CO2 and CH4) production from cultivated peatland soils. The first factor of experimental treatment was peaty soil from 5 different locations, and the second factor was the application of steel slag. The highest production potentials of CH4 and CO2 were shown by peaty paddy soils from Kayu Agung and Plaju, respectively, while the lowest fluxes were shown by Indralaya’s peaty paddy soil. Peaty paddy soil from the Indrajaya site produced the lowest CO2 and CH4 compared with other sites. Application of steel slag ameliorant reduced CH4 and CO2 emissions by 19.24% and 18.95%, respectively, on average. Slag ameliorant also reduced acidity of peaty paddy soils.

This study presents a sustainable approach for metal extraction from a range of secondary resources. Organic acids analogue to those commonly produced by heterotrophic microbes are applied via a two-step heterotrophic bioleaching approach. New insights into leaching mechanisms are developed and the potential use of the leaching residues as cementitious component is evaluated. Tested materials include a jarosite sludge from Zn refining, four ferrous metallurgy residue sludges and two dry automotive recycling shredder residues. Screening experiments tested three organic acids (i.e. citric, gluconic, oxalic acid) and their combinations. Four physicochemical factors were varied, i.e. the solid/liquid ratio between 5 and 15%, total organic acid concentration between 20 and 200 mM, leaching times of 2 to 4 h and horizontal stirring reactor mixing rate. The highest extraction capacity was achieved for a Cr/Ni rich sludges from steel treatment with up to 96% Ni and 91% Cr extraction at a 5% S/L and a mixture of 100 mM citric and 100 mM oxalic acid. Further scale-up kinetic studies on this Cr/Ni sludge validated the optimal leaching conditions. Modelling of kinetic leaching data indicated pore diffusion rate as a bottleneck of the overall leaching process. Screening tests of the leached residue indicated potential use as sulfate-rich addition to cement, or as part of low-performance binders for large scale civil works.

Asphalt mixtures are composed of two components, namely aggregate and bitumen, so that many structural weaknesses of an asphalt mixture can be resolved by modifying these components. In the past, various research works have been done to improve these weaknesses using a versatile spectrum of different materials. Among others, recycled materials have attracted more attention thanks to their further environmental benefits. On this basis, in the present work, steel slag and recycled polyethylene were used with different compositions at different percent dosages. In order to evaluate the effects of these two materials, we used resilience modulus test, Marshall Resistance test, dry and wet indirect traction tests, and moisture sensitivity test. Results showed that incorporation of both materials in a mixture provides for a better output than the use of either of them alone. Indeed, the blending of these two materials helps address the weaknesses of either of them.

Circular utilization of reclaimed asphalt pavement (RAP) has received extensive attention for its economic and environmental benefits. The application of recycled asphalt mixtures (RAM) in the upper layer of asphalt pavement faces the issue of inferior anti-slip performance and durability. This study aims to recycle steel slag as virgin aggregates in RAM and quantitatively evaluate the service performance of RAM with steel slag. Steel slag and basalt RAM were firstly fabricated and the five different RAP contents were involved. Then tests of Marshall stability, indirect tensile strength and Cantabro spatter loss were conducted to investigate the moisture susceptibility of RAM. Moreover, their high temperature stability, crack resistance and skid resistance were characterized. Indirect tensile fatigue test combined with Hamburg wheel tracking test were carried out to discuss the durability of RAM. The comprehensive performance of RAM with steel slag were quantitatively assessed based on an improved radar chart evaluation method. The results show that involving steel slag reveals a remarkable enhancement function on water stability, high and low temperature performance, skid resistance and fatigue resistance of RAM. Steel slag RAM with 50% RAP content demonstrates a rutting depth of 7.60 mm and a creep slope of 2.54 × 10−4, indicating its superior durability in high temperature and water environment. Compared with the comprehensive evaluation function of 0.5336 for basalt RAM with 30% RAP dosage, steel slag RAM reaches 0.7801, which represents its preferable road performance.

