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Past studies broadly discussed the effect of sulfur on the rheological properties of styrene–butadiene–styrene (SBS) modified asphalt, while the relationships between the rheological properties and phase behaviour of SBS-modified asphalt after sulfur vulcanisation have received less attention, which limits the further understanding of the relations between the structure and performance. To this end, this paper is aimed to discuss viscoelastic response at the molecular level and reveal the enhancement mechanism of SBS-modified asphalt after adding sulfur. Thus, the morphology, phase structure, and rheological behaviour of SBS/Sulfur modified asphalt were investigated by experimental assessment and molecular dynamics. Based on the results, it was found that the polybutadiene segments in SBS copolymer are the leading reactive site of vulcanisation, the interactions between SBS copolymer and light components were enhanced by sulfur treatment, the orderliness of asphalt molecules in SBS/sulfur modified asphalt was strengthened, and SBS copolymer presents a stronger attraction to aromatic after vulcanisation, which means the increase of boundary layer is also the significant cause to the improvement of compatibility. The findings are expected to deepen understanding of the vulcanisation mechanism and the rheological behaviour of SBS/Sulfur modified asphalt. [ABSTRACT FROM AUTHOR]

Detection of the tie bars in concrete pavement has been a challenging task. To address the purpose, ground penetrating radar (GPR) was used to acquire a large amount of image data along the longitudinal construction joints of plain concrete pavement in the field. The GPR image data was filtered to construct the dataset, containing 2185 tie bar reflected waves in 670 GPR images. Then, the YOLO series models, as the deep learning algorithms applied in inspecting the tie bars from GPR images, were well trained with the GPR training and validation sets. The comprehensive detection accuracy of the YOLOv4 model outperforms the YOLOv3, YOLOv3-tiny, and YOLOv4-tiny models in the test set. The mAP@0.5 value of the YOLOv4 model can reach 99.74%. All the signatures of tie bars in the testing GPR images, no matter whether they are incomplete, compressed, blurry with missing signal, or strong background noise, can be correctly and completely anchored using the bounding box based on the YOLOv4 model. Meanwhile, the detection speed of the YOLOv4 model for GPR data video is 50.8 frames per second. Therefore, the YOLOv4 model is reliable for automatically detecting the tie bars from GPR data in real-time. [ABSTRACT FROM AUTHOR]

In order to solve the problem of frequent snow and ice removal in winter, a micro-surfacing pavement with active snow and ice removal and slow-release function is developed. The snow-melting agent with sodium acetate, calcium acetate, and potassium acetate as the main components was prepared, and the optimum proportion was determined. With the help of hygroscopicity and oil absorption tests, the optimum surface modifier and its optimum concentration were determined. The microstructure of the snowmelt agent were characterized by infrared spectroscopy and scanning electron microscopy. The influence of snow-melting agent on the road performance was explored. The results show that the optimum proportion of sodium acetate, calcium acetate and potassium acetate is 37, 15 and 48 % respectiveiy. When the surface modifier: hydrogen silicone oil and KH560 solution concentration was 4.0% and 1.0% respectively, the slow-release effect was the optimum. The wear resistance and high temperature stability of micro-surfacing with the snowmelt agent were increased by 2.5 % and 8.2 %, respectively. It is most reasonable to determine that the optimal replacement amount of mineral powder is 50%. It is necessary to study the distribution of self-made snowmelt agent in the mixture in the future. [ABSTRACT FROM AUTHOR]

The chemical–physical hybrid cross-linked double network gel poly (acrylamide-co-acrylic acid)/Sodium alginate/Fe3+ (P(AM-co-AA)/SA/Fe3+, simplified as P-gel) was synthesised by free radical polymerisation combined with hydrogen bonding and ion coordination, which was in turn compounded with styrene–butadiene-styrene (SBS) to prepare P-gel gel/SBS modified asphalt. FT-IR, UV, XRD and SEM analyses confirmed the successful synthesis of P-gel. FM analysis revealed that the volume of P-gel increased after the long-term aging of asphalt. The physical, Dynamic Shear Rheometer (DSR), multi-stress creep recovery (MSCR), and time sweep tests showed that the addition of P-gel improved the road performance of the SBS modified asphalt. At a P-gel amount of 5%, the high-temperature performance grade (PG high temperature) of SBS modified asphalt improved from PG70 to PG76 and the recovery rate (64 oC) was increased by 17.08% and 41.13% at the stress of 0.1 and 3.2 kPa, respectively. The underlying mechanism behind these improvements in the mechanical properties of the composite modified asphalt was the different competitive relationship between the 'softening' effect of P-gel in asphalt and the 'strengthening' effect of the asphalt itself at different temperatures. This project provides an alternative strategy for preparing P-gel gel/SBS modified asphalt with enhanced mechanical properties for applications in the highway and construction industries. [ABSTRACT FROM AUTHOR]

The patch recognition and localisation from high-resolution pavement images play a key role in evaluating asphalt pavement condition. To achieve the purpose, two line-scan cameras were employed to acquire lots of full-scale asphalt pavement images with 1 mm2 per pixel resolution in the field. The raw images were pre-processed to construct the dataset, including 984 patches of various shapes in 827 pavement images. Subsequently, the YOLO series models innovatively applied in automatically detecting the patches from pavement images were well trained with the pavement training and validation sets. The testing results reveal that the F1-score and mAP@0.5 values of the YOLOv4 model are 0.911 and 92.92% respectively in the test set. The comprehensive recognition accuracy of the YOLOv4 model outperforms the other YOLO models. And the detection speed of the YOLOv4 model for pavement data video is 38.1 frames per second. Additionally, all the features of patches in the partial testing pavement images, no matter whether they are strip, block, intersection, blurry within the shadow, or background noise, can be correctly predictedby the rectangular box. The average localisation errors of the width and height of the predicted patches are 21 and 16 mm respectively, and the average IoU is 0.83. [ABSTRACT FROM AUTHOR]

The patch recognition and localisation from high-resolution pavement images play a key role in evaluating asphalt pavement condition. To achieve the purpose, two line-scan cameras were employed to acquire lots of full-scale asphalt pavement images with 1 mm2 per pixel resolution in the field. The raw images were pre-processed to construct the dataset, including 984 patches of various shapes in 827 pavement images. Subsequently, the YOLO series models innovatively applied in automatically detecting the patches from pavement images were well trained with the pavement training and validation sets. The testing results reveal that the F1-score and mAP@0.5 values of the YOLOv4 model are 0.911 and 92.92% respectively in the test set. The comprehensive recognition accuracy of the YOLOv4 model outperforms the other YOLO models. And the detection speed of the YOLOv4 model for pavement data video is 38.1 frames per second. Additionally, all the features of patches in the partial testing pavement images, no matter whether they are strip, block, intersection, blurry within the shadow, or background noise, can be correctly predictedby the rectangular box. The average localisation errors of the width and height of the predicted patches are 21 and 16 mm respectively, and the average IoU is 0.83. [ABSTRACT FROM AUTHOR]

