Search Results (72)

Predicting pavement performance is essential for highway planning and construction, considering traffic, climate, material quality, and maintenance. This study’s main objective is to evaluate Baosteel’s Slag Short Flow (BSSF) steel slag as a sustainable aggregate in pavement engineering by means of durability. The research integrates pavement performance prediction using BSSF and assesses its impact on fatigue resistance and percentage of cracked area (%CA). Using the Brazilian mechanistic-empirical design method (MeDiNa), eight scenarios were analyzed with soil–slag mixtures (0%, 25%, 50%, and 75% slag) in base and subbase layers under two traffic levels over 10 years. An asphalt mixture with 15% steel slag aggregate (SSA) was used in the surface layer and compared to a reference mixture. Higher SSA percentages were applied to the base layer, while lower percentages were used in subbase layers, facilitating field implementation. The resilient modulus (MR) and permanent deformation (PD) were design inputs. The results show that 15% SSA does not affect rutting damage, with %CA values below Brazilian limits for traffic of 1 × 10⁶. The simulations confirm BSSF as an effective and sustainable alternative for highway pavement construction, demonstrating its potential to improve durability and environmental impact while maintaining performance standards. Full article

Nowadays, recycling in pavement engineering is not a novelty. Utilization of recycled aggregates and other waste materials for the asphalt layers appeared as a well-established approach during the last decades, at least at a research level, in favor of preservation of natural resources, economical balance in road construction and reconstruction, and overall pavement sustainability. The focus on the asphalt layers does make sense based on the fact that these layers are to be more frequently replaced in the framework of periodical pavement maintenance or rehabilitation. Taking as a fact that mainly laboratory-scale studies and limited field trials have already proven the performance-based viability of using alternative materials in the asphalt layers, including waste plastic, waste glass, steel slag, waste tires in the form of rubber, reclaimed asphalt pavement (RAP), etc., this study tries to identify additional critical aspects and reasons why recycled materials are not consistently selected and uniformly applied during construction and reconstruction activities in real practice. A comprehensive discussion for interdisciplinary issues is provided with respect to (i) the challenge of comparing the performance of asphalt mixtures containing recycling materials with a reference condition status, related to mechanical testing, (ii) the aspect of recycled material availability versus peculiar conditions applied to some countries, related to socioeconomical issues, (iii) the unawareness of the actual lifecycle assessment of pavement structures with recycled mixtures, related to environmental assessment, and (iv) some legislative and health issues that could make pavement engineers reluctant to extensively use non-conventional materials. After a multi-parametric discussion, some useful remarks for fostering further research are given together with the ambition to bridge the gap between research and practice toward a greener future in pavement engineering. Full article

Stone mastic asphalt (SMA) is the most widely adopted asphalt mixture on highway pavement in China. However, the cost of SMA is rising continually due to the increasing shortage of high-quality basalt aggregate. On the other hand, China’s steel slag and reclaimed asphalt pavement (RAP) stock is abundant, and steel slag has excellent strength and wear-resistant performance, which can fully or partially replace part of the basalt aggregate. The content of asphalt may be increased due to the porosity of the steel slag. If fine RAP rich in asphalt is also used for SMA, it can partially fill the voids of steel slag and reduce the amount of new asphalt and fine aggregate. For this objective, SMA 13 was designed with two particle sizes of coarse steel slag aggregate (5–10 mm, 10–15 mm) and one fine RAP (0–5 mm), named SR-SMA. The fundamental pavement performance of SR-SMA was evaluated through a wheel-tracking test, low-temperature beam bending test, freeze–thaw indirect tensile test, and four-point bending fatigue test. For comparison, the mix design and performance tests of two SMAs involving coarse steel slag and fine basalt aggregate (named SB-SMA), and coarse and fine basalt aggregates (named B-SMA), respectively, were conducted. The results indicated that SR-SMA (dynamic stability of 4865 passes/mm) shows the best rutting resistance, followed by SB-SMA (dynamic stability of 4312 passes/mm), and B-SMA (dynamic stability of 4135 passes/mm) comes in last. Additionally, the dynamic stability values of three SMAs have significant differences. SR-SMA has better low-temperature cracking resistance with a failure strain of 3150 με, between SB-SMA and B-SMA (failure strain values are 4436, 2608 με). Compared to B-SMA and SB-SMA, the moisture stability of SR-SMA is relatively poor but meets Chinese specification. While the fatigue resistance of SR-SMA is the worst among three SMAs, their differences are insignificant. Furthermore, SR-SMA reduces material cost by approximately 35% per ton compared to conventional B-SMA. Overall, SR-SMA is cost-effective and can be used as an alternative material to traditional B-SMA. Full article