Blue carbon ecosystems are crucial for carbon sequestration on a global scale. However, it is unclear how we could promote and maximize carbon sequestration. Here, we demonstrate that providing an iron source to seaweed fostered its growth through increased photosynthetic efficiency and transformed the carbon into a biomass. Firstly, we revealed that the mixture of the steel slag and DTPA eluted iron dramatically in seawater. Next, we applied the eluate of the slag-DTPA pellet to the seaweed. The results for the eluate treatment showed a 25.8% increase in the photosynthetic pigment level and a 44.9% increase in the seaweed weight. Furthermore, we confirmed no elution of potential toxic substances from the steel slag and DTPA pellet. Finally, we applied the pellet at a depth of 15 m near seaweeds and observed a 52.0% increase of carbon weight in the pellet treated group, while the non-treated group showed only a 10.3% increase for five months. This study indicated that steel slag-DTPA pellet treatment induced seaweed growth and efficiently transformed its carbon into a seaweed biomass. Thus, steel slag and its chelating agent may contribute to the promotion of sea forestation and a subsequent increase in carbon sequestration known as blue carbon.

This research tests energy optimised furnace (EOF) steel slag as substitution for natural coarse aggregate in concrete. Steel slag’s usefulness as a substitute for natural coarse aggregate in concrete is the primary goal of this research. According to IS:2386-1963, the characterization of EOF steel slag, as coarse, is done by examining the shape and size of a particle, mechanical properties, physical properties, soundness, and alkali-aggregate reactivity. Tests for detection of staining material in steel slag and hardness of inter-facial transition zone in hardened cement paste were also carried out. The chemical analysis of the steel slag reveals the stability of oxides present in the steel slag. Microstructural characterization by SEM (scanning electron microscope) analysis of steel slag aggregate was also employed to support the characterization and XRD analysis, and it was found that the EOF steel slag is crystalline. The digital image processing technique (DIP) is adopted to study the shape indices, circularity, sphericity, shape factor, and roundness of natural and EOF steel slag aggregate. According to the characterization and strength investigation, steel slag aggregate outperforms natural coarse aggregate.

Methods and materials that effectively remove heavy metals, such as lead and copper, from wastewater are urgently needed. In this study, steel slag, a low-cost byproduct of steel manufacturing, was utilized as a substrate material for carbon nanotube (CNT) growth by chemical vapor deposition (CVD) to produce a new kind of efficient and low-cost absorbent without any pretreatment. The synthesis parameters of the developed CNT–steel slag composite (SS@CNTs) were optimized, and its adsorption capacities for Pb(II) and Cu(II) were evaluated. The results showed that the optimal growth time, synthesis temperature and acetylene flow rate were 45 min, 600 °C and 200 sccm (standard cubic centimeter per minute), respectively. The SS@CNTs composite had a high adsorption capacity with a maximum removal amount of 427.26 mg·g−1 for Pb(II) and 132.79 mg·g−1 for Cu(II). The adsorption proceeded rapidly during the first 15 min of adsorption and reached equilibrium at approximately 90 min. The adsorption processes were in accordance with the isotherms of the Langmuir model and the pseudo-second-order model, while the adsorption thermodynamics results indicated that the removal for both metals was an endothermic and spontaneous process. This study showed that compared with other adsorbent materials, the SS@CNTs composite is an efficient and low-cost adsorbent for heavy metals such as lead and copper.