Using solid waste to produce artificial aggregate (AA) to replace natural aggregate has attracted extensive research interest. This study proposes pressure granulation under minor water to produce AA. The strength formation and water-pressure synergy mechanisms are discussed by setting water and load configurations and characterizing the internal pore structure. In addition, the water damage to the AA is discussed. The results show that the squeeze-out effect caused by the synergistic effect of water and load determines AA's physical and mechanical properties. Furthermore, the law of the squeeze-out effect is proven by the fact that the AA with a compressive strength of 19.77 MPa was obtained under a 10% water-to-powder ratio and a 55 kN load. In addition, water erosion severely affects AA's strength, which might be relieved by decreasing the water absorption of AA. [ABSTRACT FROM AUTHOR]

• Proposed a simple and un-fluorinated superhydrophobic modification method for CNTs. • A modified CNTs/ epoxy coating with water contact angle of 151° was prepared on concrete surface. • The coating temperature rapidly increased from −10 ℃ to 81 ℃ under one sunlight intensity. • The freezing time of water droplets on the concrete surface had been extended from 55 s to 680 s. The problem of easy icing and difficult anti-icing on concrete pavement has prompted using superhydrophobic coatings as a potential solution. However, the coatings are prone to wetting failure after repeated icing-deicing cycles. In this study, a superhydrophobic and photothermal coating consisting of unfluorinated modified-carbon nanotubes (M-CNTs) and commercial epoxy is constructed by a simple spray process on concrete for anti-icing. Incorporating M-CNTs imparts the coating with exceptional superhydrophobic and photothermal characteristics, endowing the coating surface with excellent deicing under sunlight irradiation. The contact angle of the coating reaches 151° at −10 °C, and the freezing time extends from 55 s to 680 s. Under one sunlight intensity, the coating temperature rapidly increases from −10 ℃ to 81 ℃, and the ice changes from solid to liquid. It effectively acts as a barrier between water and the concrete surface, making it highly suitable and valuable in practical applications. [ABSTRACT FROM AUTHOR]

Since the correlation between the meso-structure composition and force chain transmission of asphalt mixtures, it has a significant impact on the evaluation and utilization of their material properties. Based on the discrete element method, this paper studied the internal force chains transmission mechanism of asphalt mixture under indirect tensile mode, and quantitatively analyzed the composition and distribution of the force chains. An aggregate template library for asphalt mixture was constructed using image segmentation and clump generation algorithm. Indirect tensile simulation was achieved by assigning relevant parameters, indicating a good correlation with laboratory tests. The tensile and compressive chain fields inside asphalt mixtures were visualized and characterized. The concept of strong and weak force chains was proposed, and statistical methods was used to analyze the strength, distribution, and evolution of force chains. The force transfer mechanisms of different components of asphalt mixtures have been elucidated, providing a research tool for their structural design and performance evaluation. • The aggregate template library was constructed within PFC3D. • Virtual indirect tensile test was built to analyze mechanical property. • The probability and distribution of the force chains were proposed. • The evolution law of the force chains was clarified. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel asphalt fume suppressant oil-absorbing organogel polystyrene-stearyl methacrylate (P(S-SMA)) was synthesized. • P(S-SMA) can absorb the lighter components of asphalt binder. • Adding P(S-SMA) can improve the rheological properties and reduce the fume particles and VOCs release of asphalt binder. • The interaction between the P(S-SMA) and asphalt components caused the above advantages. Hazardous fumes can be generated during the high-temperature construction of asphalt pavement. Various fume suppressants have been developed, but many may compromise the performance of asphalt binder, which shortens the service life of asphalt pavement. This study aims to investigate the performance of a novel fume suppressant, namely oil-absorbing organogel polystyrene-stearyl methacrylate (P(S-SMA)), which can reduce the construction fumes of asphalt binder while maintaining good rheological performance. The results of the Fourier Transform Infrared Spectroscopy (FT-IR), Fluorescence Microscopy (FM) and asphalt fume mass tests showed that adding P(S-SMA) can improve the aging resistance of asphalt binder and reduce the particles (≥1 μm) and volatile organic compounds (VOCs) released up to 19.6 % and 30.4 % within 1 h, respectively. The rheological test results indicated that P(S-SMA) could effectively improve the viscoelastic properties, high-temperature performance and fatigue resistance of asphalt binder due to the combination of "supporting" and "hardening" effects after adding P(S-SMA). With 5% P(S-SMA) added, elastic and viscosity properties were increased by 90.6 % and 25.3 % and fatigue life was increased by 38.9 % and 26.4 % at the strain levels of 2.5% and 5%, respectively. This study proved the feasibility of using P(S-SMA) as a novel performance-enhancing fume suppressant of asphalt binder. [ABSTRACT FROM AUTHOR]

The property of asphalt mastics consisting of asphalt binder and mineral fillers significantly affects the performance of asphalt mixture and also results in several forms of distresses in pavements. In addition to the materials properties, the interfacial interaction between asphalt binder and mineral fillers has a significant impact on the performance of asphalt mastics. This research aims to study the influence factors of interaction between asphalt binder and mineral fillers, and explore its relationship to viscoelasticity of asphalt mastics. Two kinds of asphalt binders, four kinds of mineral fillers and five filler/asphalt ratios were selected to prepare forty asphalt mastic samples. The interaction degree between asphalt binder and mineral fillers was characterised by a new introduced parameter C. The influence factors including the properties of asphalt and fillers were analysed. The correlations between interaction and mastics' rheological properties at different temperatures were statistically investigated. Results show that increasing the polar components ratio of asphalt binder, raising the specific surface area of fillers, making the size composition of fillers finer or increasing temperature all can increase the interaction degree between asphalt binder and mineral fillers. Linear relationship was considered to be an optimum type to represent the correlation between interaction degree and viscoelastic properties of asphalt mastic at temperatures between 15°C and 65°C. There was a very significant correlation between dynamic shear modulus/rutting factor/fatigue factor and C value when the temperature was between 25°C and 45°C. This kind of correlation weakened at 15°C and 55°C, but still significant. The phase angle of asphalt mastic has a significant correlation with interaction parameter C value only at 25°C and 35°C. [ABSTRACT FROM AUTHOR]

There is no method for evaluating the shear-fatigue resistance of sealants installed in the supporting layer of ballastless track, and the degradation mechanism of sealants under shear-fatigue loading has not been studied systemically. This study develops a shear-fatigue loading test method, and the adhesive properties of sealants are researched during shear-fatigue loading. The functional-group character at the failure interface is analyzed using infrared spectroscopy, and then the correlation between macromechanical behavior and the micromechanism is discussed. Results show that both maximum loads and failure displacements have a downward fluctuating trend during shear-fatigue loading, and sealants with lower hard-phase content present better shear-fatigue resistance. No new chemical bond forms in sealants, but more soft phases fuse into hard phases, which decreases the microphase separation degree of sealants. The developing rules for the hydrogen bonding index identify a trend similar to that of the mechanical behavior of sealants caused by the orientation of amorphous phases. The hydrogen bonding index degradation of higher R value sealants is deemed more significant, which agrees well with the results of the direct tension test. [ABSTRACT FROM AUTHOR]

