Carbon Emission Accounting and Multi-Objective Analysis for Steel Slag Road Paving: A Case Study from Xinjiang

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

Saline soil is a special type of soil characterized by a high content of soluble salts and poor engineering properties. This study proposes the use of steel slag to improve saline soil and investigates the effects of different steel slag contents and curing ages on the mechanical properties of saline soil through unconfined compressive strength (UCS) tests, direct shear tests, and Atterberg limits tests. The results indicate that steel slag powder significantly enhances the mechanical properties of saline soil. UCS, stiffness, and cohesion increase with curing age, while they exhibit an initial increase followed by a decrease as the steel slag content rises. The optimal improvement effect is achieved at a steel slag content of 2.5% and a curing age of 28 days, with respective increases of 103.9%, 303.2%, and 162.4%. Additionally, the internal friction angle increases with steel slag content, with a maximum increment of 7.81°. The Atterberg limits test results show that steel slag powder increases the plastic limit of saline soil, whereas the liquid limit and plasticity index decrease with increasing steel slag content. In summary, steel slag exhibits excellent potential for improving the properties of saline soil.

This study investigates the effects of long-term heavy traffic loading on the performance of steel slag asphalt mixtures (SSAMs), including their high-temperature stability, low-temperature crack resistance, water stability, skid resistance, fatigue resistance, and volumetric stability. AC-13 asphalt mixtures with steel slag contents of 0%, 25%, 50%, 75%, and 100% were prepared and used in rutting tests, splitting tests, immersion stability tests, pendulum tests, and four-point bending fatigue tests. The effects of heavy traffic on the high-temperature deformation resistance and skid resistance of the SSAMs were considered by increasing the tire pressure in the rutting test. The results indicated that the high-temperature stability and fatigue resistance first increased and then decreased with the increase in steel slag content, with optimal contents of 75% and 50%, respectively. The low-temperature crack resistance and skid resistance increased with the increase in steel slag content. The volumetric stability decreased with the increase in steel slag content, but the volume expansion rate was less than 1.5% for all SSAMs. Under heavy traffic conditions, the permanent deformation and skid resistance value of the SSAMs significantly decreased. The permanent deformation was minimized when the steel slag content reached 75%. At the same tire pressure, the skid resistance of the SSAMs increased with a higher steel slag content, while the rate of increase slowed down. At the same steel slag content, the skid resistance decreased as the tire pressure increased, while the rate of decrease became slower.

To reduce the use of aggregates such as limestone and basalt, this paper used steel slag to replace some of the limestone aggregates in the production of SMA-13 asphalt mixes. The optimum content of steel slag in the SMA-13 asphalt mixes was investigated, and the performance of these mixes was evaluated. Five SMA-13 asphalt mixes with varying steel slag content (0%, 25%, 50%, 75%, and 100%) were designed and prepared experimentally. The high-temperature stability, low-temperature crack resistance, water stability, dynamic modulus, shear resistance, and volumetric stability of the mixes were investigated using the wheel tracking, Hamburg wheel tracking, three-point bending, freeze–thaw splitting, dynamic modulus, uniaxial penetration, and asphalt mix expansion tests. The results showed that compared to normal SMA-13 asphalt mixes, the high-temperature stability, water stability, and shear resistance of the SMA-13 asphalt mixes increased and then decreased as the steel slag content increased. All three performance indicators peaked at 75% steel slag content, and the dynamic stability, freeze–thaw splitting ratio, and uniaxial penetration strength increased by 90.48%, 7.39%, and 88.08%, respectively; however, the maximum bending tensile strain, which represents the low-temperature crack resistance of the asphalt mix, decreased by 5.98%. The dynamic modulus of the SMA-13 asphalt mixes increased with increasing steel slag content, but the volume expansion at a 75% steel slag content was 0.446% higher than at a 0% steel slag content. Based on the experimental results, the optimum content of steel slag for SMA-13 asphalt mixes was determined to be 75%.

