Choosing medical assessments: Does the multiple-choice question make the grade?

Background: The multiple-choice question (MCQ) has been shown to measure the same constructs as the short-answer question (SAQ), yet the use of the latter persists. The study aims to evaluate whether assessment using the MCQ alone provides the same outcomes as testing with the SAQ. Methods: A prospective study design was used. A total of 276 medical students participated in a mock examination consisting of forty MCQs paired to forty SAQs, each pair matched in cognitive skill level and content. Each SAQ was marked by three independent markers. The impact of item-writing flaws (IWFs) on examination outcome was also evaluated. Results: The intraclass correlation coefficient (ICC) was 0.75 for the year IV examinations and 0.68 for the year V examinations. MCQs were more prone to IWFs than SAQs, but the effect when present in the latter was greater. Removal of questions containing IWFs from the year V SAQ allowed 39% of students who would otherwise have failed to pass. Discussion: The MCQ can test higher order skills as effectively as the SAQ and can be used as a single format in written assessment provided quality items testing higher order cognitive skills are used. IWFs can have a critical role in determining pass/fail results.

Technological advances and challenges of reclaimed asphalt pavement (RAP) application in road engineering-a bibliometric analysis from 2000 to 2022.

Reclaimed asphalt pavement (RAP) is a valuable material that can be recycled and reused in road engineering to reduce environmental impact, resource utilization, and economic costs. However, the application of RAP in road engineering presents both opportunities and challenges. This study visually analyzes the knowledge background, research status, and latest knowledge structure of literature related to RAP using scientific metric methods such as VOSviewer and Citespace. The Web of Science (WoS) core collection database identified 2963 research publications from 2000 to 2022. Collaborative networks between highly cited references, journals, authors, academic institutions, countries, and funding organizations are analyzed in this study, along with a co-occurrence analysis of keywords for the RAP research publications. Results showed that the USA has long been a leader in RAP research, China surpassed the USA in annual publication output in 2019, increasing from 2 publications in 2002 to 177 publications in 2022, and has made significant investments in technological aspects. Chang'an University ranked first in total publication output (131 publications, 4.4%). Current major research themes include road performance, recycling technology, regeneration mechanisms, and the life cycle assessment of RAP. In addition, based on cluster analysis of keywords, text content analysis, and SWOT analysis, this study also discusses RAP's challenges and future development directions in road engineering. These findings provide scholars with valuable information to gain insight into technological advances and challenges in the field of RAP.

Research on Improving Moisture Resistance of Asphalt Mixture with Compounded Recycled Metallurgical Slag Powders.

The utilization of steel slag as an alternative material in asphalt mixtures is considered the solution to the problem of the shortage of natural aggregates. However, asphalt mixtures with steel slag show susceptibility to damage caused by moisture, especially in powder form. Therefore, blast furnace slag powders were used to compound with steel slag powders as fillers to improve the moisture resistance of asphalt mixtures. The characteristics of the steel slag powders and blast furnace slag powders were investigated initially. Subsequently, the adhesion properties of the asphalt mastics with the powders to the aggregates were evaluated. Finally, the moisture resistances of the asphalt mixtures were identified. The results indicate that the steel slag powder exhibited a notable prevalence of surface pores, which had a more uniform size distribution. In contrast, the blast furnace slag powder exhibited a greater average pore size. The larger specific surface area of the steel slag powder was over 30% larger than that of the blast furnace slag powder, and the superior gelling activity of the blast furnace powder enhanced the adhesion property. Both the steel slag powder and blast furnace slag powder were found to enhance the adhesion properties of the asphalt mastics, while the effect of the steel slag powder was more pronounced, the maximum force difference of which exceeded 200 N. The antagonistic effect of the steel slag powder and blast furnace slag powder on the resistance of the adhesive interface to moisture damage was confirmed by the contact angle test. The incorporation of the blast furnace slag powder markedly enhanced the moisture resistances of the asphalt mixtures. The phenomenon of dynamic moisture damage to the asphalt mixtures was more pronounced under the multicycle times, obviously severer than that in a stable water environment. As the dynamic moisture cycles increased, the degree of destruction gradually approached a steady state.

The Production of Porous Asphalt Mixtures with Damping Noise Reduction and Self-Healing Properties through the Addition of Rubber Granules and Steel Wool Fibers.