Asphalt pavements face escalating challenges from traffic loading, climate change, and material degradation, necessitating innovative maintenance solutions. Thermally induced self-healing technologies, leveraging the viscoelastic properties of asphalt binders, can autonomously repair microcracks through targeted thermal activation. This review explored thermally induced self-healing in asphalt mixtures, with a focus on leveraging steel slag as a functional aggregate to enhance sustainability and durability. Two thermal-activation methods, electromagnetic induction and microwave heating, were critically analyzed, highlighting their distinct advantages in heating efficiency, depth, and uniformity. Steel slag offers dual benefits: improving mechanical interlock and skid resistance in mixtures while facilitating efficient heat generation via electromagnetic induction or microwave heating. However, challenges such as hydration-induced expansion, heterogeneous slag composition, and energy-intensive heating processes impede widespread adoption. Pretreatment methods, including natural aging, carbonation, and surface modifications, are essential to mitigate volumetric instability and optimize slag performance. Key factors influencing healing efficacy, including binder properties, operational parameters (e.g., microwave power, frequency), and environmental trade-offs, were systematically evaluated. Future research directions emphasized standardized pretreatment protocols, hybrid heating technologies for uniform temperature distribution, and smart-infrastructure integration for predictive maintenance. Full article

To investigate the dynamic mechanical properties of warm-mix steel slag-crumb rubber modified asphalt mixtures across wide- and narrow-frequency domains and evaluate the applicability of warm-mix technology, four distinct mixtures were prepared. The dynamic modulus characteristics under measured temperatures and frequencies were initially analyzed through complex modulus testing to elucidate narrow-frequency-domain mechanical behavior. Subsequently, leveraging the linear viscoelastic (LVE) theory and time–temperature superposition principle (TTSP), both the 2 Springs, 2 Parabolic Elements and 1 Dashpot (2S2P1D) mechanical element model and Modified Havriliak–Negami (MHN) mathematical model were established based on experimental data to characterize wide-frequency-domain dynamic responses. The results demonstrate substantial consistency in mechanical interpretation between narrow- and wide-frequency domain datasets, with enhanced information resolution achieved in wide-frequency analysis. Both models demonstrate comparable accuracy in characterizing the thermomechanical behavior of warm-mix steel slag-crumb rubber modified asphalt mixture across extended frequency and temperature ranges, while showing negligible performance discrepancies between the 2S2P1D and MHN formulations. Furthermore, both Cole–Cole and Black diagrams convincingly demonstrate the reliability of model predictions. This systematic investigation confirms the technical viability of warm-mix steel slag-crumb rubber modified asphalt mixture while establishing a dual-validated modeling framework for comprehensive performance prediction. Full article

In order to explore the influence of steel slag on the road performance of asphalt mastic and its mixtures, steel slag powder (SSP) and steel slag aggregate (SSA) were used to replace limestone mineral powder filler (MF) and natural limestone aggregate (LA) respectively to prepare asphalt mastic and mixture. A series of standardized tests including penetration, softening point, ductility, viscosity, pull-off strength, dynamic shear rheometer (DSR), and bending beam rheometer (BBR) were carried out to evaluate the performance of asphalt mastics with SSP. Meanwhile, high- and low-temperature performance, moisture stability, volumetric stability, and fatigue resistance were evaluated by wheel tracking, uniaxial penetration strength, Hamburg, three-point bending, freeze–thaw splitting, immersed Marshall stability, water immersion expansion, and two-point bending trapezoidal beam fatigue tests. The results show that compared to the asphalt mastic with MF, enhanced high-temperature deformation resistance and reduced low-temperature cracking resistance of asphalt mastic with SSP were observed, as well as superior aging resistance. The improvements in high-temperature stability, moisture resistance, and fatigue performance were confirmed for asphalt mixtures with SSP/SSA. Additionally, compromised volumetric stability and low-temperature crack resistance were found when SSP/SSA was used in mixtures. Although asphalt mixtures with SSA exhibited 257.79%–424.60% higher expansion rate after 21-day immersion than those with LA, the 3-day immersion expansion rates complied with specification limits (<1.5% per JTG F40-2004). Critical volume expansion control measures should be adopted for full-component applications of steel slag powder/aggregates due to the hydration potential of free lime (f-CaO) and magnesium oxide (MgO) in steel slag under moisture exposure. Full article

