Steel Slag Research Articles

Recycling steel slag as aggregate in developing an ultra-thin friction course with high comprehensive road performance

The demand for skid-resistant and wear-resistant alternative aggregates in the preparation of ultra-thin friction course (UTFC) asphalt mixtures is a key direction for achieving high durability and low-carbon development in pavement maintenance. As a typical industrial waste, steel slag with high alkalinity and strong adhesion can facilitate the mechanical property of asphalt mixtures. However, few researches focused on the impact of steel slag on the comprehensive road performance of UTFC mixtures. Hence, the issue merits systematic exploration. In this study, the chemical components, microstructure and morphological characteristics of three steel slags (GXSS, HBSS and IMSS) obtained from different sources were surveyed. Then the stone matrix asphalt (SMA)-5 and open-grade friction courses (OGFC)-5 mixtures with different steel slags were fabricated. And their comprehensive road performances were quantitatively explored via the improved radar chart. The results indicate that steel slag with approximately 40 % Ca content, about 20 % Fe content, irregular shapes and tiny pores endows its wear resistance and strong adhesion. IMSS demonstrates the largest average angularity and form 2D values of 3850 and 7.28, respectively, representing its significant crowding function and interlocking structure. Incorporating steel slag remarkably reinforces the rutting resistance, skid resistance and anti-interlayer shear performance of UTFC. While the effect of water stability and crack resistance of UTFC depend on the category of steel slag. All three steel slags manifest the improvement function on the comprehensive assessment indexes (CAI) of OGFC-UTFC. IMSS-OGFC reveals the optimal comprehensive road performance, achieving the highest CAI of 0.9909. It is inferred that steel slag is more suitable for OGFC-UTFC than SMA-UTFC due to its relatively high CAI and consistent performance regardless of the steel slag type.

Evaluation of carbon nanotube (CNT) cement-based traffic sensor incorporating steel slag based on Accelerated Pavement Test (APT)

ABSTRACT In this study, a carbon nanotube (CNT) cement composite containing CNT and steel slag was developed and its application in traffic information sensing was studied. The mix ratio of steel slag cement mortar matrix and CNT cement composite was determined by mechanical properties and electrical conductivity tests. Then the CNT cement composite intelligent sensing device was prepared and an Accelerated Pavement Test equipment was used to test its piezoresistive response curve. The test results show that steel slag and CNT enhance mechanical properties and electrical conductivity. The vehicle speed and wheelbase were calculated based on the piezoresistive response results, and the calculation errors of the wheel speed (0.375 and 0.844 km/h) were less than 10% and 20%, respectively. The wheelbase estimate has a maximum error of approximately 12% and 15% for wheel speeds of 0.375 and 0.844 km/h, respectively. Therefore, the CNT cement composite containing steel slag developed in this study has the potential to serve as a traffic sensor.

Replacement of conventional aggregates and fillers with steel slag and palm kernel shell ash in dense-graded asphalt mixtures

Large quantities of steel slag and palm kernel shell ash (PKSA) – waste products from steel production and palm oil milling, respectively – are generated annually in several countries, and their disposal is challenging. Meanwhile, the over-reliance on conventional rock aggregates for asphalt mixture production poses increasing sustainability challenges. This study investigated the potential of entirely replacing granite aggregates with steel slag and PKSA in a dense-graded asphalt mixture. Two sets of asphalt mixtures were prepared; the control mixture contained crushed granite aggregate and hydrated lime, while the other set incorporated steel slag as coarse aggregate and PKSA as fine aggregate and filler. Both mixture types utilized AC-30 viscosity-graded asphalt binder. The properties of the waste materials met the quality standards required for aggregates in asphalt mixture production. Both mixture types were designed according to the Marshall design procedure and were evaluated for durability (Cantabro abrasion loss), fatigue cracking Resistance, rutting Resistance, and moisture damage susceptibility. The Cantabro abrasion loss test indicated that the waste-based mixture was 3% less durable than the control. However, the cracking Resistance of the waste-based mixture was approximately twice that of the control. Even though the rapid rutting test indicated that the control mixture was slightly superior in rutting Resistance, the Marshall quotient suggested otherwise. Both mixture types exhibited similar moisture damage resistance. Overall, the steel slag and PKSA samples have shown high potential to replace virgin granite aggregates and lime in asphalt mixtures fully and are, thus, recommended for field performance evaluation and possible adoption.