Conventional asphalt roads are noisy. Currently, there are two main types of mainstream noise-reducing pavements: pore acoustic absorption and damping noise reduction. However, a single noise reduction method has limited noise reduction capability, and porous noise-reducing pavements have a shorter service life. Therefore, this paper aimed to improve the noise-damping performance of porous asphalt mixture by adding rubber granules and extending its service life using electromagnetic induction heating self-healing technology. Porosity and permeability coefficient test, Cantabro test, immersion Marshall stability test, freeze-thaw splitting test, a low-temperature three-point bending experiment, and Hamburg wheel-tracking test were conducted to investigate the pavement performance and water permeability coefficients of the mixtures. A tire drop test and the standing-wave tube method were conducted to explore their noise reduction performance. Induction heating installation was carried out to study the heating rate and healing performance. The results indicated that the road performance of the porous asphalt mixture tends to reduce with an increasing dosage of rubber granules. The road performance is not up to the required standard when the dosage of rubber granules reaches 3%. The mixture's performance of damping and noise tends to increase with the increase of rubber granule dosage. Asphalt mixtures with different rubber granule dosages have different noise absorption properties, and the mixture with 2% rubber granules has the best overall performance (a vibration attenuation coefficient of 7.752 and an average absorption factor of 0.457). The optimum healing temperature of the porous asphalt mixture containing rubber granules and steel wool fibers is 120 °C and the healing rate is 74.8% at a 2% rubber granule dosage. This paper provides valuable insights for improving the noise reduction performance and service life of porous asphalt pavements while meeting road performance standards.

Research Progress in the Development of Vaccines against Mycoplasma gallisepticum and Mycoplasma synoviae.

Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS) are the primary agents responsible for mycoplasma disease in poultry. MG has been identified as a significant cause of chronic respiratory disease in chickens, while MS has been linked to the development of tenosynovitis, joint swelling and other symptoms in chickens, leading to considerable economic losses for the poultry industry. Unfortunately, there is no specific drug for treatment and vaccination is the most important way to control the disease. There are some different types of vaccines, including live vaccines, inactivated vaccines, sub-unit vaccines and vector vaccines. This paper provides a comprehensive review of the development of vaccines for MG and MS.

Research on the Mechanical, Thermal and Induction Healing Properties of Asphalt Wearing Course with Steel Fibers.

Induction healing technology can effectively repair microcracks in asphalt mixtures and is a promising maintenance technology for asphalt pavements. However, it requires the addition of steel wool fibers to asphalt mixtures and cannot be directly used to repair existing pavements. In order to improve the practicality of the induction healing technology, this article designs a wearing course asphalt mixture with induction healing function that is going to be paved above the existing road surface. The AC-10 asphalt wearing course for induction heating was prepared by adding steel fiber (SF). Analysis of the overall temperature of the surface revealed the unevenness of the temperature distribution, and the healing properties were investigated through protective heating that controlled the maximum temperature of the upper surface. The results show that the addition of SF can improve the high-temperature stability, low-temperature and intermediate-temperature crack resistance, and moisture stability of asphalt wearing courses; however, it has adverse effects on volumetric performance and skid resistance. The heating temperature increases with the increase in SF content, but higher maximum temperature heating rate causes worse heating uniformity and lower healing effect. The maximum heating rate of the sample with 10% SF reaches 3.92 °C/s, while its heating rate at minimum temperature is similar to that of the sample with 6% SF, which is only 0.7 °C/s, indicating the worst heating uniformity. The best healing effect occurs when the maximum temperature of the upper surface reaches 160 °C. The recommended optimal SF content is 6% of the asphalt volume. The asphalt mixture with 6% SF has an appropriate volume performance, moisture stability, and skid resistance; additionally, it has the best high-temperature stability, as well as low-temperature and intermediate-temperature crack resistance. Meanwhile, it also has uniform temperature distribution and efficient healing efficiency.

Pathogenicity of Multidrug-Resistant Salmonella typhimurium Isolated from Ducks.