This study fully intends to elucidate the mechanism of waste wood oil (WWO) modifier content on the microscopic action of bio-asphalt by utilising molecular dynamics simulations. Molecular models of virgin asphalt and its components, WWO modifier, and bio-asphalt with different WWO contents were created and verified by the fluctuation parameters, radial distribution function (RDF), and thermodynamics parameters. In addition, the influence of WWO content on thermodynamic and structural properties of bio-asphalt and interactions between components was quantitatively evaluated through Hansen solubility parameter, intermolecular interaction energy, mean square displacement, RDF, and fraction of free volume. The simulation findings show that the compatibility of bio-asphalt is associated with the composition of the asphalt molecule and the compatibility ranking is not affected by the WWO content. In addition, the WWO modifier is most compatible with the resin and least with the saturate. The interaction energy between virgin asphalt and WWO and the particle migration in the asphalt models increases with increasing WWO content. Furthermore, the introduction of WWO increases the first RDF peak intensity of each asphalt component. An increase in WWO content does not change its own chemical composition. Moreover, the free volume of the system decreased as the WWO was added. [ABSTRACT FROM AUTHOR]

• The optimum preparation technology of CF-GT conductive asphalt mixture with low resistivity are clarified. • The resistance and stress of the mixture have an excellent linear correlation in NPC stage. • The feasibility of applying graphite tailings to prepare the conductive asphalt mixture is demonstrated. The massive accumulation of graphite tailings (GT) brings huge pressure to environmental engineers. Meanwhile, the conductive asphalt pavement industry is suffering from the high construction cost and the complex acquisition of conductive materials. The application of GT in asphalt mixture as a conductive material may be a win–win solution for the above concerns. This study aims to evaluate the feasibility of preparing carbon fiber graphite tailings (CF-GT) conductive asphalt mixture. The optimum preparation technology and material ratio were explored. The service performance tests of the conductive asphalt mixture were conducted, including conductive characteristics, electrothermal performance and pavement performance. Based on the experimental results, 0.3% (mass fraction) 6 mm-polyacrylonitrile (PAN)-based carbon fiber (CF) and 12% (mass fraction) GT were selected as conductive materials to prepare conductive asphalt mixture with resistivity of 5.75 Ω∙m. The addition of GT reduced the resistance by a maximum of 59.8%. The temperature-sensitive and pressure-sensitive characteristics of the mixture have staged characteristics. Moreover, the resistance and stress of the mixture have an excellent linear correlation in the positive pressure coefficient (PPC) effect stage and negative pressure coefficient (NPC) effect stage respectively, especially NPC. Conductive asphalt mixture has a good heating effect after being powered on. GT combined with CF enhanced the high-&low-temperature performance but deteriorated the moisture damage resistance performance of the asphalt mixture. The feasibility of CF-GT conductive asphalt mixture was demonstrated. [ABSTRACT FROM AUTHOR]

Individual effect of aging and rejuvenator recycling on basic properties of asphalt is readily recognized, but there is only limited understanding about whether the recycling of SBS- (styrene-butadiene-styrene-) modified asphalt is an inverse process of aging or not. To compare the effects of aging and rejuvenator on microproperties and molecular composition of SBS-modified asphalt, comprehensive performance tests and physical-chemistry experiments were conducted. The results of infrared spectroscopy tests demonstrate that the reticular crosslinking structure of asphalt was destroyed and SBS's modification effect was gradually lost after aging. This can cause the strengthening of high-temperature performance and reduction of the low-temperature anticrack property of SBS-modified asphalt. Scanning electron microscope shows that the island structure of SBS-modified asphalt disappeared after aging. Energy spectrum analysis shows that the C (carbon) content of aged SBS-modified asphalt has decreased, while the O (oxygen) content and S (sulfur) content have increased obviously. Results of the fluorescence microscope, SEM, and rheological tests show that the epoxy functional group compounds of aliphatic glycidyl ether resin had high reactivity; the triblock molecular structure of SBS and the mechanical performance of SBS-modified asphalt were recovered. [ABSTRACT FROM AUTHOR]

• Perform fractal and multifractal analysis on the asphalt mixture's aggregate skeleton and void structure. • The influence of design and construction indicators on the microstructural features of pavement materials. • The fractal/multifractal parameters' physical sense and role in characterizing the 3D microstructure are clear. The aggregate skeleton and void structure in the asphalt mixture are critical and highly correlated to the mechanical performance of the pavement. However, the extreme heterogeneity and complexity bring devastating difficulties to characterizing and analyzing the mixtures' mesostructure. Therefore, this study aimed to propose a novel depicting scheme accounting for the size distribution and spatial arrangement of the mixtures' components utilizing the fractal and multifractal analysis. Two compaction methods (Marshell and Superpave) and three design indexes (gradation, NMAS, and compaction work) were adjusted to prepare the samples, which were then scanned and digitally reconstructed. The fractal dimension (D) and related multifractal indicators (i.e., Δ α and Δ f (α)) were determined and applied to quantitative assess the structural changes. Finally, the relationships of design indexes to fractal and multifractal behaviors were comprehensively discussed. Results indicate that fractal and multifractal theories are feasible in describing the heterogeneous particle skeleton and void structure in the asphalt mixture. Firstly, the multifractal approach was proven to allow a more informative characterization of 3D systems than simple fractal theory. Moreover, the excellent correlation between the design/construction and fractal/multifractal indicators has been confirmed for asphalt pavement. Overall, the fractal and multifractal indicators enriched the options for microstructural evaluation, which will be conducive to revealing the relationship between the microstructural characteristics and mechanical performance of the asphalt mixture. [ABSTRACT FROM AUTHOR]

The British pendulum tester (BPT) provides a method to measure the skid resistance of pavement, which possesses both theoretical and practical engineering significance. This article aims to establish a numerical hysteresis friction model for BPT to reproduce the dynamic motion of the slider and estimate the pavement friction based on surface texture roughness, rubber viscoelasticity property and contact characteristics. The analytical hysteresis friction model was introduced based on one of the modern rubber friction theories. As an input parameter of this model, the average penetration depth of rubber was calculated based on the interfacial separation assumption. A numerical model was established by combining the geometric and motion characteristics of BPT. To validate the model, the self-affine characteristics of texture from four types of asphalt pavement were analysed; simultaneously, the storage and the loss modulus of rubber slider at various frequencies were obtained using the Zener constitutive model. As a result, the velocity of the slider decreases gradually with the dynamic fluctuation of the friction coefficient. A significant linear correlation was found between the predicted values and the measured data. This numerical friction model performs some potential for friction estimation. However, more conditions need considering for the improvement and practicability of the model. [ABSTRACT FROM AUTHOR]

