Reutilization of reclaimed asphalt pavement (RAP) is conducive to achieving carbon peak and neutrality goals and establishing a resources recycling system for road engineering. Previous studies have ...indicated that recycled asphalt mixtures with RAP content exceeding 30% seem inappeasable in upper surface of asphalt pavement due to their inferior skid resistance and endurance. While steel slag, a solid waste with excellent mechanical properties and high alkalinity, can elevate performances of asphalt mixture. Recycled asphalt mixtures involving 50%, 60% and 70% RAP content and steel slags were prepared firstly, and their road performances were characterized. Properties discrepancies existing in microstructure and geometric characteristics of steel slag and basalt and their interfacial properties with asphalt were discussed. The results indicate that incorporating steel slag in recycled asphalt mixtures with 70% RAP content reveals a desirable performances indexes in contrast to basalt. The adhesion and mechanical performance of recycled asphalt mixtures can be significantly enhanced by steel slag due to its honeycomb porous structure, larger angularity, lower sphericity and higher texture. Steel slag and recycled asphalt demonstrate lower spalling rate under hydrodynamic pressure and larger adhesive destructive force compared with basalt, resulting in superior moisture susceptibility and cracking resistance for recycled asphalt mixtures.
For the sustainable development of society, recycling of solid waste has received considerable attention worldwide. In this research, steel slag was used to replace natural aggregate in the thin ...asphalt overlay, and the hazardous characteristics and internal microstructure of this overlay were explored. The resistance to hydrodynamic damage of the overlay containing steel slag was also evaluated and compared with that of the traditional overlay. The results indicate that steel slag has potential leaching risk, which can lead to environmental hazards in long-term leaching processes. However, the recycling of steel slag in thin asphalt overlay inhibits the release of toxic heavy metals due to the encapsulation effect, thereby reducing the leaching concerns. Steel slag can significantly reinforce the skeleton structure and enhance the ability of the asphalt overlay to bear the load. The superior skeleton stability and moisture resistance of the steel slag asphalt overlay were observed after hydrodynamic treatment compared with overlays made of natural aggregate. The variations in the volumetric parameters and connectivity in the steel slag asphalt overlay are significantly less than those in conventional overlay after hydrodynamic treatment. This indicates that the volumetric characteristics of steel slag asphalt overlays are less affected by hydrodynamic pressure.
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•Hazardous characteristics and microstructure of overlays were explored.•Recycling steel slag in overlays can inhibit the release of heavy metal ions.•The microstructure stability of the overlay was enhanced by steel slag.
Micro-surfacing is a widely used pavement preventive maintenance technology used all over the world, due to its advantages of fast construction, low maintenance cost, good waterproofness, and ...skid-resistance performance. This study evaluated the fine aggregate morphology and surface texture of micro-surfacing by AIMS (aggregate image measurement system), and explored the effect of aggregate morphology on skid-resistance of single-grade micro-surfacing. Sand patch test and British pendulum test were also used to detect skid-resistance for comparison with the image-based method. Wet abrasion test was used to measure skid-resistance durability for feasibility verification of single-grade micro-surfacing. The results show that the effect of Form2D on the skid-resistance of micro-surfacing is much stronger than that of angularity. Combining the feasibility analysis of durability and skid-resistance, 1.18⁻2.36 grade micro-surfacing meets the requirements of durability and skid-resistance at the same time. This study also determined that, compared with British pendulum test, the texture result obtained by sand patch test fits better with results of image method.
The commonly used materials in fog seal are emulsified asphalt and modified emulsified asphalt. Nevertheless, there are some intractable problems including aging under ultraviolet, poor permeability, ...and moisture susceptibility. Therefore, silicone resin polymer was used as a kind of innovative fog seal material in this study. Physicochemical properties of solidified silicone resin were characterized. X-ray computed tomography and 3D reconstruction technology were used to evaluate permeability and distribution of silicone resin polymer in an asphalt mixture. Moisture sensitivity and high-temperature performance of the asphalt mixture maintained by silicone resin polymer were also detected. The results show that surface characteristic of silicone resin can effectively isolate moisture, thereby improving moisture resistance of the asphalt mixture. Silicone resin was found to be evenly distributed throughout the pores of a sample when the dosage was 400 or 600 mL/m
. The pore filling rate increased by 16.3% when the dosage was changed from 200 to 400 mL/m
, whereas it only increased by 3.7% when dosage increased from 400 to 600 mL/m
. Moisture damage resistance of asphalt mixtures generally increased as the dosage of silicone was increased. However, as the dosage increased from 400 to 600 mL/m
, the growth rate in residual Marshall stability (RMS) and tensile strength ratio (TSR) slowed significantly since the pore filling effect of silicone has reached the upper limit. Dosage of silicone resin has little effect on the results of the rutting test while it has significant influence on Hamburg wheel tracking test (HWT). Furthermore, it was found that 400 mL/m
is the optimum silicone dosage for open-graded friction course (OGFC)-13 mixture in consideration of permeability, distribution, performance of mixture, and economic cost.