Salmonella typhimurium (S. typhimurium) is one of the most common Salmonella serotypes in epidemiological surveys of poultry farms in recent years. It causes growth retardation, mortality, and significant economic losses. The extensive use of antibiotics has led to the emergence of multi-drug resistance (MDR) in Salmonella, which has become a significant global problem and long-term challenge. In this study, we investigated the prevalence and features of S. typhimurium strains in duck embryos and cloacal swabs from large-scale duck farms in Shandong, China, including drug resistance and virulence genes and the pathogenicity of an S. typhimurium strain by animal experiment. The results demonstrated that a total of 8 S. typhimurium strains were isolated from 13,621 samples. The drug resistance results showed that three of the eight S. typhimurium strains were MDR with the dominant resistance profile of CTX-DX-CTR-TE-AMX-AMP-CAZ. In particular, the virulence genes invA, hilA, pefA, rck, and sefA showed high positive rates. Based on the analysis of the biological characteristics of bacterial biofilm formation and mobility, a strain of S. typhimurium with the strongest biofilm formation ability, designated 22SD07, was selected for animal infection experiments with broiler ducklings. The results of animal experiments demonstrated that infection with 22SD07 reduced body weight and bursa index but increased heart and liver indexes compared to the control group. Histological examination revealed desquamation of the intestinal villous epithelium, the presence of large aggregates of lymphocytes, and a decrease in goblet cells following infection. Furthermore, the expression of IL-10 was significantly increased in the liver at 3 dpi, while TNF-α was significantly increased in the spleen at 7 dpi. The above results indicate that S. typhimurium may pose a potential threat to human health through the food chain. This helps us to understand the frequency and characteristics of S. typhimurium in duck farms and emphasizes the urgent need to strengthen and implement effective continuous monitoring to control its infection and transmission.

The Rejuvenation Effect of Bio-Oils on Long-Term Aged Asphalt.

Generally, rejuvenators are used to supply missing components of aged asphalt, reverse the aging process, and are widely used in asphalt maintenance and recycling. However, compared with traditional rejuvenators, bio-oil rejuvenators are environmentally friendly, economical and efficient. This study looks into the effect of the three different bio-oils, namely sunflower oil, soybean oil, and palm oil, on the physical properties, rheological properties and chemical components of aged asphalt at different dosages. The asphalt physical properties and Dynamic Shear Rheological (DSR) test results show that with the increase in bio-oil, the physical properties and rheological properties of rejuvenated asphalt are close to those of virgin asphalt, but the high-temperature rutting resistance needs to be further improved. The results of Fourier Transform Infrared Spectroscopy (FTIR) show that the carbonyl and sulfoxide indices of rejuvenated asphalt are much lower than those of aged asphalt. Moreover, the rejuvenation efficiency of aged asphalt mixed with sunflower oil is better than that with soybean oil and palm oil at the same dosage.

Quantitative analysis and environmental assessments of gaseous inorganic compounds in Asphalt fume.

The Volatile Organic Compounds (VOCs) in asphalt fume is widely concerned currently due to its biological toxicity, while the negative effects by asphalt Gaseous Inorganic Compounds (GICs) have not been well quantified and addressed yet. The study investigated the thermodynamic characteristics of base and modified asphalt binders during the multiple phases of releasing the GICs, then the releasing amounts and concentrations of GICs were quantified by fume analyzer. Meanwhile, the environmental impacts of GICs from 4 kinds of asphalt binders have been quantified and interpreted. The results showed that the modified asphalt released less proportion of GICs than base asphalt as heated by same thermal condition according to the TG-DTG and enthalpy analysis. Considering 1 g of asphalt sample, the base asphalt could release extra 8 mg of GICs than modified asphalt, additionally, the emissions of NO2, NO, CO2, and SO2 are all less than the mass of 1 mg. For the environmental effects, the releasing GICs had the greatest impacts on human toxicity due to the intensive CO emission. These results are expected to provide reference and new insights into the improvement of asphalt fumes mitigation.

A motif for B/O-site modulation in LaFeO3 towards boosted oxygen evolution.

