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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]

Pavements skid resistance, especially in wet states, is an essential indicators of traffic safety. However, the existing testers cannot reflect actual road friction situations and oversimplify water's effect on texture and skid resistance. Therefore, this study compared a traditional British pendulum tester (BPT) with actual vehicle braking. A simplified water coverage simulation programme was proposed, and the BPT characterised the influence of different thin water films on skid resistance in the laboratory. Besides, several freshly constructed road sections (AC-13, SMA-13, and PAC-13) were tested with both BPT and vehicle braking during rainfall. The results showed that water film, even thin, is unfavourable for pavement skid resistance. The BPT results were inconsistent with that of the vehicle braking. Because the tribological properties characterised by BPT are provided by micro-texture and partly macro-texture within the rubber-texture interaction depth (0.1 mm). Larger texture depth and more tortuous and connected pores will offer pavements larger water capacity and higher water permeability, which is beneficial for alleviating braking distance reduction during rainfall. In general, an ideal skid resistance tester should consider characteristics within the rubber-texture contact depth and should consider braking conditions such as speed, water film thickness, drainage method, and slip rate. [ABSTRACT FROM AUTHOR]

The application of reclaimed bio-oil has demonstrated many merits in modifying asphalt rubber (AR). However, the traditional rheological methods tend to be ineffective in scoring asphalt rubber modified by bio-oil (BoAR). This study aimed to assess how asphalt viscoelasticity is affected by the complicated interactions of three components in BoAR. Two different liquid additives were incorporated into AR utilizing three mixing sequences. Then the temperature and time dependence of these BoARs were investigated through the total dissipated energy function and process-accelerated fatigue testing, respectively. Furtherly, the master curves were constructed to detect their overall viscoelastic response. Finally, two evaluating methods, i.e. measured transition temperature and functional analysis region, were proposed by applying the time-temperature superposition principle (TTSP) and statistical methods. As a sequence, adding CRM tends to weaken the bitumen viscoelasticity, whereas the bio-oil presents the opposite result. Also, adjusting manufacturing processes utilizing liquid biological oil was proven a practical approach to optimizing the time-temperature sensibility of BoARs. In addition, the proposed rutting analysis region showed superior representativeness and practicability in evaluating the high-temperature properties of viscoelastic materials. [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]

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]

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]

Pavement surface texture plays a leading role in the tire-road interaction. To increase the understanding of the pavement texture evolution, two typical asphalt wearing courses, Asphalt Concrete (AC) and Stone Mastic Asphalt (SMA), were polished using the real car tires of Harbin accelerated polishing machine (HAPM). After each polishing cycle, the surfaces were reconstructed using X-ray Computed Tomography (CT) technology. Then, the texture evolution was analysed using material area ratio and two-dimensional power spectral density (2D-PSD). In addition, the critical texture wavelength related to British Pendulum Number (BPN) was determined through Pearson analysis. The results show that the texture roughness changes asynchronously at all observed scales (0.1∼80 mm) under the polishing effects. During the short-term polishing, the surface becomes rougher due to bare aggregates and extended gaps caused by the removal of surfacing mortar. With the increasing polishing cycles, the roughness at short wavelengths under 0.6 mm significantly decreases. Meanwhile, the wear rate in the initial stage is higher than that in the subsequent polishing period. The mixture SMA-13 is more wear-resistant than AC-13 during the polishing. It is also found that the texture with a wavelength under 5 mm is well correlated with BPN. [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]

This study focused on the application of Rayleigh wave technology on a non-destructive determination of dynamic modulus of asphalt mixtures. A 3-D finite element numerical algorithm was developed to simulate Rayleigh wave propagation in a multi-layer half-space system. Numerical analysis verified the feasibility of Rayleigh wave technology to capture the mechanical property differences in shallow structures within asphalt pavements. Then, five asphalt mixtures were used in the experimental application of Rayleigh wave technology. A multichannel simulation with one receiver (MSOR) was adopted to generate Rayleigh waves in asphalt mixture samples. Changes in phase velocity-frequency energy spectra and wave velocity were used to evaluate effects of ambient air temperature and asphalt mixture type on wave propagation evolution in asphalt mixtures. Rayleigh wave technology was introduced to dynamic modulus analysis using various experimental temperatures and asphalt mixtures. Obtained modulus was compared with that using impact resonance method to evaluate the prediction precision for analysis dynamic modulus of asphalt mixtures. [ABSTRACT FROM AUTHOR]

The objective of this study is to expose the effect of a variety of variables including three reclaimed asphalt pavement (RAP) contents, two warm mix asphalt (WMA) additives and a rejuvenating agent (or lack of) on the performance of WMA containing (WMA–RAP) materials. A laboratory study was conducted to evaluate the performance of WMA–RAP mixtures through rutting, bending and freeze-thaw splitting tests. Analysis of variance (ANOVA) was performed to analyse the significant effect of the variables on the performance. The tests results showed that the increased RAP content led to an increased rutting resistance and the decreased resistance to low-temperature cracking and moisture damage. The addition of the rejuvenating agent into the WMA–RAP mixtures can significantly improve the low-temperature cracking and moisture resistance. The ANOVA results showed that the RAP content had a significant effect on the rutting and low-temperature cracking resistance, and moreover, the rejuvenating agent (or lack of) had a large effect on the low-temperature cracking and moisture resistance. [ABSTRACT FROM PUBLISHER]