Asphalt pavements are continuously subjected to cyclic temperature variations induced by varying day–night and seasonal temperatures. However, the effect of thermal cycling on asphalt materials has not been thoroughly documented. This study conducted accelerated thermal cycling tests on asphalt mastics to simulate the environmental temperature variation. The evolution of the rheological properties and phase behaviors under cyclic temperature variations was clarified. The temperature factors sensitive to damage were identified by establishing the quantitative relationship between the cyclic temperature parameters and these properties. Results demonstrated that, as the expansion of cyclic temperature ranges, the three asphalt mastics gradually lost their viscosity properties and became increasingly elastic. Thermal cycling increased the stiffness and high temperature deformation resistance of the three asphalt mastics, but significantly reduced their stress relaxation capability. The phase structures were degraded upon thermal cycling, weakening the asphalt-aggregate interaction. The temperature difference and cyclic high temperature were the primary factors affecting the rheological performance of the asphalt mastics. SBS modified asphalt mastic displayed remarkable resistance to thermal cycling, demonstrating its potential for application in regions with frequent temperature fluctuations. This research can help us understand the evolution of asphalt pavement performance in areas with frequent temperature changes at a macro-level. [ABSTRACT FROM AUTHOR]

Improving the anti-ageing performance of bitumen plays a vital role in prolonging the service life of bituminous pavement. A bituminous additive for resisting all-weather ageing (BARAA), with excellent anti-ageing performance and fewer side effects, was developed in this study. The service life of bitumen can be doubled by using BARAA. The results show that the anti-ageing index and influence index can quantitatively evaluate the anti-ageing performance of anti-ageing additives. The BARAA was composed of amine antioxidant (1.89% by weight of base bitumen), Ni-containing antioxidant (3%) and hindered amine light stabilisers (0.7%). BARAA effectively delayed the deterioration of bitumen performance during ageing. The Jnr reduction of BARAA-modified bitumen caused by ageing was 17.7% of the base bitumen. At −12°C and −18°C, the S increase of BARAA-modified bitumen caused by ageing was about 35% of the base bitumen. The oxidation during ageing was inhibited. The growth of sulphoxide groups can be curbed by BARAA. After long-term ageng, the aromatic ring increase of BARAA-modified bitumen was 41.1% of the base bitumen. In addition, the increase of average molecular weight and functional group index of BARAA-modified bitumen caused by long-term ageing was 57% and 19.1% of the base bitumen, respectively. [ABSTRACT FROM AUTHOR]

Asphalt pavements are continuously subjected to cyclic temperature variations induced by varying day–night and seasonal temperatures. However, the effect of thermal cycling on asphalt materials has not been thoroughly documented. This study conducted accelerated thermal cycling tests on asphalt mastics to simulate the environmental temperature variation. The evolution of the rheological properties and phase behaviors under cyclic temperature variations was clarified. The temperature factors sensitive to damage were identified by establishing the quantitative relationship between the cyclic temperature parameters and these properties. Results demonstrated that, as the expansion of cyclic temperature ranges, the three asphalt mastics gradually lost their viscosity properties and became increasingly elastic. Thermal cycling increased the stiffness and high temperature deformation resistance of the three asphalt mastics, but significantly reduced their stress relaxation capability. The phase structures were degraded upon thermal cycling, weakening the asphalt-aggregate interaction. The temperature difference and cyclic high temperature were the primary factors affecting the rheological performance of the asphalt mastics. SBS modified asphalt mastic displayed remarkable resistance to thermal cycling, demonstrating its potential for application in regions with frequent temperature fluctuations. This research can help us understand the evolution of asphalt pavement performance in areas with frequent temperature changes at a macro-level. [ABSTRACT FROM AUTHOR]

Improving the anti-ageing performance of bitumen plays a vital role in prolonging the service life of bituminous pavement. A bituminous additive for resisting all-weather ageing (BARAA), with excellent anti-ageing performance and fewer side effects, was developed in this study. The service life of bitumen can be doubled by using BARAA. The results show that the anti-ageing index and influence index can quantitatively evaluate the anti-ageing performance of anti-ageing additives. The BARAA was composed of amine antioxidant (1.89% by weight of base bitumen), Ni-containing antioxidant (3%) and hindered amine light stabilisers (0.7%). BARAA effectively delayed the deterioration of bitumen performance during ageing. The Jnr reduction of BARAA-modified bitumen caused by ageing was 17.7% of the base bitumen. At −12°C and −18°C, the S increase of BARAA-modified bitumen caused by ageing was about 35% of the base bitumen. The oxidation during ageing was inhibited. The growth of sulphoxide groups can be curbed by BARAA. After long-term ageng, the aromatic ring increase of BARAA-modified bitumen was 41.1% of the base bitumen. In addition, the increase of average molecular weight and functional group index of BARAA-modified bitumen caused by long-term ageing was 57% and 19.1% of the base bitumen, respectively. [ABSTRACT FROM AUTHOR]

Hydronic pavement heating systems are environmentally friendly, clean, and sustainable alternatives to chemical salt for eliminating ice/snow that has accumulated on pavement surfaces and to improve driving safety during days with frost and snowfall. The first task in designing a hydronic pavement heating system is determining heating capacity. A simulation method for the heat-mass coupled snow melting process is described. This numerical algorithm can predict system heat consumption, surface condition, and pavement temperature at a specific depth when inlet fluid temperature and meteorological data are provided. The model is validated experimentally and included in the discussion of design alternatives to hydronic pavement heating systems. Simulation test results show the importance of preheating time, heating capacity, weather condition, and snow melting target in snow melting performance. It is reasonable to design hydronic pavement heating systems under consideration of specific climate conditions and snow melting target. Finally, the design alternatives for 12 representative cities in China with various snow melting targets have been proposed based on the collected statistics of limit snowfall conditions from the last 30 years. Compared with the heat-only model, the utilization of the heat-mass coupled snow melting model can avoid overestimating the required heat fluxes to achieve a specific snow melting performance. [ABSTRACT FROM AUTHOR]