Evaluation of geotechnical, mineralogical and environmental properties of clayey soil stabilized with different industrial by-products: A comparative study

The utilisation of soil stabilization techniques employing binders like lime or cement enables the use of soils that are classified as disposable, thereby reducing the need for landfills and the consumption of natural resources. However, the production of lime and cement results in significant CO2 emissions. Therefore, the application of industrial by-products (IBP) for stabilizing expansive soils presents an opportunity to minimise the use of traditional binders. This study investigates the geotechnical, mechanical, mineralogical, and environmental properties of four IBP (biomass bottom ash, biomass fly ash, steel slag, and mixed recycled aggregate) combined with a silica-based nanomaterial for road layer applications. The technical feasibility of the use of IBP was demonstrated, especially in combination with nanomaterials, allowing a 66 % reduction in the percentage of added lime, obtaining significant improvements with minimal plasticity and swelling index and bearing capacity CBR values higher than 25 %, applying BBA, BFA and SS. An environmental assessment of leachate analysis was performance, showing an immobilization of heavy metals that makes the application of IBP feasible. In addition, a life cycle analysis study showed the environmental benefits of applying IBP, such as a 50 % reduction in CO2 emissions due to the reduction of lime, resulting from the use of these materials, thus promoting more sustainable economic models.

EFFECT OF ALTERNATIVE RAW MATERIALS OVER CLINCKER QUALITY AND CO2 EMISSIONS

In the cement industry, the actual challenges are the preservation of the raw materials and energy resources, as well as reduction of pollutant emissions. In this context, the cement producers demand studies to reduce of the production costs and atmospheric emissions. One way to achieve these objectives, is to use alternative fuels or by-product raw materials. Any reduction in the required energy has a beneficial influence both on the viability of the cement plant and on the environment. One of the approaches aimed at reducing thermal energy consumption is the partial substitution of traditional raw materials (limestone, clay, gypsum) with other alternative materials, with a melting effect, among which stand out byproducts of the steel industry such as furnace and steel slag. Another way for preservation of energy resources is using alternative fuels instead of traditional fuels like coal, petroleum coke or gas. The clinkering process and clinker quality can be influenced by any additions, in this study was determined these influences.

Carbothermal reduction of flue gas desulfurization ash through the utilization of waste heat from steel slag: Investigating performance and mechanism

Flue gas desulfurization ash is a significant solid waste generated by the steel industry, leading to environmental pollution. In response to this challenge, this study proposes a novel method for preparing CaS from desulfurized ash through carbothermal reduction using steel slag waste heat. Thermodynamic analysis using FactSage and non-isothermal thermogravimetric testing were conducted to confirm the feasibility of carbothermal reduction. The experiment successfully prepared CaS, with a molar ratio of C to CaSO3 of 1.5 or higher leading to complete reduction. The presence of reducing agent C replaced the decomposition reaction of CaSO3 with reduction, occurring at a temperature 60 K lower. Large scale thermogravimetric analysis experiments demonstrated that as the mass percentage of pulverized coal increased, the reduction reaction of CaSO3 shifted to a lower temperature zone, expanding the temperature range and achieving the theoretical value. Reduction rates of CaSO3 were 43.12 %, 76.9 %, and 99.3 % with ratios of CaSO3 to reducing agent C of 1:0.75, 1:1.5, and 1:3, respectively. Kinetic study results showed that the activation energy of CaSO3 reduction ranged from 90.669 kJ/mol to 136.059 kJ/mol within the conversion rate range of 0.2 to 0.9. When CaSO3 and carbon powder are mixed and subsequently added, the thermochemical decomposition reaction of CaSO3 is inhibited. This inhibition leads to the formation of stable CaS through the reduction of desulfurization ash by carbon.

