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Fog imposes adverse effect on driving safety. Traditional visibility measurement methods are expensive and limited to a short distance along the roadway. This study aims to identify visibility levels from foggy road images with deep learning methods. To address the shortage of foggy road image data set, a novel method is proposed to generate synthetic fog images based on point cloud and red, blue, & green (RGB) images. A synthetic foggy roadway image data set, kitti-foggy, containing 10,034 images was created with data from the kitti data set. Performance of the proposed method was compared with the traditional stereo-based method. Three typical image classification convolutional neural networks, including ResNet34, ResNet101, and Inception V4, were used to train the data set, and several evaluation matrices were used to evaluate their performances. The proposed method outputs more natural and authentic fog images. ResNet34 demonstrated the best performance among three algorithms with an overall accuracy of about 93%. Real data from a driving recorder and drones was used to verify the capability of ResNet34 to detect real fog. Findings of this study assist in the field of autonomous driving as well as intelligent transportation. [ABSTRACT FROM AUTHOR]

The thermal equilibrium of asphalt mixtures, when combined with reclaimed asphalt pavement (RAP), forms the foundation for high-quality hot pavement recycling. This study focuses on quantifying the thermal equilibrium process of recycled asphalt during mixing. To achieve this objective, a typical RAP content of 20% was utilized in preparing the recycled asphalt. In the experiments, three preheated RAP temperatures were considered to reflect different practical scenarios. Thermal images of recycled asphalt were captured throughout the entire mixing process from 10 s to 90 s in order to characterize the temperature evolution pattern of recycled asphalt mixtures. In addition to experiments, discrete element simulation was conducted to elucidate additional details regarding temperature exchange. The results indicated that the initial thermal equilibrium during mixing may have a significant impact on RAP dispersion and temperature variation, while the subsequent mixing period has limited influence on the final thermal state. Furthermore, it is observed that complete thermal equilibrium cannot be achieved due to the nonuniform distribution of RAP at the end of mixing. In addition, a model describing the temperature evolution of RAP is proposed in this study, which demonstrates a good fit with the data. [ABSTRACT FROM AUTHOR]

The development of modern chemical technology has raised the production of phosphogypsum (PSP) to a new level, while its inappropriate disposal would have a significant risk to the natural environment as hazardous solid waste. As a by-product of PSP refining, the incorporation of phosphogypsum whiskers (PSW) into hot mix asphalt not only mitigates the negative environmental effects of PSP accumulation but also improves the service performance of the modified asphalt, yielding considerable environmental benefits. To facilitate the use of PSW in asphalt pavements, this study employed four surfactants to apply organic coatings to PSW and investigated the surface modification process of PSW. Additionally, rheological tests under different temperatures and stress conditions were conducted to investigate the effects of PSW with modification on the functional properties of asphalt. These tests include the performance grade test, multiple stress creep recovery test, frequency sweep test, time sweep test, linear amplitude sweep test, and bending beam rheometer test. The test results indicated that the incorporation of modified PSW (MPSW) effectively improved the high temperature performance and rutting resistance, and enhanced the fatigue performance to a certain degree, but it also affected the low temperature performance. Moreover, there were some differences in the modification effects for several surfactants, and the aminopropyltriethoxysilane (KH550) exhibited a superior modification effect on PSW compared to other surfactants, and PSW + 10% KH550 + ultrasonic vibration was suggested as the optimal combination. The Fourier transform infrared spectroscopy (FTIR) test results revealed that only physical modification involved in the MPSW modified asphalt. The pavement performance test results showed that the high temperature performance and moisture stability of MPSW modified asphalt mixtures were improved, while the low temperature performance was attenuated, but it was satisfied with the utilization requirement. This study offers a sustainable method for consuming significant quantities of PSW, thereby promoting the resourceful utilization of solid waste and contributing to the sustainable development of asphalt pavement. [ABSTRACT FROM AUTHOR]