The low-temperature performance of an asphalt mixture plays important roles in the thermal cracking mechanism of asphalt pavements in cold regions. However, the existing asphalt mixture design process does not involve a design parameter for low temperature performance as the asphalt content is determined. In this study, two types of asphalt mixtures are involved, Asphalt Concrete (AC) and Stone Mastic Asphalt (SMA), which are the most widely used materials for surface layer. The zone for low-temperature performance was defined on the basis of a survey of pavement distresses and numerical analysis. The design parameter was captured from an indirect tensile test by using Digital Image Correlation (DIC) analysis, considering the universalizability and simplification of the indirect tensile test. The selected indicators, such as tensile failure strain, validated that significant linear correlations existed between bending beam test and thermal stress restrained specimens test. Thus, the design parameter, which was defined as the tensile failure strain ( ε DIC ), could characterize low-temperature property with asphalt content. Moreover, the critical strain of ε DIC was proposed. The low-temperature design parameter ( ε DIC ) was applied to the Marshall design method. The optimum asphalt content based on the new design method was slightly greater than that of the conventional Marshall design method. The evaluation methods used in this paper indicate that the low-temperature property of the asphalt mixture created by the new design method was better. [ABSTRACT FROM AUTHOR]

The low-temperature performance of an asphalt mixture plays important roles in the thermal cracking mechanism of asphalt pavements in cold regions. However, the existing asphalt mixture design process does not involve a design parameter for low temperature performance as the asphalt content is determined. In this study, two types of asphalt mixtures are involved, Asphalt Concrete (AC) and Stone Mastic Asphalt (SMA), which are the most widely used materials for surface layer. The zone for low-temperature performance was defined on the basis of a survey of pavement distresses and numerical analysis. The design parameter was captured from an indirect tensile test by using Digital Image Correlation (DIC) analysis, considering the universalizability and simplification of the indirect tensile test. The selected indicators, such as tensile failure strain, validated that significant linear correlations existed between bending beam test and thermal stress restrained specimens test. Thus, the design parameter, which was defined as the tensile failure strain ( ε DIC ), could characterize low-temperature property with asphalt content. Moreover, the critical strain of ε DIC was proposed. The low-temperature design parameter ( ε DIC ) was applied to the Marshall design method. The optimum asphalt content based on the new design method was slightly greater than that of the conventional Marshall design method. The evaluation methods used in this paper indicate that the low-temperature property of the asphalt mixture created by the new design method was better. [ABSTRACT FROM AUTHOR]

The interfacial behavior between asphalt binder and mineral fillers directly effects the performance of asphalt mastics or asphalt mixture. However, the understanding about the interfacial interaction between these components is very limited, although the role of individual ingredients on its performance is readily recognized. In order to study the interactions between asphalt binder and mineral fillers, it is necessary to propose an effective evaluation indicator. In this research, dynamic mechanical analysis (DMA) was used to obtain the viscoelastic parameters of different asphalt binder and asphalt mastics. The interfacial interaction parameters between asphalt binder and fillers were calculated based on the viscoelastic parameters and relevant theoretical models. The interaction parameters were compared and the calculated methods were improved. The results show that compared to interfacial interaction parameters Luis Ibrarra- A and K. Ziegel- B , C value based on Palierne theoretical model had the least sensitivity to the volume fraction of fillers. The checking of fitting goodness of improved interaction parameter C value shows a high determination coefficient. It demonstrates that the C value can effectively evaluate the interfacial interaction. The interfacial interaction becomes stronger with the temperature increasing. The higher the specific surface area of filler, he stronger the interfacial interaction between it and asphalt binder. [ABSTRACT FROM AUTHOR]

For digitizing the granular material systems, including asphalt mixture, the sieving size of the particles plays an irreplaceable role. However, the traditional methods based on equivalent conversion performed terribly in measuring the size of individual particles. This study combined digital image processing, ensemble learning, and over-sampling algorithms to develop a novel sieving method. Besides, the comprehensive importance ranking of variables was put forward to assist in optimizing the random forest. The results show that the data collection method proposed in this study can quickly gain bulks of digital aggregates without a complicated reconstruction process. The synthetic minority over-sampling algorithm was conducive to the accuracy ascension by balancing the database. By scoring variables' relative importance and function, the variable selection method can effectively reduce system complexity, thus improving computational efficiency and robustness. Based on the above-improving processes, the measuring precision of the aggregates' sieving opening was raised by over 20%. [Display omitted] • The predictive accuracy for the sieving technique of irregular particles is improved. • The balance method of the aggregate database is proposed for accuracy ascension. • The dimensionality curse is overcome by filtering variables in advance. [ABSTRACT FROM AUTHOR]

• Emphasize the impact of meso-structural variability and uncertainty of HMA. • Provide a system for evaluating and analyzing the meso-structural skeleton. • Clarify the relationship between the IC particles and the DASR-based skeleton. The variability and uncertainty bring great trouble to the application and in-depth research of asphalt mixture. This study aimed to detect the microstructural differences between the asphalt specimens after fixing the experimental and environmental inputs. To this end, the digital image correlation (DIC) method was utilized to propose reliable skeletal and disruptive meso-parameters. Besides, the close packing theory and digital sieving technique were combined to classify the internal particles of the mixture structure. Afterward, the stochastic behaviors of the particle systems containing the dominant aggregate size range (DASR) and interstitial component (IC) aggregates were thoroughly discussed. Finally, the disruption effect of IC on the skeletal structure was also investigated. The analysis results show that the microstructure of the asphalt mixture was a typical random system with a great deal of contingency. The aggregate contact index (ACI) was the most variable among the overall skeletal parameters, with a variation coefficient (COV) of 13.24 %. Besides, almost all the microstructural indexes indicated that about 4% of the specimens in parallel tests showed significant variability behavior, e.g., N a ,13.2 > N a ,16.0. Besides, the microstructural uncertainty of the minority class, e.g., the 16-mm aggregates with a 4% ∼7% COV higher than the other classes, was particularly significant. Finally, the interference effect was proven to focus on the contact behavior of DASR particles, thus damaging the DASR-based system. This study not only emphasizes the impact of variability but provides implications for controlling the performance of asphalt pavement. [ABSTRACT FROM AUTHOR]

In this study, we investigate the spatial distributions of the internal structures in semirigid base materials (SRBMs) and explore their effect on the service performance of the SRBMs. X-ray computed tomography (X-ray CT) was used to conduct a spatial voids structure analysis. Three variates were selected to study the factors influencing the spatial distributions of the internal structures, including freeze-thaw cycles, curing time, and cement content. The results show that, with the increase in the number of freezing and thawing cycles, the average porosity, void area, and void number of the SRBM samples increased, and the average void diameters of all samples initially increased and then decreased. These trends led to an increase in the mass loss ratio and strength loss ratio. Increasing the cement content and extending the curing time decreased the average number of voids, average void area, and average void diameter and decreased the mass loss ratio and strength loss ratio of the SRBMs. The top and bottom of the SRBM samples were more porous than the middle of the samples, whereas the maximum value of the average void diameter was observed in the middle of the samples. [ABSTRACT FROM AUTHOR]