This study evaluated the environmental sustainability of partially replacing natural aggregates with electric arc furnace (EAF) slag in concrete and porous asphalt mixtures. Both the Equilibrium Leaching Test (EN 12457-4) and the Dynamic Surface Leaching Test (DSLT, CEN/TS 16637-2) were applied to analyse the leaching behaviour of the asphalt mixtures. The results showed that the incorporation of EAF slag led to the release of chromium (Cr), molybdenum (Mo), and vanadium (V), while the type of bitumen affected the dissolved organic carbon (DOC) release. However, when compared to EAF slag leaching, asphalt mixtures exhibited significantly reduced leaching, particularly Cr (by 70%) and V (by 60%). These results indicate that metal leaching follows a diffusion-controlled release mechanism, showing higher concentrations for the porous asphalt compared to the asphalt concrete. The cumulative leaching values at 64 days reached 2.54 mg·m⁻² for Cr, 3.29 mg·m⁻² for Mo, and 28.67 mg·m⁻² for V, far from the limits set by the Dutch Soil Quality Decree (SQD) of 120, 144, and 320 mg·m⁻², respectively. Therefore, this study demonstrated that EAF slag is a viable alternative for sustainable road construction, reducing natural resource consumption and promoting the circular economy. Full article

Steel slag is a common solid waste, but it has good microwave absorbing ability. The poor microwave sensitivity of asphalt mixture limits the development of microwave maintenance for asphalt pavement. Therefore, it is significant to apply steel slag to asphalt pavement. This study analyzes the difference in the microwave sensitivity and performance between the asphalt mastics with blast furnace slag powder (BFSP), converter slag powder (CSP), refined slag powder (RSP), and limestone powder (LP). First, the chemical composition of BFSP, CSP, RSP, and LP is analyzed by X-ray diffractometer (XRD) and X-ray fluorescence (XRF) tests. Then, the micromorphology characteristics of the asphalt mastic with BFSP, that with CSP, that with RSP, and that with LP are studied using atomic force microscope (AFM) tests. Finally, the rheological properties of the four asphalt mastics are investigated through dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests. The results show that steel slag powder can effectively improve the microwave sensitivity of asphalt mastic. RSP and CSP can improve the anti-deformation ability of asphalt mastic. In addition, steel slag powders have an adverse effect on the low-temperature cracking resistance of asphalt mastic, but the creep strength and creep rate of asphalt mastic with steel slag powder are within a reasonable range. In general, steel slag powder as filler has great application potential in road engineering. However, it has a certain influence on the performance of asphalt mastic. It is necessary to carry out targeted selection in practical engineering. Full article

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. Full article

OGFC (open-graded friction course) steel slag ultra-thin wearing courses are a drainage-type layer used in preventive maintenance and have been successfully applied in road construction in China. However, research on the use of steel slag in ultra-thin wearing courses has mainly focused on macroscopic volumetric indicators and performance, often overlooking the impact of internal mesoscopic void characteristics. This study utilized X-ray CT to scan OGFC ultra-thin wearing course steel slag asphalt mixtures with varying void ratios. A custom digital image processing program was developed to comprehensively and quantitatively characterize the mesoscopic void features of the mixtures from multiple perspectives, analyzing their influence on macroscopic performance. The results show that the surface void ratio and void number exhibited opposite trends with respect to specimen height. Compared to conventional asphalt mixtures, the OGFC steel slag mixtures had a higher average surface void number; the maximum difference between the maximum and minimum surface voids rate reached up to 14.2%. As the equivalent void radius and fractal dimension increased, both the stability and dynamic stability of the mixtures decreased, and the maximum reduction in Marshall stability reached 32.4%. Previous macroscopic-scale studies have struggled to identify these internal mesoscopic void characteristics, and this research provides a deeper understanding of the mesoscopic void structure in OGFC ultra-thin wearing course steel slag asphalt mixtures. Full article

This study evaluates the feasibility of reusing steel slag aggregates in asphalt concrete, analyzing the impact of different gradation methods (Bailey method and conventional Brazilian method) on the mechanical properties of the mix. Using the Marshall methodology and Petroleum Asphalt Concrete (PAC) 30/45, parameters such as Marshall stability, indirect tensile strength, resilient modulus, fatigue life through diametral compression, and permanent deformation (Flow Number) were investigated. Additionally, a simulation for a hypothetical section in the city of Rio de Janeiro, Brazil, was performed using the mechanistic-empirical pavement design software, Medina. The results showed that the mixture produced by the Bailey method outperformed the others in all analyses. This method led to a more compact mix, providing significant advantages, including up to a 35% reduction in final pavement thickness and a 110.6% increase in Flow Number (FN), enabling the mix to withstand extremely heavy traffic, as reported in the literature. Regarding fatigue life, the Bailey mixture achieved a fatigue class of 4, compared to the conventional mixture class 1. These findings indicate that using the Bailey gradation method for producing asphalt mixtures with steel slag can optimize binder content and improve resistance to permanent deformation and fatigue, making it a viable and sustainable alternative for asphalt pavements. Full article