Restricted by the harsh environmental conditions in cold regions, the construction of polymer-modified asphalt pavement in these areas is usually a process of high emissions of toxic and harmful gas and large energy consumption. To this end, carboxylated styrene–butadiene latex (XSB) was adopted as a novel modifier, and the mechanical performances of bitumen and asphalt mixture after modification were examined. Research shows that the use of XSB effectively absorbs polar components in bitumen and hinders the formation of bee-like structures, which is manifested by a reduction in the dimension of bee-like structures and microscopic roughness of modified bitumen. The application of XSB dramatically improves the performances of bitumen and asphalt mixture, including rutting, fatigue, low-temperature cracking, and moisture resistance, and the performances of asphalt mixtures after modification can meet the most stringent specification requirements in China when the mass ratio of the XSB reaches 6%. More importantly, compared to a polymer-modified asphalt mixture, the introduction of XSB notably enhances the performances of bitumen and asphalt mixture without increasing the construction temperature of the matrix asphalt mixture, which will significantly reduce energy consumption and lead to fewer toxic and harmful gas emissions. This study presents a potential sustainable solution for asphalt pavements in cold regions, promoting cleaner production while significantly enhancing pavement performance. [ABSTRACT FROM AUTHOR]

Self-healing of asphalt is a potential way to increase the service life of road surfaces. In the past, scientists have employed various methods to enhance the self-healing abilities of asphaltic materials. One of these methods is the application of encapsulated rejuvenating agents to initiate crack-healing by restoring asphalt binder to its initial attributes. The purpose of the current study is to evaluate the fracture resistance of asphalt mixtures and the crack recovery process, which is modified with encapsulated rejuvenating agent derived from waste, specifically soybean sludge (SS) and fatty acids extracted from soybean sludge (SSFA). Two different proportions (0.1 and 0.2) were used for the rejuvenator/water ratio (r/w) for each rejuvenator type and were meticulously examined for their influence on the physical and mechanical properties of the asphalt mixtures. Assessments of self-regeneration were conducted through semicircular bend (SCB) testing employing monotonic loading, measuring fracture resistance and the recuperation of fracture resistance during the postrest period. After this, the results showed that the introduction of capsules did not compromise the mechanical performance of the asphalt mixture, although it did influence crack behavior, resulting in a marginal strength reduction following crack healing. Despite the overall damage incurred, capsule inclusion facilitated the recovery of crack resistance and complete healing. Capsules achieved a peak recovery of 33% with a soybean sludge-to-water ratio of 0.1. Therefore, this study concluded the practicality of this approach and underscore the efficacy of soybean sludge as an encapsulated rejuvenating agent. [ABSTRACT FROM AUTHOR]

Cracking is a serious asphalt pavement distress that can affect ride quality and impact road safety. The increased use of reclaimed asphalt pavement (RAP), recycled asphalt shingles (RAS), and modified asphalt binders has led to the production of asphalt mixtures that are prone to cracking issues. In addition, asphalt aging, which occurs during mix production and construction as well as during pavement service life, is a significant factor that can exacerbate issues related to all modes of cracking. Consequently, the volumetric mix design method alone can no longer secure acceptable long-term pavement performance, and several transportation agencies in Canada currently are integrating performance tests into mix design procedures to increase longevity and durability of asphalt mixtures. This study investigated the influence of common mix design properties on cracking and aging resistance and developed preliminary cracking performance–based specifications for balanced mix design implementation. Six loose plant-produced mixtures consisting of a range of mix design properties were compacted in the laboratory to produce short-term- and long-term-aged specimens. The Illinois flexibility index test (I-FIT) was used to evaluate cracking performance of both short-term- and long-term-aged specimens. The results showed that mixtures with higher nominal maximum aggregate size (NMAS), limestone aggregates, and RAS reduced cracking performance. Conversely, incorporating RAP and RAS and using stiffer binders improved aging resistance, whereas use of limestone aggregates contributed to lower aging resistance. [ABSTRACT FROM AUTHOR]