Failure behavior of asphalt mixture is the process of local deformation accumulation, therefore, local deformation investigation is the base work of failure behavior. Digital image correlation (DIC) method is an optical method which can calculate the local deformation in the failure process. This paper aims to evaluate the precision, select the optimal test parameters for DIC deformation measurement based on natural speckle image, and investigate the local deformation characteristic in the failure process for different mixtures. The results show the image quality of AC with smaller normal maximum aggregate size (NMAS) is better for DIC deformation calculation, the relative deviation of virtual translation and shear test can satisfy the precision requirement, the optimal subset size is 31. Based on the strain distribution, the optimal local deformation measure length for indirect tensile test is set as 50 mm, the critical steady strain is proposed based on R 2 obtained by the least squares fitting method, according to local deformation characteristic, the results show SMA can bear more deformation before unstable deformation stage and failure. [ABSTRACT FROM AUTHOR]

• The periodic perturbation method is adopted to calculate the ZSV of asphalt binder MD models. • Asphaltene and saturates more easily reorient their conformation in shear flow. • Short, unordered planar accumulations structures dominate asphalt binder microstructure. This study aims to develop molecular model of asphalt binder and investigate the reasonable simulation scale of molecular dynamics (MD) in researching the viscosity property and microstructure of asphalt binder. Eighteen MD models with atom numbers in the range of 10,000–750,000 for the three typical asphalt binder AAA-1, AAK-1, and AAM-1 in the Strategic Highway Research Program (SHRP) were constructed. Density, Zero Shear Viscosity (ZSV), and microstructure characters of the asphalt binders were analyzed by MD to compare with experiment data. The result shows that densities and the ZSV values of the MD models are all close to the experimental values. These models with atom numbers of 130,000–375,000 are well stabilized and have lower errors, which is recommended to research the density and viscosity properties. In the shearing process, the shear flow induces the conformational transitions of the asphalt binder, and most molecules tend to parallel the shear direction. Asphaltenes and saturates components are easier to reorient their conformation in shear flow. Through the density map obtained by MD simulation and the asphaltenes image from the High-resolution transmission electron microscopy in literature, we speculate that short and unordered planar accumulations structures dominate the asphalt binder microstructure, which is a further explanation of the colloidal theory. [ABSTRACT FROM AUTHOR]

• Investigated the effects of damage and thixotropy on viscoelastic parameters; • Obtained a linear relationship between G ∗ E and θ under the influence of thixotropy; • Developed a thixotropy model to characterize the change of G ∗ E under the influence of thixotropy; • Calculated damaged density separating the influence of thixotropy. Accurate characterization of the fatigue resistance of asphalt binder is of great significance to the prediction of asphalt pavement performance. Traditionally, apparent changes in viscoelastic parameters, including dynamic shear modulus and phase angle, with the number of loading cycles are used to define the fatigue performance of the asphalt binder. However, thixotropy also leads to changes in these viscoelastic parameters, and its contribution is not yet well understood. This study develops a method to quantify the effects of damage and thixotropy on the changes of viscoelastic parameters under the cyclic stress-controlled loading mode. The new method includes the four key steps: (1) determining the thixotropy influence-dominated phase; (2) establishing a thixotropy model to characterize the influence of thixotropy on the effective dynamic shear modulus; (3) calculating damage density from the apparent and effective dynamic shear moduli; and (4) characterizing thixotropy behavior based on Black space diagram. The effectiveness of the newly developed method is verified by the time sweep test, which is conducted on two types of asphalt binder under varying stress levels.with a loading frequency of 10 Hz and a test temperature of 25 °C. The results show that: (1) the change of dynamic shear modulus is resulted from the damage and thixotropy, while that of phase angle is only caused by the thixotropy; (2) thixotropy leads to the decrease of dynamic shear modulus and increase of phase angle; and its influence on viscoelastic parameters increases with the loading time and stress level increased; (3) under the influence of thixotropy, the dynamic shear modulus is linearly related to the phase angle, which is independent of the stress level applied and the damage accumulated in the asphalt binder. [ABSTRACT FROM AUTHOR]

• The voxel-based morphological process optimized the automatic extraction procedure of digital aggregates. • A robustness and accuracy analysis map was designed based on the virtual gradation of asphalt mixture. • The three-dimensional reconstruction algorithm can be evaluated quantitatively and then optimized purposefully. • Four types of internal defects generated by the traditional pixel-based method were detected. Three-dimensional image reconstruction plays a pivotal role in microstructure information extraction and virtual mechanical experiments of asphalt mixture. However, the traditional pixel-based reconstruction algorithm tends to be powerless in processing three-dimensional (3-D) mesostructure. Therefore, this paper aims to develop a robust and accurate algorithm for high-quality aggregate particle extraction. To this end, the global thresholding and three-dimensional mathematical morphological methods were conducted directly based on voxel operation. Then the calculated weight-based gradation was utilized to develop the robustness and accuracy analysis map (RAAM), which assesses and compares the traditional and novel reconstruction algorithms. As a sequence, the voxel-based method had higher accuracy and lower perturbation sensitivity than the existing procedures. Additionally, the computed efficiency was improved dramatically by breaking tight bounds and conservatism. Finally, the inevitable algorithm defects caused by multiple morphological treatments in the traditional method have disappeared in the novel one. [ABSTRACT FROM AUTHOR]

[Display omitted] • The relationships among phase behavior, aging mechanism and modification effect were established. • Different aging rate exist with the raising aging time. • The aging process can be divided into three regions according to modification effect and phase behavior. • It is suggested that the parameter of toughness curve can be used as one of the critical indicators of modification effect. Aging behavior has always been a key issue in the asphalt industry, and the undetermined extent of the residual modification effect in aged SBS-modified asphalt can lead to uncertain performance. The relationship between the modification effect and aging mechanism has not been well examined, which leads to whether aged asphalt can be regarded as modified asphalt or conventional asphalt. To overcome this issue, this paper conducted fluorescence microscopy tests, dynamic shear rheometer tests, multiple stress creep recovery tests and toughness and tenacity tests on aged SBS-modified asphalt. Five quantization parameters were proposed to determine the phase structure and modified effect. Multinomial logistic regression analysis was performed to categorize the phase structure with increasing aging time. Based on the results, it was found that the aging process can be divided into three regions according to the modification effect. The first region presented a slower aging rate, and copolymer relaxation appeared, but chemical crosslinking still existed during this period. Aging dominated the second region, in which copolymers dissolved out and the polymer network was destroyed, and the quantization parameters sharply changed, eventually, the network structure was completely destroyed in the third region. The failure of the modification effect is also determined by evaluating the toughness curve. It is reasonable to assume that there is no difference between SBS-modified asphalt and conventional asphalt after RTFOT 6 h in terms of toughness curve. It is suggested that the toughness curve parameter can be used as one of the critical indicators to determine whether aging asphalt can be regarded as modified asphalt or conventional asphalt. [ABSTRACT FROM AUTHOR]