Friction properties of open graded asphalt friction course (OGAFC) mixtures play an essential role in ensuring traffic safety, especially under wet weather conditions. This study evaluated the friction characteristics of basic oxygen furnace (BOF) and electric-arc furnace (EAF) steel slag aggregate incorporated OGAFC mixes. Nine sets of OGAFC mixes were fabricated using five percentage replacements (0%, 25%, 50%, 75%, and 100%) of the coarse natural aggregate fraction by BOF and EAF steel slags. The effect of modified binder type (polymer and crumb-rubber modified) on the frictional characteristics of OGAFC mixes was also examined. The principal friction test devices used were the British pendulum tester and dynamic friction tester. Multiple friction performance aspects were studied: (1) effect of surface condition (dry, wet, and ponding) on the measured friction coefficient; (2) separate evaluation of adhesion and hysteresis friction components; (3) variation of friction coefficient with varying slip speeds, and (4) friction performance later in the OGAFC service life using artificially polished aggregates, and comparison of the performance with unpolished aggregates. Results revealed that the use of steel slags in OGAFC mixes considerably enhanced the frictional characteristics and that the skid resistance of OGAFC-BOF mixes was better than that of OGAFC-EAF mixes. Frictional resistance of the mixes was found to increase with an increase in steel slag content. OGAFC mixes comprising polished steel slag aggregates also showed promising results with the increment in steel slag content. The findings also indicated that OGAFC-CRMB mixes perform better than OGAFC-PMB mixes.

Utilization of unprocessed steel slag as fine aggregate in normal- and high-strength concrete

Towards the co-benefits of carbon capture, utilization and sequestration: A life cycle assessment study for steel slag disposal

The use of steel slag fines has been fully investigated and developed as it has similar chemical composition and mineralogy to that of Portland cement. Researchers from home and abroad have done lots of research on steel slag, such as its production, processing, properties, mechanical behavior, cementitious property and so on. This paper describes influence of water content on mechanical properties of improved clayey soil using steel slag and a series of tri-axial compression tests are carried out to study the influence of water content to the admixture of clayey soils and steel slag. Through the test data statistics and analysis, the basic rules of the mechanical properties of these mixed soils were gotten, especially, the optimum steel slag and water content. Through tri-axial compression tests, there are several kinds of specimen failure forms in different conditions of steel slag and water content. The stiffness of steel slag is larger than clayey soil, so the specimen with steel slag would break with an oblique angle whereas the clayey soil specimen would be compressed. Drawn from the experiment, while water content increases, cohesion c increases and internal friction angel φ decreases; however, in general, the maximum stress difference firstly increases, and then decreases. Under the same water content, with the curing period and steel slag content increase, cohesion c increases, internal friction angel φ decreases, however, the stress difference increases. By analyzing the specimen failure forms and the relations of stress difference and axial strain, the relations between stress difference max (σ1 − σ3) and steel slag content and relations between the secant modulus E50 and steel slag content are gotten. It is concluded that when the water content is about 18 % and steel slag content is about 30 %, the stress difference and secant modulus E50 is larger than other cases. Therefore, in soft soil foundation treatment, such steel slag and water content could be chosen in order that the soil strength would be improved. So, judging from the results, the foundation settlement will be reduced by mixing appropriate steel slag and water content.

Damage characterization and microscopic mechanism of steel slag-cemented paste backfill under uniaxial compression

To explore the low-temperature performance of steel slag crumb rubber powder modified asphalt mixtures, the mix ratio was firstly designed, the optimal mix ratio of compounded steel slag mixtures was selected through the gray target decision theory, and three kinds of asphalt mixtures were prepared. Then the low-temperature performance of steel slag crumb rubber modified asphalt mixtures was comprehensively analyzed through the low-temperature crack resistance, low-temperature creep performance, and low-temperature relaxation performance tests of asphalt mixtures by considering different test temperatures and loading conditions. Finally, based on the linear viscoelasticity theory, the low-temperature creep and relaxation properties were analyzed, and numerical analysis was applied to realize the mechanical response analysis of the mutual transformation of creep flexibility and relaxation modulus. The results show that the road performance of asphalt mixture modified with steel slag partially replacing asphalt mixture with basalt aggregate and asphalt binder modified by crumb rubber of 5∼20-mm particle size is optimal. The larger the proportion of steel slag in the asphalt mixture, the better the low-temperature cracking resistance, creep deformation capacity, and relaxation performance of the asphalt mixture, but the maximum bending tensile strength (RB) and the maximum bending tensile strain (ϵB) of the all steel slag asphalt mixture show unstable patterns of change at lower temperatures (≤10°C). The analysis of interfacial damage coefficients revealed that the ambient temperature as well as the content of steel slag in the asphalt mixture affects the apparent morphology of the cracked surface of the asphalt mixture. Lower temperature or larger steel slag content will cause cracking to concentrate in the asphalt mastic. Numerical analysis revealed that the best results were obtained by converting the relaxation modulus with direct tensile creep tests.