The development and application of microwave heating technology in asphalt pavement is a hot research topic in the road field. This study aims to delve into the micro-scale properties of asphalt after microwave heating. Based on four-component experiments and infrared spectroscopy experiments, asphalt molecule models, as well as aggregate and moisture models after oven heating and microwave heating, were established using Materials Studio simulation software. The density changes, radial distribution functions, and mechanical properties were calculated using the Forcite module. Additionally, the diffusion and adsorption of asphalt on the surfaces of aggregates and moisture were computed to characterize its bonding characteristics. The research findings indicate that microwave heating leads to changes in the asphalt components, resulting in a corresponding decrease in the molecular density of the asphalt. Due to these component changes, the mechanical properties of the asphalt are somewhat diminished after microwave heating. Microwave heating also results in a uniform dispersion of asphalt components, as evidenced by the radial distribution function, which shows that microwave-heated asphalt is more uniformly dispersed with a reduced packing density. In terms of diffusion and adsorption, the results show that the diffusion coefficients of asphalt on the surfaces of aggregates and moisture decrease after microwave heating, along with a reduction in the interaction energy with aggregates and moisture. This suggests a relative decrease in the activity of asphalt molecules after microwave heating. Similarly, the calculations of interaction energy indicate improved resistance to water aging for asphalt after microwave heating. These research findings provide valuable theoretical guidance for the application of microwave heating in the field of road engineering. [ABSTRACT FROM AUTHOR]

This study explores the optimization of hot mix asphalt (HMA) performance through the incorporation of nano clay (NC) and carbon nano tubes (CNTs) into the asphalt binder. Through a systematic evaluation, the research determines the optimal proportions of these nanomaterials by assessing their impact on crucial asphalt properties, including viscosity, shear modulus, shift angle, stiffness, the slope of the stiffness-time curve, nonrecoverable shear compliance, and percent recoverable strain. The results reveal that an NC content exceeding 0.8% surpasses the Superpave rotational viscosity limit, thereby adversely affecting the workability of the asphalt mixture. Consequently, further testing on NC-modified binder is halted, with the focus redirected to CNTs-modified binder. The optimal CNT content is identified as 1%. At this concentration, the highest rutting parameter ratio (G*/sinδ) is achieved, along with the lowest nonrecoverable shear compliance and highest percent recoverable strain. On the other hand, this CNT content caused a minimal adverse effect from a small increase in rotational viscosity, creep stiffness at low temperature, and fatigue parameter (G*sinδ) at an average service temperature. Additionally, this CNT concentration results in the stiffness-time curve having a steeper slope, indicating less susceptibility to low-temperature cracking. These findings demonstrate that 1% CNTs substantially enhance the rutting and low-temperature cracking resistance without significantly compromising fatigue crack resistance and workability during mixing and compaction. They offer valuable insights into tailoring asphalt binder compositions for enhanced HMA performance. Practical Applications: Numerous studies delved into the use of various polymers as additives and revealed inconsistent improvements across the mechanical properties of HMA. In some cases, these additives have even detrimentally affected HMA performance. Conversely, nanomaterials offer a promising avenue for the development of a new generation of asphalt additives. This study undertakes a comprehensive evaluation process, including an assessment of the rheological behavior, fatigue cracks resistance, and rutting resistance to provide a more holistic understanding of the modified binder's performance. This study yields valuable insights for both the state of the art and/or state of the practice in the field of asphalt technology. The results offer quantitative data on the enhancement of binder performance through nanomaterial utilization, potentially catalyzing further research, influencing industry practices, and fostering the widespread adoption of nanomaterial-modified asphalt binders in pavement construction. This could ultimately lead to safer, more durable, longer-lasting pavements, necessitating reduced maintenance and offering increased cost-effectiveness. This study builds on previous research, refines established methodologies, and proposes modifications to industry standards. Therefore, this study is expected to integrate with or challenge existing knowledge in the realm of the impact of nanomaterials on asphalt binder performance. [ABSTRACT FROM AUTHOR]

The cold-mix asphalt mixture with solvent-based liquid asphalt shows promising application prospects in winter pavement maintenance. This paper evaluates the performance of cold-mix asphalt mixtures in both laboratory and field settings. The initial strength, formed strength, indirect tensile strength, and evolution law were researched through lab tests. The results indicate that the Marshall stability can reach a high level after fully curing. The curing temperature has a more significant influence on the indirect strength compared to the curing time. Uniaxial penetration tests were conducted to investigate the impact of curing states on the strength formation. Observations revealed that strength formation was uneven due to variations in curing conditions. In the field, the patches with different gradations were installed and investigated. Vertical deformation at the different periods was recorded and analyzed. The results reveal that the mixtures with dense gradation perform well in the lab but fail fast in the field, while the mixtures with open gradation are more suitable for pothole repair in winter. The inconsistency between the laboratory and field results is mainly attributed to the strength formation mechanism of the liquid asphalt mixture and the uneven curing in the field. Indeed, the curing condition significantly influences the strength formation process. [ABSTRACT FROM AUTHOR]