This paper presents a method to make biocement using steel slag and apply it for soil improvement. Steel slag contains calcium which can be converted into calcium chloride or calcium acetate using ammonium chloride or plain vinegar. Calcium chloride or calcium acetate so produced can be used for biocementation via microbially induced carbonate precipitation (MICP). The concentration of calcium ions extracted using plain vinegar is higher than that using ammonium chloride. The cementation effect for sand using calcium acetate is better than or as good as that using calcium chloride in both one-phase and two-phase treatment methods. The crystal types of calcium carbonate in the biocemented sand using calcium acetate are mainly calcite and vaterite. The study in this paper shows that the biocement produced using steel slag has two main advantages: 1) it is more cost-effective and sustainable as steel slag as a waste material is used; 2) it is chloride free and thus can be used in many cases where the conventional cementation method is not applicable such as in the present of reinforced concrete. Ministry of National Development (MND) Submitted/Accepted version The authors would like to acknowledge gratefully the support provided by the Ministry of National Development, Singapore (Grant No. CoT-V1-2020-4).

Steel slag is a by-product obtained through the separation of molten steel from impurities in steel-making furnaces. It can be produced by different types of furnaces (blast, basic oxygen, electric arc, ladle furnaces). The reuse of metallurgical slags in road pavements can pursue aims of recycling and environmental sustainability. Based on the extensive literature, the paper presents a state-of-the-art review concerning the use of slags in asphalt pavements, discussing the main controversial literature findings. Slag manufacturing processes, chemical, morphological, and physical characteristics, affect its contribution to the asphalt mixture, when it partially or fully substitutes natural aggregates. Legislative state-of-the-art environmental issues, weathering, and leaching aspects are also discussed. The main mechanical and durability properties of pavements containing different types of slags are analyzed based on laboratory and field studies. Generally, the higher mechanical properties of steel slag suggest that its inclusion in asphalt mixtures can provide high-performance pavement layers (excellent strength and stiffness, superior rutting and fatigue resistance, low moisture susceptibility). However, several research gaps still exist (e.g., mix design and seasoning procedure, bitumen–aggregate affinity, low-temperature behavior, brittleness); they are discussed to direct possible future study efforts to clarify specific technical aspects, such as, for example, the effect of slag morphology and physical properties on the final mix properties and the development of specific mix design guidelines.

The demand for more sustainable transport infrastructure has led to a broader acceptance of waste materials in pavements. An excellent example of this trend is the incorporation of steel slag aggregates (SSA) in asphalt mixtures. This work evaluates the mechanical performance of asphalt mixtures that include SSA in their composition. Asphalt mixtures were evaluated through laboratory tests for affinity between binder and aggregate, Marshall and volumetric properties, stiffness, resistance to fatigue, permanent deformation, and water sensitivity. Two rates of SSA incorporation—20% and 35%—were considered. In general, results indicated that incorporating SSA has not impaired the behavior of the asphalt mixtures. In some cases, the presence of SSA has improved mechanical performance. It was the case of the resistance to permanent deformation, stability, flow, and water sensitivity. This work confirms the suitability of the SSA application in asphalt mixtures beyond the benefit of promoting industrial waste in pavement engineering.

Every year, the steelmaking industry produces millions of tons of slags resulting in pollution to the environment. Among the waste, secondary metals and scales rich in iron oxides are also thrown away. There is a need to treat the steel waste in a reasonably way to protect the environment and proposing new cheap technologies for producing advanced materials. In this study we report the morphological and structural characterization of waste scales generated during roll milling steel process at JSC “Arcelor Mittal Temirtau”. The raw slag and annealed at 1000 °C were measured by X-ray diffraction (XRD), scanning electron microscopy adapted with energy dispersive X-ray (SEM- EDX), magnetometry and Mössbauer Spectroscopy (MS). Fe and O were detected by EDX as main chemical elements and Si, S, Ca, Mg, C and Al as minimal elemental composition. XDR for the raw sample revealed α-Fe2O3 (hematite) and Fe3O4 (magnetite) as principal and secondary phase, respectively; whereas monophasic α-Fe2O3 is detected for the scales annealed at 1000 °C. Magnetometry measurements show the Verwey transition for the raw sample and the Morin transition for the annealed at 1000 °C; those are fingerprints for the presence of magnetite and hematite, respectively. MS measurements for the raw sample consist of 6 small peaks of absorption and a broad two-lines absorption peak in the central part. The doublets are associated to the hyperfine parameters belonging to wustite. Magnetite is related to the hyperfine parameters for two sextets in octahedral Fe2.5+ and tetrahedral Fe3+sites and a small sextet that resembles the Mössbauer parameters of α-Fe2O3. Only a well crystallized and weakly ferromagnetic sextet confirm the presence of α-Fe2O3 phase for the sample annealed at 1000 °C due to thermal oxidation.