The service performances of asphalt pavement, especially rutting, will be inevitably affected by climate change. However, existing studies have generally focused on the rutting depth and rutting life, and thus became insufficient for comprehensively evaluating the influence of climate change on rutting over the service life. A resilience assessment method for asphalt pavement rutting is developed to solve the above problem. First, the original resilience method is extended to fit the system whose performance level continues to decline. Then, the calculation formulas of rutting resilience are derived by combining the rutting prediction model and the level assessment model. Subsequently, the influence degrees of climate change in representative cities on rutting resilience are studied. The results suggest that neglecting climate change in rutting design of asphalt pavement will lead to insufficient resilience, especially in northern China. Furthermore, the predicted temperature under RCP8.5 should be employed for asphalt pavement design. [ABSTRACT FROM AUTHOR]

The workability of grouting cement asphalt emulsion (CA) mortar is governed by the intrinsic thixotropic behavior of CA paste, but limited information is reported about the thixotropic behavior of CA paste. A new thixotropy method of constant shear rate test is proposed to study the thixotropic behavior of CA paste with different asphalt emulsion to cement ratios (AE/C). In the model, the initial structure parameter and the structure rebuilding rate are used to quantitatively describe the structure rebuilding process, the characteristic time of de-flocculation is used to evaluate the de-flocculation process, and the equilibrium shear stress is used to study the irreversible change of CA paste in the thixotropy test. Results show that CA pastes have significantly different thixotropic behavior compared to cement paste. The initial structure parameter and structure rebuilding rate of CA pastes are much smaller than cement paste, and the structure rebuilding rate decreases significantly with AE/C. The characteristic time of de-flocculation of cement paste changes little at different resting time, however, it increases significantly at the first 5 min resting time and then keep stable for CA pastes. The equilibrium shear stress of cement paste does not change in 20 min, but it increases with time for CA pastes due to the demulsification of asphalt emulsion. [ABSTRACT FROM AUTHOR]

A combination of advances both with respect to experimental techniques as well as image processing procedures accurately describes moisture distribution in the internal structure of asphalt mixtures using X-ray computed tomography technology. The quantitative and qualitative X-ray CT results for partially saturated asphalt mixtures are displayed, which is obtained with different test parameters of X-ray CT and sample sizes to demonstrate the effect of these parameters on measurement accuracy of the hydraulics of asphalt mixtures using X-ray CT images, considering the aspects of both image resolution and contrast. In addition, we present several applications of our two-dimensional X-ray CT images before and after saturation, which analyzes the moisture distribution in the micro-scale of asphalt mixtures with various loading sizes and speed. This method provides an effective opportunity to reveal the dynamic/static water distribution characteristics on the micro-scale of asphalt mixtures and verify various numerical modeling methods. [ABSTRACT FROM AUTHOR]

Particle motion is the critical factor leading to the internal deformation of granular materials. However, relying on conventional techniques to monitor particle motion in internal deformation of granular materials has limitations. This study presents a novel method to monitor the internal movement of granular materials using intelligent aggregate. The intelligent aggregate packaging structure is fabricated through industrial CT technology and 3D printing. The six position method and fast fourier transform method are used to eliminate the measurement error caused by the packaging structure and the rutting tester vibration noise respectively. The results show that intelligent aggregate could maintain good linkage with surrounding aggregates under load, and the fine aggregates have a greater impact on the stability of the coarse aggregate skeleton. This method based on intelligent aggregates provides a basic technology for further real-time monitoring of granular material properties. • An intelligent aggregate is developed using industrial CT and 3D printing. • A method is adopted to improve intelligent aggregate acceleration accuracy. • Rutting instrument vibration noise is eliminated using fast fourier transform. • An method is proposed to evaluate internal deformation of granular material. • The method perform excellently in monitor of aggregates skeleton deformation. [ABSTRACT FROM AUTHOR]

The rheology of fresh CA pastes of different asphalt emulsion to cement mass ratio (AE/C) with different particle volume fraction was studied. A modified Herschel–Bulkley model was proposed to fit the flow curve of CA pastes and calculate the yield stress and special viscosity (minimum apparent viscosity) of CA pastes. According to the fitted viscosities and yield stresses, a viscosity model was employed to establish the relationship between viscosity and particle volume fraction of CA pastes, and a yield stress model was employed to study the relationship between yield stress and particle volume fraction of CA pastes. Based on the two relations, maximum particle packing density of CA pastes was calculated and the relation between yield stress and viscosity was established to study the rheology of grouting CA pastes. Results indicate CA pastes with different AE/C have significant different relation of viscosity with particle volume fraction and relation of yield stress with particle volume fraction. In the condition of the same viscosity, the yield stress of CA pastes decreases quickly with the increasing AE/C from 0 to 0.4, and then increases slightly with AE/C from 0.4 to 1.0. The yield stress of CA pastes is very low and should be improved for grouting. These works can well reveal the rheology of CA pastes. [ABSTRACT FROM AUTHOR]

A heat and mass coupled model is developed for the pavement snow melting systems that utilize low-temperature heating fluids. This model is implemented in HVACSIM (heating ventilation air conditioning SIMulation) Plus and used to simulate the performance of hydronically heated pavement. The model is validated by tested data from medium-scale snow melting experiments performed at the Harbin Institute of Technology. Validated results suggest the significant improvement in simulating the performance of hydronically heated pavement by the inclusion in the model of mass transport process. Existing literature claims that the typical hydronic snow melting process consists of three sub-stages: the idling stage, the snow melting stage, and the after melting stage; this is adopted for the analysis of snow melting performance of the model, including its given heating capacity, equivalent snowfall rate, and weather conditions. Ambient temperature and heating load play a dominant role among the decision variables at the idling and after melting stages, while heating load and equivalent snowfall rate are the two major factors of snow melting performance at the snow melting stage. Based on the two main sources of impact for each sub-stage, the performance-energy consumption-environmental relation is quantitatively determined and the operation strategy for hydronically heated pavement is proposed to balance snow melting performance, environmental criteria, and energy consumption. [ABSTRACT FROM AUTHOR]

Highlights: [•] Long rest periods and few loading cycles result in improved healing. [•] The effect of terminal cases on healing is greater than the effect of rest periods. [•] We established a universal healing evaluation index for asphalt binder. [•] The healing ranking of binders suggested by HIm-c, HIem-c and HIvm-c are the same. [•] The healing ranking of the binders is the same as the ranking of the corresponding. [ABSTRACT FROM AUTHOR]

Highlights: [•] We determined best contents of raw materials of composite modified asphalt sealant. [•] Central composite design is effective in optimizing performance of composite modified asphalt sealant. [•] It is effective to use energy method to evaluate viscoelastic properties of asphalt. [•] We analyzed the effects of rubber powder, additive, SBS and SBR on rheological behavior of modified asphalt. [Copyright &y& Elsevier]