Formulation and characterization of one-part Ca-based alkali-activated slag-steel slag materials

This study aims to develop one-part Ca-based alkali-activated materials (OCAM) using steel slag (SS) and slag powder (SP) with a Ca-based activator. The effects of SS replacement rate on the flowability, setting time, and mechanical properties of paste were systematically investigated. Furthermore, methods such as Mercury intrusion porosimetry (MIP), heat of hydration, X-ray diffraction (XRD), and scanning electron microscope (SEM) were used to compare the effects of calcium oxide (CO) and calcium hydroxide (CH) on the microstructure of the OCAM. The results indicate that the addition of SS enhances mortar flowability and setting time, with optimal mechanical properties when the SS replacement rate is 20 %. However, strength gradually decreases as the replacement rate increases beyond this point. In addition, the incorporation of CO further enhances the mechanical properties of mortar. MIP test results show that the use of CO reduces the internal porosity and refines the micropore structure, although it also increases drying shrinkage. The hydration heat test results reveal that the use of CO increased the total heat release of the sample in the initial 72 h and accelerated the early hydration reaction. Moreover, XRD and SEM results indicate that CO improves carbonation resistance.

Bond between alkali-activated steel slag/fly ash lightweight mortar and concrete substrates: Strength and microscopic interactions

The fire-retardant lightweight mortar spalling from the tunnel lining substrates can threaten the safety of vehicles. The use of steel slag (SS) in alkali-activated cement can reduce the carbon emission and cost of lightweight mortar. The effects of SS on the bond strength and the microstructure of the interface between alkali-activated SS/fly ash (FA) lightweight mortar (ASFm) and concrete substrates was studied. The SS contents, namely, the mass ratio of SS to the summation of FA and SS, were 0 %, 20 %, 40 %, 60 %, and 80 %. The properties of ASFm, including compressive strength, fire resistance and bond strength, were studied. Results demonstrated that the bond strength of ASFm increases and then decreases with the increase in SS content. The highest bond strength of 0.65 MPa was obtained at 40 % SS content. Bond strength was determined by the pore structure and micromechanical properties of the matrix. When the SS content was increased from 0 % to 40 %, the content of C-A-S-H gel and C-N-A-S-H gel contents increased, and the porosity was reduced; hence, the bond strength of ASFm became larger. When the SS content increased from 40 % to 80 %, SS acted as an inhibitor, which reduced the micromechanical properties and increased the porosity of ASFm; therefore, the bond strength of ASFm decreased. This achievement provides an alternative way for the application of SS in tunnels.

Study on Fatigue Performance and Rutting Prediction Model of Steel Slag Asphalt Mixture

Steel slag, a significant industrial waste, poses environmental and land issues due to its accumulation. This research explores using steel slag to replace natural aggregates in steel slag asphalt mixture (SSAM) at varying levels by weight: 25%, 50%, 75%, and 100%. The research evaluated the pavement and fatigue performance of SSAM, noting that dynamic stability (DS) peaked at a 75% slag content. Although low-temperature flexibility decreased, it remained within acceptable limits. The mixture met or exceeded Chinese specifications for resistance to water and traffic stress. Fatigue life varied with slag content, decreasing at high levels due to increased stiffness and stress. A rutting prediction model for SSAM was developed, utilizing a back propagation neural network for accurate rut depth forecasts, demonstrating the model's precision with a fit of 0.99744. This study suggests optimized slag content enhances SSAM performance, offering a sustainable approach to managing steel slag.

The Impact of Fly Ash on the Properties of Cementitious Materials Based on Slag-Steel Slag-Gypsum Solid Waste.