Recycled asphalt pavement (RAP) and waste cooking oil (WCO) are considered waste materials with significant adverse effects on the environment. In this study, WCO is investigated as a rejuvenator to incorporate different RAP contents in hot mix asphalt (HMA). The performance of rejuvenated binders and recycled mixtures with optimal doses of WCO is investigated considering rutting, fatigue, and durability characteristics. The binders without WCO depicted significantly higher rutting resistance and poor fatigue life as determined from the linear amplitude sweep (LAS) test. Performance tests showed that recycled mixtures (RA mixtures) with various RAP contents tested at the ideal WCO content and demonstrated rutting and cracking resistance on par with HMA. Additionally, due to the acidic nature of WCO and asphalt, there is an increased affinity for moisture, which leads to moisture damage. Consequently, the moisture susceptibility of recycled mixtures containing WCO was evaluated. Correlations were developed between the rheological characteristics of rejuvenated binders and RA mixtures with WCO. This study recommends incorporating WCO methodically to improve the performance of HMA using various RAP contents. Dry addition of WCO can mitigate moisture susceptibility of recycled mixtures at a higher degree than when using a wet method, and this resistance can be further enhanced using antistripping agents. Practical Applications: This study investigates a significant way to build road infrastructure with sustainability. It demonstrates a simple yet rational method to tackle two environmental concerns related to recycled asphalt pavement (RAP) and waste cooking oil (WCO) by employing WCO as a rejuvenator in recycled hot mix asphalt (HMA). This study reveals that integrating WCO into RAP formulations significantly enhances the performance of rejuvenated binders and recycled mixtures (RA mixtures) with optimal WCO doses. This innovation leads to RA mixtures exhibiting comparable rutting, durability, and cracking resistance to conventional HMA while addressing environmental challenges associated with RAP and WCO. For practitioners and stakeholders in construction and infrastructure, implementing this method presents a sustainable solution to enhance asphalt performance while effectively managing wastes. By incorporating WCO strategically, pavements can be constructed or rehabilitated with the utilization of different RAP contents, promoting environmental sustainability without compromising performance. This research offers a practical pathway for the asphalt industry to embrace a greener approach, potentially revolutionizing road construction practices and contributing to an ecofriendlier infrastructure landscape. [ABSTRACT FROM AUTHOR]

Accurately identifying sealed cracks on asphalt pavement surfaces is of significant importance to pavement management. This paper proposes an efficient semantic segmentation model called Parallel-TDNet for pixel-level detection of pavement sealed cracks. The proposed Parallel-TDNet presents two major modifications of the DeepLabv3+ model. First, the self-attention mechanism is applied at the end of the downsampling process to capture long-range dependency and enhance utilization of global information relationships. Second, a concurrent squeeze and excitation block is added to the original decoder of the DeepLabv3+ model to capture the details of sealed cracks. Experimental results demonstrate that the proposed Parallel-TDNet model on 932 testing images achieves a mean F-measure of 84.83% and a mean intersection-over-union of 0.7366 respectively. Compared with several efficient semantic segmentation models, such as PSPNet, FCN, SegNet, U-net, DeepLabV3+, SegFormer, the Parallel-TDNet algorithm yields a noticeably higher detection accuracy. [ABSTRACT FROM AUTHOR]

As per the performance grading scheme, the selection of asphalt binder for a particular location requires information on seven-day maximum and one-day minimum pavement temperatures. Pavement surface temperatures are usually related to the surrounding air temperature. This study presents a methodology for developing air temperature predictive models using high resolution long-term weather data of India. Gene expression programming (GEP), an evolutionary computing algorithm, was used to evaluate the expressions governing the air temperature as a function of latitude, longitude, elevation, relative humidity, wind speed, solar radiation, and rainfall intensity. A new methodology to evaluate the optimum tree depth for achieving reasonably high accuracy but at reasonably smaller tree depth was also proposed. Statistical analysis involving comparing the goodness of fit and distribution of the prediction error was conducted to understand the prediction capability of the proposed models. The statistical analysis proved the reasonably high predictive power of the gene expressions corresponding to the optimum tree depth. The proposed seven-day maximum and one-day minimum air temperature predictive models have a very simple structure that can be used by field engineers for hand calculation with little effort. [ABSTRACT FROM AUTHOR]