Issues like limitation of natural resources of aggregates, global warming, need for eco-friendly, cost-effective, and high performance and durable asphalt mixture, have made the Reclaimed Asphalt Pavements Warm Mix Asphalt (RAP-WMA) and Steel Slag Warm Mix Asphalt (SS-WMA) interesting substitutions for conventional Hot Mix Asphalt mixtures. Furthermore, presence of moisture initiates and accelerates the deterioration of both of these mixtures. In this way, the response of the RAP-WMA to the moisture damage was compared with the SS-WMA using experimental tests including Indirect Tensile fatigue failure, Resilient Modulus, Indirect Tensile Strength, Semi-circular Bending, and Dynamic Creep tests. The obtained results show that although the RAP-WMA and SS-WMA mixtures contain hydrophilic and moisture sensitive aggregates and aged binder, they had an appropriate performance against the effect of moisture. Also, the SS-WMA mixtures showed better performance against moisture than the RAP-WMA mixtures, and therefore, they can be recommended as a substitution for RAP-WMA in regions where moisture damage is prevailing.

The steel industry produces large amounts of slag coming from different stages during the steelmaking process every year. Currently, there are numerous attempts to recycle it or to use it in some other industry sectors and to preserve the environment. The characteristics of the slag depends on the steelmaking process and it is crucial to have it before any attempt of recycling. In this work, slag sample produced in the ladle furnace from SIDERPERU steel plant were collected and analyzed by using energy dispersion X-ray (EDX), X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), SQUID magnetometer and Mössbauer spectroscopy. The chemical analysis obtained by EDX and XRF indicate that the main elemental composition of the material is Fe, Ca, Si and Cr. XRD identifies that these elements are in the phases: FeO, Fe3O4, α-Fe2O3, Ca2SiO4, and Ca2,32Mn0,68SiO7. Magnetometry measurements suggest the Verwey transition for magnetite and the Morin transition for hematite are screened by the presence of superparamagnetic phases. The Mössbauer spectrum shows two doublets related to Fe2+ and Fe3+ ions with hyperfine parameters belonging to that of non-stoichiometric wustite. Also, the presence of hyperfine fields characteristic of the Fe3O4 and Fe2O3 phase identified at room temperature verifies the magnetometry analysis. The analysis of the sample used in this work reveals details connected with the steel fabrication processes and are helpful for posterior recycling attempts.

The chemical and mineral components of the leaching residues obtained during the leaching of inert mineral product (IMP) and two samples of divalent metal oxide continuous solid solution (RO phase) by acetum at 20 °C were analyzed to reveal the selective leaching characteristics of the chemical and mineral components in steel slag, and clarify the leaching rates and differences of MgO and FeO in the RO phase. The results indicated that the content of total Fe (TFe) in the leaching residue increased, whereas the contents of CaO, SiO2, and MgO decreased during the leaching of the inert mineral product by acetum. Fe3O4 was insoluble in acetum. The leaching rates of the RO phase and metallic Fe were very low, while those of calcium silicate (C2S + C3S) and dicalcium ferrite (C2F) were quite high. MgO and FeO in the RO phase continuously leached over time, and the leaching rate of MgO reached 1.9 times that of FeO. Therefore, during the leaching of the RO phase by acetum, the FeO content increased, whereas the MgO content decreased. In conclusion, acetum leaching can effectively improve the TFe content of the RO phase and the inert mineral product.