This paper presents a novel low-carbon binder formulated from fly ash (FA), ground granulated blast furnace slag, steel slag, and desulfurization gypsum as a quaternary solid waste-based material. It specifically examines the influence of FA content on the mechanical properties and hydration reactions of the quaternary solid waste-based binder. The mortar test results indicate that the optimal FA content is 10%, which yields a 28-day compressive strength 11.28% higher than that of the control group without FA. The spherical particles of fly ash reduce the overall water demand and provide a "lubricating" effect to the paste due to their continuous gradation, improving the fluidity of the slag-steel slag-gypsum cementitious materials. The micro test results indicate that fly ash has minimal effect on the early hydration products and process of the solid waste-based cementitious materials, but after 7 days, it continuously dissolves silicon-oxygen tetrahedrons or aluminum-oxygen tetrahedrons, consuming Ca2+ and OH- in the system. After 28 days, the amount of ettringite and C-(A)-S-H gel generated increases significantly. The pozzolanic activity of fly ash is mainly stimulated by the Ca(OH)2 from steel slag in the later hydration stage. Additionally, spherical fly ash particles can fill the voids in the hardened paste, reducing the formation of cracks and weak zones, and thereby contributing to a denser overall structure of the hydrated binder. The findings of this paper provide data support for the development of low-carbon cement-free binders using fly ash in conjunction with metallurgical slags, thereby contributing to the low-carbon advancement of the construction materials industry.

Effect of CaO–Al2O3–SiO2–MgO(–CaF2) refining slag system on inclusions in silicon–manganese deoxidized spring steel

In order to make the refined slag match various grades of spring steel, high-temperature equilibrium experiments were conducted in the laboratory to study the effect of CaO–Al2O3–SiO2–MgO refining slag with varying basicity, Al2O3 content, and CaF2 additives on inclusions containing Al (Al2O3) in silicon–manganese-deoxidised steel. The results show that the control effect of low basicity refining slag on inclusions is better than that of high basicity slag. The soluble aluminium increases with the increase of the basicity of steel slag and the Al2O3 content in inclusions is positively correlated with the Al2O3 content in slag. When the relative adsorption capacity of the refined slag is 6 × 10−3, the area density of Al-containing inclusions in steel is at a low level. Low basicity slag with low Al2O3 is good, and it is more suitable for producing high-end spring steel. To produce middle- and low-end spring steel, the refining slag system with a basicity of about 2–2.5, Al2O3, MgO, and CaF2 content is about 10% can be used. Among them, a small amount of CaF2 improves the liquidity of steel liquid, improves its relative adsorption capacity to Al-containing inclusions, and can control the production of Al-containing inclusions in the steel.

Eco-Friendly 3D-Printed Concrete Using Steel Slag Aggregate: Buildability, Printability and Mechanical Properties

Utilizing steel slag aggregate (SA) as a substitute for river sand in 3D concrete printing (3DCP) has emerged as a new technique as natural resources become increasingly scarce. This study investigates the feasibility of using steel slag (SS) as fine aggregate for 3DCP. Ninety mixtures with varying steel slag aggregate-to-cement ratios (SA/C), water-to-cement ratios (W/C), and silica fume (SF) contents were designed to study the workability and compressive strength of the 3D-printed concrete. Additionally, the actual components were printed to evaluate the printability of these mixtures. The experimental results indicate that it is feasible to fully employ SA in concrete for 3D printing. Mixtures with slump values ranging from 40 to 80 mm and slump flow values varying from 190 to 210 mm are recommended for 3D printing. The optimal mix is determined to have SA/C and W/C ratios of 1.0 and 0.51, respectively, and an SF content of 10% by cement weight. A statistical approach was utilized to construct the prediction models for slump and slump flow. Moreover, to predict the plastic failure of the 3D-printed concrete structure, the modified prediction model with an SA roughness coefficient of 4 was found to fit well with the experimental data. This research provides new insights into using eco-friendly materials for 3D concrete printing.