In this study, the practical application of self-healing asphalt mixtures incorporating steel wool fibers and induction heating was investigated, expanding upon previous research that primarily assessed the self-healing properties rather than optimizing the heating process. Specifically, the aim was to enhance the induction heating methodology for a semi-dense asphalt concrete mixture (AC 16 Surf 35/50 S). In this research, the induction heating parameters were refined to improve the self-healing capabilities, focusing on the following three key aspects: (i) energy consumption, (ii) heating rate, and (iii) heating homogeneity. The findings reveal that the current intensity, the percentage of ferromagnetic additives, and coil shape are critical for achieving optimal heating conditions. Higher current intensity and additive percentage correlate with improved heating speed and reduced energy consumption. Additionally, variations in coil shape significantly influence the heating uniformity. Although asphalt mixtures with steel slag coarse aggregates exhibit slightly higher specific heat, this aggregate type is preferable for sustainability, as it allows for the recycling of industrial waste. The optimized mixtures can rapidly reach high temperatures, facilitating effective crack repair. This innovation offers a durable, environmentally friendly, and cost-effective solution for road maintenance, thereby enhancing the longevity and performance of asphalt pavements. Full article

The growing consumption of natural resources to meet the needs of road construction has become a significant challenge to environmental sustainability. Additionally, the increase in industrial by-products has raised global concerns due to their environmental impacts. The utilization of industrial by-products in asphalt mixtures offers an effective solution for promoting sustainable practices. The objective of this article is to conduct a bibliometric analysis and citation-based review to characterize and analyze the scientific literature on the use of steel slag aggregates, copper slag, phosphorus slag, bottom ash, fly ash, red mud, silica fume, and foundry sand in asphalt mixtures. Another aim is to identify research gaps and propose recommendations for future studies. The bibliometric analysis was conducted using VOSviewer software version 1.6.18, focusing on authors, co-authorship, bibliographic coupling, and countries. A total of 909 articles were selected for the bibliometric analysis. The findings indicate that more effort is needed to expand the application of industrial by-products in asphalt mixtures. Furthermore, these by-products should be utilized in different types of asphalt mixtures. The incorporation of industrial by-products into asphalt mixes also requires field validation and further laboratory investigations, particularly concerning aging and moisture resistance. In addition, the effects of chemical reactions involving industrial by-products on the long-term performance of asphalt layers should be evaluated. Finally, this article encourages engineers and researchers to intensify their efforts in utilizing industrial by-products for environmental sustainability. Full article

Ferronickel slag (FNS) is a byproduct produced during ferronickel alloy manufacturing, primarily used in the manufacturing of stainless steel and iron alloys. This material is produced by cooling molten slag with water or air, posing significant disposal challenges, as improper storage in industrial yards can lead to environmental contamination. This study investigates the chemical and mineralogical characteristics of reduction ferronickel slag (RFNS) and its potential use as an alternative aggregate in hot mix asphalt (HMA). The research is based on the practical application of HMA containing RFNS in an experimental area, specifically the parking lot used by buses transporting employees of Anglo American, located at the Codemin Industrial Unit in Niquelândia, Goiás, Central Brazil. Chemical analysis revealed that RFNS primarily consists of MgO, Fe₂O₃, and SiO₂, which are elements with minimal environmental impact. The lack of significant calcium content minimizes concerns about expansion issues commonly associated with calcium-rich slags. The X-ray diffractogram indicates a predominantly crystalline structure with minerals like Laihunite and Magnetite, which enhances wear and abrasion resistance. HMA containing 40% RFNS was tested using the Marshall methodology, and a small experimental area was subsequently constructed. The HMA containing RFNS met regulatory specifications and technological controls, achieving an average resilient modulus value of 6323 MPa. Visual inspections conducted four years later confirmed that the pavement remained in excellent condition, validating RFNS as a durable and effective alternative aggregate for asphalt mixtures. The successful application of RFNS not only demonstrates its potential for local road paving near industrial areas but also underscores the importance of sustainable waste management solutions. This research highlights the value of academia–industry collaboration in advancing environmentally responsible practices and reinforces the contribution of RFNS to enhancing local infrastructure and promoting a more sustainable future. Full article

The present study investigates the use of electric arc furnace (EAF) steel slag, a by-product of the steel industry, in asphalt pavement surface courses instead of virgin aggregates (VAs). Therefore, a general performance evaluation of such mixtures compared to conventional mixtures is carried out through laboratory and in situ tests, while both mixtures are environmentally assessed using the life cycle assessment (LCA) tool. The results of the laboratory and in situ tests show that asphalt mixtures containing granulated EAF slag aggregates perform as well as mixtures containing only VA. In addition, the LCA results show that the use of EAF slag aggregates in the asphalt surface course has a lower environmental impact than the exclusive use of VA when it comes to the impact categories of acidification, climate change, marine and terrestrial eutrophication, energy consumption and photochemical pollution. In summary, these results show that replacing virgin aggregates with a proportion of EAF slag aggregate is a viable and sustainable method for road pavement construction. Full article