Influenced by aircraft engine wake effects, aggregates stripped off from asphalt runway surfaces are more severe during winter than during the other seasons in cold regions. In this study, five types of asphalt specimens with asphalt–aggregate ratios (AARs) ranging from 3% to 7% were used to assess antistripping performance and foreign object debris (FOD) risk. Freeze–thaw cycles and repeated load tests were performed to obtain the ratio of stripped aggregates (RSA) using three different evaluation methods. The results showed that the RSA was effective in evaluating the antistripping performance of asphalt pavement using the proposed methods. An increase in the RSA was observed with an increase in the number of experimental cycles and a decrease in the AAR. The improved weight loss (IWL), image recognition (IR), and laser scanning (LS) methods showed reliable RSA prediction in different aspects. The IWL method showed high efficiency in estimating general stripped aggregates in large areas but low accuracy in identifying the location and condition of FOD risk. The IR method could accurately determine the area and locations of stripped aggregates. The LS method was the most effective in assessing FOD risk by distinguishing stripped coarse aggregate scaled-off from the surface. The combined applications of these three methods can be a helpful tool for antistripping performance assessments in asphalt runway pavement management in cold regions. In addition, hot mixed asphalt with an AAR between 5% and 6% is suggested for asphalt runway pavement design and construction to improve antistripping performance. Practical Applications: In the management of asphalt runways in civil aviation airports in cold regions, stripped aggregates are a major resource of foreign object debris. Consequently, after repeated operations of removing the stripped aggregates, the pavement performance deteriorates quickly, especially in the landing and takeoff areas. By comparing three methods of evaluating the antistripping performance of asphalt specimens after freeze–thaw cycles, the laser scanning method was proven to be a promising tool for assessing pavement macrotexture. Further laboratory research and in situ experiments are required to develop applicable equipment and conduct validation tests. Using the measured data, airport management agencies can make scientific decisions on maintenance. [ABSTRACT FROM AUTHOR]

In this study, we address the numerical approximation of a class of evolutionary mixed variational problems and its application to the modeling of multi-layer viscoelastic contact systems. The specificity of this problem resides in the introduction of a dual multiplier to decouple and describe the nonlinear unilateral constraint, which renders it advantageous in the study and numerical computation of numerous contact problems. By imposing appropriate regularity conditions, we prove the approximation properties of the solution to its corresponding discrete problem and proceed to discuss its application in asphalt pavement mechanics modeling based on multi-layer contact systems. Particularly, the introduction of time-dependent dual constraint conditions realizes the simulation of time-dependent interlayer contact states, making the model more in line with the evolution process of actual pavement. Several numerical experiments conducted in both two and three dimensions illustrate the nonlinear displacement characteristics within the contact zones and validate conclusions related to error convergence. Furthermore, these experiments demonstrate the effectiveness of this approach in modeling pavement mechanics. [ABSTRACT FROM AUTHOR]

This comparative study presents a detailed experimental investigation to analyse two significant asphalt mix design methods i.e. Marshall and Superpave on the basis of optimum bitumen content (OBC), volumetric properties incorporating air voids, voids in mineral aggregates (VMA) and voids filled with asphalt (VFA) as well as performance evaluation tests encompassing resilient modulus (MR), test, indirect tensile strength (ITS) test and moisture susceptibility test while using the materials procured from the same source and adopting an exactly identical aggregates’ structure. Asphalt mixes for Marshall and Superpave were prepared using their respective design and compaction strategy. The volumetric analysis based results indicate that the Superpave method provides mix with 0.13% lesser OBC, alongwith slightly reduced values of VMA and VFA. The average value of ITS for Superpave sampleswas almost 10% higher as compared to Marshall samples. The difference in terms of moisture susceptibiity was found to be insignificant. Moreover, the results of MR test reveal that Superpave specimens possess 19% higher MR values as compared to Marshall samples at 25°C, 16% higher MR values at 40°C and 15% higher values at 55°C. The outcomes of performance-based testing reflect the potential of Superpave design to enhance the resilience of asphalt pavements. [ABSTRACT FROM AUTHOR]