Micro-surfacing (MS), made of emulsified asphalt, is the most commonly used preventive maintenance technology in asphalt pavement. However, the studies on profile features of MS based on aggregate ...morphology are few. This study evaluated the profile features of MS and its effect on skid resistance. The aggregate morphologies were first characterized and modified emulsified asphalt was prepared. The three-dimensional profile features of four kinds of MS samples were captured by laser texture scanner. Results illustrate that steel slag aggregate can be used to enhance the skid resistance of pavement surface and bring about larger profile indexes than basalt and limestone due to its angularity index and flatness values. Further aging of steel slag to eliminate free calcium oxide (f-CaO) is recommended before being used in pavement surface layer.
To promote the comprehensive utilization of solid waste in highway engineering, asphalt rubber hot mixture (ARHM-13) was prepared with steel slag and SBS/CR modified asphalt. The pavement performance ...of steel slag and basalt asphalt mixtures, including Marshall stability, moisture susceptibility, high temperature and low temperature performance, were evaluated in the laboratory. Combined with the project case of the trial pavement section in Beijing-Qinhuangdao Expressway, and the compactness, flatness, skid resistance and seepage resistance of the asphalt pavements were tested. And volatile organic compounds (VOCs) emissions and economic performance of asphalt mixtures were analyzed. The results showed that steel slag asphalt mixture reveals more excellent pavement performance than basalt asphalt mixture. The compactness, skid resistance and anti-seepage performance of asphalt mixture with steel slag are superior than basalt in contrast to the surface flatness. The VOCs emission concentrations of the steel slag asphalt mixture during mixing plant, spreading and rolling are higher than that of basalt asphalt mixture. Replacing basalt with steel slag can reduce by about 56.7% of aggregate cost and increase by 6.2% of asphalt cost. The total cost of raw materials for 1 km asphalt mixture with steel slag is reduced by about 10.5%. The research conclusion of this study provides the theoretical support for the promotion and utilization of steel slag and crumb rubber in road engineering.
Asphalt pavement is widely used for expressways due to its advantages of flexibility, low cost, and easy maintenance. However, pavement failures, including cracking, raveling, and potholes, will ...appear after long-term service. This research evaluated the residual fatigue properties of asphalt pavement after long-term field service. Fatigue behavior of specimens with different pavement failure types, traffic load, service time, and layers were collected and characterized. Results indicate that after long-term field service, surface layer has a longer fatigue life under small stress levels, but shorter fatigue life under large stress levels. Longer service time results in greater sensitivity to loading stress, while heavier traffic results in shorter fatigue life. Surface and underneath layers present very close fatigue trend lines in some areas, indicating that the fatigue behavior of asphalt mixture in surface and underneath layers are aged to the same extent after eight to ten years of field service.
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.
The use of steel slag powder instead of filler to prepare asphalt mortar was beneficial to realize the effective utilization of steel slag and improve the performance of asphalt concrete. ...Nevertheless, the anti-aging properties of steel-slag powder-asphalt mortar need to be further enhanced. This study used antioxidants and UV absorbers in steel-slag powder-asphalt mortar to simultaneously improve its thermal-oxidation and UV-aging properties. The dosage of modifier was optimized by second-generation non-inferior sorting genetic algorithm. Fourier-Transform Infrared Spectroscopy, a dynamic shear rheometer and the heavy-metal-ion-leaching test were used to evaluate the characteristic functional groups, rheological properties and heavy-metal-toxicity characteristics of the steel-slag-powder-modified asphalt mortar, respectively. The results showed that there was a significant correlation between the amount of modifier and G*, δ, and the softening point. When the first peak appeared for G*, δ, and the softening point, the corresponding dosages of
were 2.15%, 1.0%, and 1.1%, respectively, while the corresponding dosage of
were 0.25%, 0.76%, and 0.38%, respectively. The optimal value of the modifier dosage
was 1.2% and
was 0.5% after weighing by the NSGA-II algorithm. The asphalt had a certain physical solid-sealing effect on the release of heavy-metal ions in the steel-slag powder. In addition, the asphalt structure was changed under the synergistic effect of oxygen and ultraviolet rays. Therefore, the risk of leaching heavy-metal ions was increased with the inferior asphalt-coating performance on the steel-slag powder.
Steel slag, the by-product of steelmaking, is a desirable alternative material for natural aggregate. However, there are few studies applying steel slag in the preventive maintenance of asphalt ...pavements, especially chip seal. The main objective of this study is to explore the feasibility of applying steel slag in chip seal and the effect of steel slag on the thermal exchange and aggregate retention properties. Furthermore, the surface features, including texture depth and skid resistance. of chip seal were also evaluated. The results show that the thermal exchange performances of chip seal vary with aggregate types. The ranking of the chip seal samples according to the cooling rate places ferrochromium (FER) slag as the fastest and basic oxygen furnace (BOF) slag as the slowest, with the basalt (BS) falling in between. The use of FER slag can make the chip seal resume traffic about ten minutes earlier than original samples. The skid resistance and texture depth of FER slag meet the requirements of the specification, although they are less than those of ordinary aggregates. Moreover, FER slag has a better aggregate retention performance than BOF slag and BS due to its spherical particles and alkaline surface. The application of steel slag in chip seal can recycle industrial waste, reduce the consumption of natural resources and promote economic pavement maintenance technology.
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