Highlights: [•] We studied phase behavior of asphalt mastic upon DMA, DSC and Brookfield viscometer. [•] The addition of fillers can increase Tg and glass transition activation energy. [•] The addition of fillers can improve the temperature sensitivity of asphalt mastic. [•] The addition of fillers can promote phase separation occur in modified asphalt. [•] Fillers have little impact on the discrete distribution of wax in asphalt. [Copyright &y& Elsevier]

Highlights: [•] Sessile drop method can characterize surface free energy of viscoelastic materials. [•] Column wicking technique can characterize surface free energy of solid powders. [•] Specific surface area effects interaction between asphalt and fillers remarkably. [•] The adhesion work can response the moisture sensitivity of asphalt mixtures. [•] A good correlation exists between complex modulus G ∗ and work of adhesion. [Copyright &y& Elsevier]

Highlights: [•] We study hardening mechanism of cement asphalt paste when fixing asphalt emulsion to cement ratio. [•] Type of emulsifier and its dosage both affect the hardening process of cement. [•] Significant differences in hydration parameters are detected utilizing different emulsifier. [•] Emulsifier with less retarding effect can develop a high early strength CA mortar. [Copyright &y& Elsevier]

[Display omitted] • The dipole moment was used to represent the molecular polarity and further divided the aromatics and resins molecules. • The HOMO-LUMO gap shows that resins and aromatics molecular are more stable than asphaltenes. • 1H-NMR, elements analysis, SARA components tests were used to solve asphalt the molecular ratio. To further develop the microscopic structure of asphalt, the new asphalt molecular model including 50 types of molecules was proposed. The dipole moment, molecular electrostatic potential, and HOMO-LUMO gap were calculated by quantum chemistry methods. Based on the polarity represented by dipole moment and molar mass, the molecules were further divided into the aromatics and resins molecules in theory. The result shows that the donor atoms are located in the benzene concentrated region are easily attacked by electrophiles. The accept atoms are located in saturated branched chains and cycloalkanes are easily attacked by nucleophiles. The HOMO-LUMO gap shows that the asphaltene molecular meets with the experiment results of the asphaltene optical gap. The resins and aromatics molecular own similar chemical stability, both of them are more stable than asphaltene. Finally, 1H-NMR, elements analysis, and SARA components experiments were connected with the molecular model we presented to solve the molecular ratio of fourteen kinds of asphalt. [ABSTRACT FROM AUTHOR]

• The uncertainty of permanent deformation process of asphalt mixture was analyzed. • The method to determine damage states for permanent deformation was proposed. • The characteristic points at strain rate curves complied with normal distribution. • The fragility curves for permanent deformation of asphalt mixture were established. This study aims to develop a fragility analysis methodology for asphalt mixture to assess the uncertainty of the permanent deformation development of asphalt mixture subjected to repeated load based on parallel tests. The methods to determine limit states and damage states for the permanent deformation process based on characteristic points at the strain rate curve were proposed. The distribution types of characteristic points were tested, and the corresponding probability distribution function was employed to plot fragility curves for limit states. According to the relationship between limit states and damage states, fragility curves for damage states were established subsequently. [ABSTRACT FROM AUTHOR]

Abstract: Asphalt binder has a critical effect on the performance of asphalt mixtures. Thus, asphalt binder is of great concern to pavement engineers and researchers. Usually, asphalt binder is studied in dynamic space and steady-state space separately, and the property indices are researched separately. As researchers delved deeper, they found that it is important to combine the dynamic properties and steady-state properties, especially for establishing rheological curves and constitutive equations. The Cox–Merz relationship can connect the properties in dynamic space to those in steady-state space. This relationship is widely used in polymer system and shows good results. This study focused on the applicability of the Cox–Merz relationship as it pertains to asphalt binder. The Cox–Merz relationship was applied to six neat asphalt binders. Then, the applicability of the Cox–Merz relationship for asphalt binder was studied and the criterion to verify whether the Cox–Merz relationship is followed or not was established. Finally the viscosity functions when the Cox–Merz relationship used were studied, and the Cross model and the Carreau model were compared. The results show that the Cox–Merz relationship is followed in the shear-thinning region and not always followed in the zero-shear-rate-limiting viscosity region, and it is useful when obtaining the viscosity function. [Copyright &y& Elsevier]

A hydronic snow melting pavement system is an efficient and sustainable snow removal approach. However, the conventional operation method remained unclear and usually led to a waste of energy. This study developed a thermal-economic model to assess this system's economic cost and snow melting effect. The multi-objective optimization (MOO) model and genetic algorithm (GA) were adopted to optimize the operation strategy, which includes fluid temperature (FT) and idling duration (ID). The accuracy of the MOO model was verified by a convergence study. The optimal results were organized in nomograms and implemented at Beijing Daxing International Airport. The results showed that the tournament selection method performs better in MOO solving. The optimal results indicated that it would obtain a better effect to balance the economic benefit and snow melting effect by adjusting FT than ID. And the MOO model can export the appropriate strategy in response to various snowfall conditions. Specifically, the optimal strategy implementation in the case study improved the snow-free duration ratio by 126% and saved the economic cost by 7% compared to the conventional strategies. The investigation provided an alternative operation strategy to minimize the energy cost for this system while ensuring the snow melting effect. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: The healing performance of asphalt binder has a critical impact on the fatigue performance of asphalt binders, mixture and pavement. Although studies of the healing characteristics of asphalt binder can be found in some references, the subject has not been researched thoroughly. No universal healing evaluation index currently exists, and the fatigue and healing processes are not fully understood. For this study, experiments were performed to characterize the healing characteristics of four typical asphalt binders. Healing indices are put forward, and factors that affect healing performance are examined in this paper. Finally, the fatigue and healing processes of asphalt binder are investigated by analyzing test specimen cross-sections. The findings from this study, although based on a limited number of binders, suggests that HI1 (the modulus ratio) and HI2 (the cycle number ratio) are suitable healing indices. Rest periods and microstructural configurations significantly affect the healing performance of asphalt binder. Healing affects the fatigue performance only when the modulus value is greater than the modulus value when rest periods are applied. During fatigue testing, damage starts at the outer edge of the specimen, and then develops towards the middle of the specimen. [Copyright &y& Elsevier]

Abstract: Low temperature cracking is the major damage in asphalt pavement, and many test methods have been used to evaluate the anti-cracking property of asphalt mixture. This paper evaluates the low temperature performance of asphalt mixture using four tests namely: beam bending test, indirect tensile test, contraction coefficient test and thermal stress restrained specimen test. Five types of asphalt mixtures namely: A, B, C, D and E were evaluated. Results show that compared with the thermal stress restrained specimen test, beam bending test, indirect tensile test and contraction coefficient test are not appropriate for the evaluation of asphalt mixtures low temperature performance. Moreover, results of gray relational analysis demonstrate that the bending strain energy density is significantly correlated to fracture temperature. It is reasonable to adopt the critical values of bending strain energy density to evaluate the low temperature performance of asphalt mixture in the absence of fracture temperature. [Copyright &y& Elsevier]