AbstractTo further understand the effects of fiber type on the properties of different asphalt mastic, basalt fiber (BF), glass fiber (GF) and polyester fiber (PF) were utilized to prepare the corresponding fiber reinforced asphalt mastic samples. Cohesion-adhesion and rheological properties of fiber reinforced asphalt mastic were evaluated by the self-designed low-temperature tensile test, binder bond strength test, temperature sweep test and frequency sweep test. At the same time, the interfacial interaction ability between the fiber and asphalt mastic was quantitatively analyzed based on the complex shear modulus coefficient index. The results showed that adding fibers can significantly improve the ultimate tensile force and tensile fracture energy of the asphalt mastic at low temperature. Fiber has a certain improvement effect on the interface adhesion strength between asphalt mastic and aggregate. Meanwhile, the addition of fiber significantly improves the high-temperature of asphalt mastic. The difference of complex shear modulus of asphalt mastic before and after adding fibers under low-frequency condition is more obvious compared with the high-frequency condition. Furthermore, the type of fiber presents a significant impact on the interfacial interaction between fiber and asphalt mastic, which is also affected by the service temperature. These findings are helpful for understanding the reinforcing mechanism of fibers in asphalt mastic and can guide the selection of fibers in asphalt materials. It is also of great importance for the optimal design and application of fiber-asphalt mixtures as well as for promoting the use of fibers in asphalt pavements. [ABSTRACT FROM AUTHOR]

Continuous loading on asphalt pavements induces fatigue damage at the interface between the asphalt binder and aggregate or within the binder itself. The understanding of asphalt's fatigue response is considered crucial for the prolongation of pavement service life. Variable stress fatigue tests were conducted on asphalt binders, with conditions such as stress amplitude being altered to analyze fatigue performance and life. This study refines asphalt fatigue evaluation systems, introducing a variable stress time sweep test. Modulus recovery after stress changes was revealed through rheological analysis, indicating damage recovery. Fracture surface analysis showed that increased high–stress loadings resulted in reduced edge flow zone width and a flatter surface. Statistical analysis indicated an "exercise effect", enhancing fatigue life in the second stage. Stress transitions altered fatigue crack paths, surpassing Miner's linear criterion prediction. The fatigue life curve was accurately fitted using the two–stage life model, affirming its applicability in evaluating variable stress fatigue tests. [ABSTRACT FROM AUTHOR]

In order to investigate the effects of surface combined body (SCB) type and geosynthetic type on the low-temperature cracking resistance of reinforced asphalt mixtures, low-temperature bending damage tests were conducted on both unreinforced and reinforced double-layer beam specimens, respectively. At the same time, the load–deflection curve during loading was corrected using the linear fitting difference method to determine the mid-span deflection. Then, the low-temperature cracking resistance of the reinforced asphalt mixtures was comparatively analyzed by calculating the maximum flexural tensile strain (ɛB). Finally, the extent to which the geosynthetic type and the SCB type affect the low-temperature cracking resistance of the reinforced asphalt mixtures was investigated by means of a two-way analysis of variance (ANOVA). The results showed that the greater the tensile strength of the geosynthetics, the greater the mid-span deflection and ɛB of the reinforced double-layer beam specimens. The order is carbon fibre geogrid (CCF) > glass/carbon fibre composite qualified geogrid (GCF) > fibreglass–polyester paving mat (FPM) > unreinforced (UN). In the case of reinforcement, the ɛB of the AC-13/AC-20 combination is lower than that of the AC-20/AC-25 combination, with a significant difference, especially in the case of geogrid reinforcement. Analysis by a two-way ANOVA shows that the order of influence on ɛB ranks as geosynthetic type > SCB type. This study provides a scientific basis for the rational selection of carbon fibre geogrid–reinforced asphalt pavement structures. [ABSTRACT FROM AUTHOR]