Here, a series of transition metal (Ni) doped iron-based perovskite oxides LaFe1-xNixO3-δ (x = 0, 0.25, 0.5, 0.75, 1) were prepared, and then the perovskite oxide with the optimized nickel-iron ratio was doped with non-metallic elements (N). Experimental and theoretical investigations reveal that the co-doping breaks the traditional linear constraint relationship (GOOH - GOH = 3.2 eV) and the theoretical overvoltage is reduced from 0.64 V (LaFeO3-δ) to 0.44 V (LaFe0.5Ni0.5O3-δ/N). Specifically, Ni-doping can accelerate electron transfer and improve the conductivity. Moreover, N-doping can reduce the adsorption energy of *OH/*O and enhance the adsorption energy of *OOH. We demonstrated that the optimized cation and anion co-doped LaFe0.5Ni0.5O3-δ/N perovskite oxide exhibits an excellent OER performance, with a low overpotential of 270.6 mV at 10 mA cm-2 and a small Tafel slope of 65 mV dec-1 in 1 M KOH solution, markedly exceeding that of the parent perovskite oxide LaFeO3-δ (300.9 mV) and commercial IrO2 (289.1 mV). It also delivers decent durability with no significant degradation after a 35 h stability test. This work reveals the internal mechanism of perovskite oxide by doping cation and anion for water oxidation, which broadens the idea for the rational design of new perovskite-based sustainable energy catalysts.

A quadruplex real-time PCR assay combined with a conventional PCR for the differential detection of Marek's disease virus vaccines and field strains.

To evaluate the effect of the vaccine and differentiate vaccine from virulent MDV, a new quadruplex real-time PCR assay based on TaqMan probes was developed to differentiate and accurately quantify HVT, CVI988 and virulent MDV-1. The results showed that the limit of detection (LOD) of the new assay was 10 copies with correlation coefficients >0.994 of CVI988, HVT and virulent MDV DNA molecules without cross-reactivity with other avian disease viruses. The intra-assay and inter-assay coefficients of variation (CVs) of Ct values for the new assay were less than 3%. Analysis of replication kinetics of CVI988 and virulent MDV of collected feathers between 7 and 60 days post-infection (dpi) showed MD5 had no significant effect on the genomic load of CVI988 (p > 0.05), while vaccination with CVI988 could significantly reduce the viral load of MD5 (p < 0.05). Combined with meq gene PCR, this method can effectively identify virulent MDV infections in immunized chickens. These results demonstrated that this assay could distinguish between the vaccine and virulent MDV strains and had the advantages of being reliable, sensitive and specific to confirm the immunization status and monitor the circulation of virulent MDV strains.

Experimental Study on the Physicochemical Properties of Asphalt Modified by Different Anti-Stripping Agents and Their Moisture Susceptibility with Aggregates.

Erosion and the stripping effect of moisture on asphalt mixtures is one of the main reasons for the shortened service life of asphalt pavements. The common mean of preventing asphalt pavements from being damaged by moisture is adding anti-stripping agents (ASAs) to asphalt mixtures. However, the effect regularity and mechanism of anti-stripping agents on the physicochemical properties of asphalt is not exactly defined. This study compared the physical properties of ASA-modified asphalt (AMAs) to determine the optimal dosage and investigated the rheological and adhesion properties. Based on the roller bottle method and water immersion method, the moisture susceptibility of AMAs with three particle sizes was investigated. The results showed that the modification of asphalt using anti-stripping agents was a physical modification. At the optimum dosage of anti-stripping agents (0.3%), the basic physical properties of AMA1 were the most desirable. ASA2 increased the resistance of asphalt for deformation at high temperature by 46%, and AMA3 had the best low-temperature performance. ASAs enhanced the dispersed and polar components in the asphalt binder, improving the adhesion energy of asphalt. AMA3 had the strongest adhesion to the aggregate, with an increase in adhesion work by 2.8 times and a 45% of increase in ER value. This was attributed to ASA3 containing with a large number of metal cations and polar functional groups. It was shown that ASAs provided the most improvement in the anti-stripping performance of asphalt mixtures with 9.5-13.2 mm particles. The amide ASA, phosphate ASA and aliphatic amine ASA improved the water damage resistance of asphalt by 65%, 45% and 78%, respectively. This study can help engineers realize the effects of different types of ASAs on the physicochemical properties of asphalt and select the most suitable type of ASAs according to the service requirements.

Characteristics, Whole-Genome Sequencing and Pathogenicity Analysis of Escherichia coli from a White Feather Broiler Farm.