Hydration behavior and thermodynamic modelling of ferroaluminate cement blended with steel slag

This study investigates the effect of steel slag (SS) content on hydration of ferroaluminate cement (FAC). The physical and mechanical properties, hydration properties and microstructure of the cement paste mixtures were also evaluated. The results reveal that the setting time initially shortens and then prolongs while the fluidity, electrical resistivity at 24 h, and chemical shrinkage at 3 days decrease with the increase of SS from 0 % to 30 %. In addition, the analysis of hydration products shows that the incorporation of SS promotes the growth of strätlingite in the SS-FAC paste, which is responsible for strength recovery of FAC at a late period. The compressive strength of the paste with 20 % SS at 90 days exceeded that of the control group. The addition of a small amount (≤20 %) of SS can improve the pore distribution of the SS-FAC paste and have a certain improvement effect on its microstructure in the late periods of hydration. Thermodynamic modelling shows that the growth of AFt and strätlingite (C2ASH8) in the SS-FAC paste is promoted, which is consistent with the experimental results.

Microwave self-healing characteristics of the internal voids in steel slag asphalt mixture subjected to salt-freeze-thaw cycles

Microwave heating technology can be used to repair freeze-thaw (F-T) cycle damage and cracks caused by the use of snow melting salts and de-icers in winter. This study utilized three different gradations of asphalt mixtures: AC-13, SMA-13, and OGFC-13, and enhanced their microwave absorption performance with steel slag (SS). The heating uniformity was evaluated through surface and internal temperature tests. Additionally, the mechanisms of damage and healing of the asphalt mixtures under salt freeze-thaw (S-F-T) damage conditions were explored using S-F-T cycles test and X-ray computed tomography scans (CT). The results showed that OGFC-13 exhibits a significantly higher rate of temperature increase compared to the other two types due to its stronger wave absorption capacity. The thermal hysteresis caused by steel slag leads to uneven spatial temperature distribution. The study recommends an optimal microwave heating time of 40 s for SS asphalt mixtures, which has minimal impact on the mixture structure, by defining an evaluation method for the uniformity index and local overheat ratio. After undergoing S-F-T cycles, the porosity of all three asphalt mixtures increased, particularly at the top and bottom of the specimens. Among them, OGFC-13 exhibited the poorest durability under S-F-T conditions, with the S-F-T cycles having a significant impact on medium-sized voids (0.15–0.6 mm). After microwave heating, AC-13 and SMA-13 showed good repair effects, with porosity levels returning to their initial states. For large voids (>2.36 mm) in OGFC, microwave heating may not effectively reduce the number of voids. Additionally, the healing rate of mixture specimens at certain mid-height ranges is higher due to elevated surface temperatures in these areas, making it especially effective in repairing F-T damage. This study shows that microwave heating of SS asphalt mixtures can improve the durability of pavement in cold regions. However, implementation challenges include the need for specialized equipment and potential uneven heating. Future research should explore optimizing microwave heating techniques to minimize local overheating and investigate the long-term performance of microwave-repaired asphalt pavements under various environmental conditions.

Synergic valorization of nickel-chrome plating sludge via alkali activation of steel slag and fly ash: performance analysis

Synergic valorization of nickel-chrome plating sludge via alkali activation of steel slag and fly ash: performance analysis

Enhancing effect of β-cyclodextrin on carbonation properties of steel slag

In order to improve the carbonation properties of steel slag, the carbonation reaction process of steel slag and the formation of carbonation products were regulated by the interaction between multiple hydroxyl groups within β-cyclodextrin (β-CD) molecule and calcium ions leached from steel slag. Through a meticulous experimental design, varying contents of β-CD, from 0.0 % to 5.0 %, were mixed with steel slag to investigate their impact on carbonation kinetics, mechanical strength, and microstructural evolution. The results indicate that β-CD significantly accelerates the carbonation process of steel slag, with a particular boost to the carbonation of β-dicalcium silicate (β-C2S), a key mineral contributing to the carbonation activity. At an optimal β-CD concentration of 2.5 %, the compressive strength of the treated slag reached a peak of 138.5 MPa, marking a 13.4 % improvement over the control sample. Similarly, the CO2 uptake was optimized at 17.9 %, increasing by 21.8 %. Mechanism analysis reveals that β-CD not only facilitates carbonation but also refines the resulting carbonation products, leading to a denser microstructure and enhanced mechanical properties. However, at a β-CD content of 5.0 %, the carbonation process was hindered by excessive viscosity. These pivotal findings propose an innovative strategy to augment the efficiency of carbonation and the inherent material properties of steel slag, thereby fostering a more sustainable approach to the utilization of industrial byproducts.