As an attractive substitute of natural aggregate for asphalt mixture, steel slag raises many concerns on the water resistance of steel slag asphalt mixture in frozen and wet areas, due to the special interaction between steel slag and asphalt. This study aims to investigate the deterioration process of water resistance for asphalt mixture with different steel slag contents in dry–wet and freeze–thaw cycles environments. The Marshall immersion test and indirect tensile test were conducted, and the residual stability and tensile strength ratio (TSR) were measured to characterize the water resistance of the steel slag asphalt mixture. Furthermore, dry–wet and freeze–thaw repeated cycling conditions were designed to simulate the effect of actual environments on the long-term water resistance of asphalt pavement. Finally, the microstructures of the aggregate–asphalt interface area were observed, and the enhancement mechanism of the steel slag replacement in asphalt mixture was revealed. Results show that steel slag asphalt mixture exhibits significant resistance to water damage. With the increase in dry–wet or freeze–thaw repeated cycles, the water resistance of steel slag asphalt mixture rapidly deteriorates first and then tends to be stable, and there is a limit state of water damage. In dry–wet repeated cycles condition, the asphalt mixture with 50% steel slag content has a better water resistance, while the asphalt mixture with 100% steel slag content has a better water resistance under freeze–thaw repeated cycles condition. The interface phase structure of steel slag asphalt mixture is stable and dense, where the asphalt mortar evenly and tightly wraps the steel slag and forms a certain penetration depth. The enhancement mechanism of steel slag with asphalt mainly includes the physical anchoring effect and the chemical adhesion effect.

Use of steel slag as sustainable construction materials: A review of accelerated carbonation treatment

Rubberized geopolymer concrete (RuGPC) emerges as an eco-friendly alternative to conventional concrete, significantly reducing greenhouse gas emissions. This study investigates the use of steel slag (SS) in varying proportions (30 %, 35 %, and 40 %) as a replacement for ground granulated blast furnace slag (GGBS) in geopolymer concrete, with crumb rubber (CR) replacing crusher dust (CD) as fine aggregate due to its increasing demand. The research focuses on understanding the impact of aluminosilicate materials on the mechanical, thermal, and microstructural properties of geopolymer concrete cured at 60°C. Advanced characterization techniques, including Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDX), X-ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR), were employed. SEM and EDX analyses revealed that the microstructural properties of GGBS and SS materials, mainly Na/Si, Si/Al, H₂O/Na₂O, and Na/Al ratios, significantly influence RuGPC performance through gel formation. FTIR analysis indicates a shift in the stretching vibrations of GGBS and SS to lower wavenumbers due to geopolymerization changes. XRD results show the formation of C-S-H gel at around 27–30° 2theta, attributed to increased GGBS and SS content. Despite efforts to incorporate CR into geopolymer matrices, challenges in mitigating strength degradation persist. To address this, a predictive model was developed to understand the key factors affecting RuGPC performance. Six machine learning techniques—M5P (pruned and unpruned), random forest, random tree, linear regression, and support vector machine with various kernels (PUK, RBF, PK, and NPK), and artificial neural network (ANN)—were employed to predict the physical and thermal behavior of RuGPC. The analysis identified ANN-based models as the most effective. Sensitivity analysis highlighted the grade of rubber and the CR replacement percentage by volume of CD as the most influential parameters determining RuGPC compressive strength, density, and thermal conductivity. Moreover, The economic analysis revealed that RuGPC mixtures were 1.2–11.61 % more cost-effective than OPC concrete. These findings underscore the importance of predictive model development in optimizing RuGPC properties for practical applications, offering valuable insights for decision-making processes.

Excessive usage of non-renewable natural resources and massive construction wastes put pressure on the environment. Steel slags, the main waste material from the metal industry, are normally added in asphalt concrete to replace traditional aggregate. In addition, as a typical microwave absorber, steel slag has the potential to transfer microwave energy into heat, thus increasing the limited self-healing ability of asphalt mixture. This paper aims to investigate the microwave absorption potentials of steel slag and the effect of its addition on road performance. The magnetic parameters obtained from a microwave vector network analyzer were used to estimate the potential use of steel slag as microwave absorber to heal cracks. Meanwhile, the initial self-healing temperature was further discussed according to the frequency sweeping results. The obvious porous structure of steel slag observed using scanning electron microscopy (SEM) had important impacts on the road performance of asphalt mixtures. Steel slag presented a worse effect on low-temperature crack resistance and water stability, while high-temperature stability can be remarkably enhanced when the substitution of steel slag was 60% by volume with the particle size of 4.75–9.5 mm. Overall, the sustainability of asphalt mixtures incorporating steel slag can be promoted due to its excellent mechanical and microwave absorption properties.

Enhancing mechanical properties of dredged sludge through carbonation stabilization employing steel slag: An eco-friendly and cost-effective approach