Avian colibacillosis, caused by avian Escherichia coli (E. coli), has historically been one of the most prevalent infectious diseases in large-scale poultry production, causing growth delays and mortality in chickens, resulting in huge economic losses. In recent years, the widespread use of antibiotics has led to the emergence of multidrug resistance in E. coli as a significant global problem and long-term challenge. Resistant E. coli can be transmitted to humans through animal products or the environment, which presents significant public health concerns and food safety issues. In this study, we analyzed the features of 135 E. coli strains obtained from a white feather broiler farm in Shandong, China, including antimicrobial susceptibility tests, detection of class 1 integrons, drug resistance genes, virulence genes, and phylogenetic subgroups. It is particularly worrying that all 135 E. coli strains were resistant to at least five antibiotic agents, and 100% of them were multidrug-resistant (MDR). Notably, the resistance genes of blaTEM, blaCTX-M, qnrS, aaC4, tetA, and tetB exhibited a high prevalence of carriage among the tested resistance genes. However, mcr-2~mcr-9 were not detected, while the prevalence of mcr-1 was found to be 2.96%. The most common virulence genes detected were EAST1 (14.07%, encoding enterotoxins) and fyuA (14.81%, encoding biofilm formation). Phylogenetic subgroup analysis revealed that E. coli belonging to groups B2 and D, which are commonly associated with high virulence, constituted 2.22% and 11.11%, respectively. The positive rate of class 1 integrons was 31.1%. Whole-genome sequencing (WGS) and animal experiments were performed on a unique isolated strain called 21EC78 with an extremely strong membrane-forming capacity. The WGS results showed that 21EC78 carried 11 drug resistance genes and 16 virulence genes. Animal experiments showed that intraperitoneal injection with 2 × 105 CFU could cause the death of one-day-old SPF chickens in 3 days. However, the mortality of Luhua chickens was comparatively lower than that of SPF chickens. This study reports the isolation of multidrug-resistant E. coli strains in poultry, which may pose a potential threat to human health via the food chain. Furthermore, the findings of this study enhance our comprehension of the frequency and characteristics of multidrug-resistant E. coli in poultry farms, emphasizing the urgent need for improved and effective continuous surveillance to control its dissemination.

Bionic Synthesis of Mussel-like Adhesive L-DMA and Its Effects on Asphalt Properties.

Cracks are inevitable during the service life of asphalt pavement and the water at the fracture surfaces tends to cause the grouting materials to fail. Studies have shown that the catechol groups in adhesion proteins secreted by mussels can produce strong adhesion performance in the water. In this paper, the mussel-like adhesive L-Dopa Methacrylic anhydride (L-DMA) was prepared based on the concept of bionic design and used to improve the properties of asphalt. By using Fourier-transform infrared spectroscopy (FTIR) and Thermogravimetric analysis (TGA), the thermal stability and structural composition of L-DMA were investigated. Then, the rheological and low-temperature properties of L-DMA-modified asphalt were investigated using the dynamic shear rheological (DSR) test and bending beam rheological (BBR) test. Moreover, the modification mechanism was explored by FTIR. It was found that L-DMA can be effectively synthesized and has good thermal stability. The incorporation of L-DMA increases the composite modulus, viscosity, creep recovery rate and rutting factor of asphalt binder, resulting in an enhancement of its high-temperature performance. At a high L-DMA content of 10%, the low-temperature performance of the modified asphalt was enhanced. The modification of L-DMA to asphalt is mainly a physical process. Hydrogen bonds and conjugated systems generated by the introduction of catechol groups enhance the adhesion properties of asphalt. In general, L-DMA improves the properties of asphalt and theoretically can improve the water resistance of asphalt, which will be explored in future research.

The Mechanical Resistance of Asphalt Mixture with Steel Slag to Deformation and Skid Degradation Based on Laboratory Accelerated Heavy Loading Test.

Steel slag is a main form of solid waste. Using this component to replace part of the aggregate in an asphalt mixture is an effectively way of treating solid waste. To study the performance degradation of asphalt mixture with various content of steel slag under heavy loading, some large-sized basalt hot mixed asphalt mixture (BHMA) and steel slag hot mixed asphalt mixture (SHMA) in a form of specimens were prepared and a heavy loading wheel tracking test was conducted. The aggregate characteristics of basalt and steel slag were measured. The deformation and skid resistance of the asphalt mixture with different content of steel slag was tested and analyzed. Due to the particle characteristics of steel slag aggregate, it was found that a low content of steel slag can effectively improve the resistance to deformation and skid resistance of the asphalt mixture under heavy loading. The response of SHMA can still meet the pavement technical requirement after long-term heavy loading service. The main change in the mixture under heavy loading is the crushing of the 9.5-16 mm aggregate, and the content of this part also significantly affects the deformation. This study explains the mechanism of degradation of SHMA under heavy loading: the large aggregate is crushed and forms a new aggregate skeleton structure.