Influence of Steel Slag on Properties of Cement-Based Materials: A Review

Influence of Steel Slag on Properties of Cement-Based Materials: A Review

The Utilization of Carbonated Steel Slag as a Supplementary Cementitious Material in Cement.

Carbon emission reduction and steel slag (SS) treatment are challenges in the steel industry. The accelerated carbonation of SS and carbonated steel slag (CSS) as a supplementary cementitious material (SCM) in cement can achieve both large-scale utilization of SS and CO2 emission reduction, which is conducive to low-carbon sustainable development. This paper presents the utilization status of CSS. The accelerated carbonation route and its effects on the properties of CSS are described. The carbonation reaction of SS leads to a decrease in the average density, an increase in the specific surface area, a refinement of the pore structure, and the precipitation of different forms of calcium carbonate on the CSS surface. Carbonation can increase the specific surface area of CSS by about 24-80%. The literature review revealed that the CO2 uptake of CSS is 2-27 g/100 g SS. The effects of using CSS as an SCM in cement on the mechanical properties, workability, volume stability, durability, environmental performance, hydration kinetics, and microstructure of the materials are also analyzed and evaluated. Under certain conditions, CSS has a positive effect on cement hydration, which can improve the mechanical properties, workability, bulk stability, and sulfate resistance of SS cement mortar. Meanwhile, SS carbonation inhibits the leaching of heavy metal ions from the solid matrix. The application of CSS mainly focuses on material strength, with less attention being given to durability and environmental performance. The challenges and prospects for the large-scale utilization of CSS in the cement and concrete industry are described.

Green recycling of used motor oil and steel slag aggregate in concrete

Green recycling of used motor oil and steel slag aggregate in concrete

Synergistic hydration mechanism of steel slag-metakaolin based on ionic dissolution properties combined with industrial CT analysis

Replacing cement with solid waste materials is a key approach to preserving natural resources and mitigating carbon dioxide emissions. In this research, we explored elemental complementation as an eco-friendly and low-carbon approach to develop composite cementitious materials (CCMs) by partially substituting cement with steel slag (SS) and metakaolin (MK), thereby overcoming the low reactivity of SS and facilitating its broader application. We scrutinized the synergistic effects of SS-MK CCMs on parameters such as solubility, water demand, setting time, compressive strength, the formation of hydration products, and microstructure. Employing a suite of analytical techniques, including Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), measurement of hydration heat, and X-ray computed tomography. The findings revealed that the alkaline environment produced by SS-cement powder promoted the breakdown of Si-O and Al-O bonds within MK, facilitating both the early hydration process and the development of strength.MK compensates for the lack of strength caused by the slow hydration of SS in the early stage, while the SS accelerated a pozzolanic reaction of MK, leading to a 28d compressive strength of 54.77 MPa for the composite, while the 28d strength of SS20 was 39.74 MPa; MK effectively utilized portlandite, enhancing the hydration of SS and increasing the production of calcium silicate hydrate, which optimized the pore structure and improved sphericity. Furthermore, the SS-MK CCMs addressed the issues of f-CaO excess and prolonged setting times in the SS-cement system, while also ameliorating the high calcium demand and reduced fluidity in the MK-cement system. Additionally, its lower cumulative heat release from hydration enhances the material’s volumetric stability. This study presents a strategy for the large-scale application of SS and contributes to the value-added, eco-friendly use of industrial solid wastes.