Influence of catalyst and solvent on the hydrothermal liquefaction of woody biomass.

Hydrothermal liquefaction of woody biomass with catalysts was commonly applied in bio-energy research, but the effects of catalyst and solvent on yield and properties of bio-energy are not clear. In this work, the influences of catalyst and solvent on bio-energy production were studied, during which four solvents and three catalysts were used, and the liquefaction parameters were optimized by experimental and Machine learning (ML) method. Results show that the maximum yields of bio-oil and biochar are 65.0% and 32.0%, respectively, and the caloricvalues of bio-oil and biochar are 31.2 MJ/kg and 26.5 MJ/kg, respectively. Alkaline catalysts and 1,4-butanediol-triethanolamine mix solvent can benefit the bio-energy generation. In addition, a Random Forest (RF) was developed to forecast the yields, and the method performed well with experimental results.

Effects of Low-Temperature Construction Additives (LCAs) on the Performance of Asphalt Mixtures.

Green production of asphalt materials is very important to promote energy savings and emission reduction during the construction and maintenance of asphalt pavement. A low-temperature construction additive (LCA) made from the waste plastic and waste rubber is proposed, which belongs to a class of environmentally friendly additives for asphalt mixtures. Marshall stability was tested to evaluate the mechanical performance of LCA-modified asphalt mixtures (LCA-AMs). In order to determine the best preparation parameters of LCA-AMs, the influence of the content and LCA addition method on the strength of LCA-AMs was studied. In addition, the impact of epoxy resin (ER) on the mixtures' performances was evaluated. The results show that the LCA can significantly reduce the formation temperature of asphalt mixtures, and the resulting asphalt mixtures have good workability in a lower temperature range (90-110 °C). The ER should be added to the LCA-AMs after 4 h of curing. All the volumetric properties satisfy the technical requirements. The low-temperature crack resistance and fatigue resistance of LCA-AMs were obviously improved with appropriate dosages of ER, which can effectively improve the mechanical performance of the asphalt mixtures. The ER can significantly increase the rutting resistance and water sensitivity of LCA-AMs, therefore making it feasible to improve the mixture performance by the enhancement provided by a low dosage of ER.

Physical Properties and Storage Stability of Buton Rock Asphalt Modified Asphalt.

Buton Rock Asphalt (BRA) refers to the natural rock asphalt natively produced on the Buton island of Indonesia. It is often used as a modifier to enhance the performance of asphaltpavement. However, the segregation of BRA in BRA-Modified Asphalt (BRA-MA) has restricted its application. This study aims to investigate how the particle size and content of BRA affect the physical properties and storage stability of BRA-MA. Penetration, softening point, viscosity, and viscosity-temperature susceptibility (VTS) were analyzed. The evaluation method of storage stability was discussed and determined. The segregation of BRA in BRA-MA of static storage and transportation process were simulated and tested. The results suggest that the softening point and viscosity were positively correlated to BRA content and inversely determined by particle size. Penetration, VTS, and ductility were reduced due to the decline in particle size and increment of BRA content. The index of segregation value based on viscosity difference showed better statistical and quantitative significances than the softening-point difference in evaluating the storage stability. The particle size and content of BRA are positively correlated to the segregation of BRA-MA. Both the storage temperature and time were positively correlated to the segregation of BRA-MA. We prove that the relationship between specific surface area and segregation are power functional. BRA-MA with BRA whose 50% particle sizes are lower than 13.6 µm showed low segregation in transportation.

Optimization of Asphalt-Mortar-Aging-Resistance-Modifier Dosage Based on Second-Generation Non-Inferior Sorting Genetic Algorithm.

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 x1 were 2.15%, 1.0%, and 1.1%, respectively, while the corresponding dosage of x2 were 0.25%, 0.76%, and 0.38%, respectively. The optimal value of the modifier dosage x1 was 1.2% and x2 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.

Quantitative Assessment of Road Performance of Recycled Asphalt Mixtures Incorporated with Steel Slag.

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.