The granular bases commonly used in the construction of road infrastructure projects often require a high consumption of raw materials. The potential utilization of recycled materials, specifically Reclaimed Asphalt Pavement (RAP) derived from road asphalt pavement demolition, emerges as a promising sustainable advantage for infrastructure projects, considering its potential environmental and cost benefits in other layers of the structure. In this context, this research proposes a feasibility study on the use of RAP as a granular base layer, supported by an advanced laboratory analysis that includes a range of tests simulating the in-service conditions as well as a full-scale demonstration of the material behavior under static and dynamic loads. Various design variables, such as different gradations and binder content, are considered. The results demonstrate that, despite having discontinuous gradation and smaller aggregate sizes than those commonly applied in natural base layers, the evaluated recycled materials exhibit a higher load-bearing capacity and resistance to permanent deformation than the reference materials commonly used as granular bases. Notable enhancements of up to 30% in elastic modulus, coupled with reductions of around 20% in permanent deformations, have been documented using the asphalt cement potential in the old pavement. [ABSTRACT FROM AUTHOR]

The flexible base asphalt pavement is characterized by its excellent performance. A critical component of this structure is the connected layer, which links the surface layer to the flexible base. This layer is located in an area of high-pressure stress distribution within the pavement. The risk of rutting is heightened in the connected layer due to the effects of loads and temperature fluctuations. However, existing studies have not established a correlation between temperature and rutting prediction models for connected layer materials. Therefore, this study aims to accurately characterize the temperature dependence of the rutting behavior of these materials. Firstly, variations in dynamic stability and rutting deformation of connected layer mixtures were investigated under different temperatures and asphalt binder types. Subsequently, a temperature-dependent model of rutting behavior was developed, highlighting the influence of varying temperatures and asphalt binder types. The proposed temperature-dependent rutting model addresses the limitations of traditional models, which fail to accurately describe the rutting behavior of materials under complex working conditions, and provides a scientific basis for optimizing asphalt pavement design and enhancing rutting performance. [ABSTRACT FROM AUTHOR]

Pavement surface distresses are analyzed by transportation agencies to determine section performance across their pavement networks. To efficiently collect and evaluate thousands of lane-miles, automated processes utilizing image-capturing techniques and detection algorithms are applied to perform these tasks. However, the precision of this novel technology often leads to inaccuracies that must be verified by pavement engineers. Developments in artificial intelligence and machine learning (AI/ML) can aid in the progress of more robust and precise detection algorithms. Deep learning models are efficient for visual distress identification of pavement. With the use of 2D/3D pavement images, surface distress analysis can help train models to efficiently detect and classify surface distresses that may be caused by traffic loading, weather, aging, and other environmental factors. The formation of these distresses is developing at a higher rate in coastal regions, where extreme weather phenomena are more frequent and intensive. This study aims to develop a YOLOv5 model with 2D/3D images collected in the states of Louisiana, Mississippi, and Texas in the U.S. to establish a library of data on pavement sections near the Gulf of Mexico. Images with a resolution of 4096 × 2048 are annotated by utilizing bounding boxes based on a class list of nine distress and non-distress objects. Along with emphasis on efforts to detect cracks in the presence of background noise on asphalt pavements, six scenarios for augmentation were made to evaluate the model's performance based on flip probability in the horizontal and vertical directions. The YOLOv5 models are able to detect defined distresses consistently, with the highest mAP50 scores ranging from 0.437 to 0.462 throughout the training scenarios. [ABSTRACT FROM AUTHOR]

• The DNN algorithm was constructed for the small sample data with RMSE of 3.1059e-5. • The DNNSS-APDM-PFC model saves at least 86 % of design time for the CSSWGS gradations. • A set of intelligent methods were proposed to design the gradations of CSSWGS. • The gradation range of CSSWGS used as pavement material was proposed. The utilization of natural waste gravel soil as base course material contributes to environmental protection and carbon emission reduction. The purpose of this research is to establish a new model for automated gradation design of the composite soil stabilizer-stabilized waste gravel soil (CSSWGS). A gradation range of CSSWGS has been proposed. The bearing capacity of the waste gravel soils was analyzed using the Particle Flow Code (PFC). The pavement structure performances of CSSWGS with different gradations were also evaluated using the asphalt pavement design method in China (APDM). A critical scientific challenge is to provide foundational predictive data for the gradation design. To address this, a deep learning neural network for small sample (DNNSS) was constructed to predict unconfined compressive strength (UCS) and frost resistance, offering analytical data for both of the aforementioned software. The Adaptive Moment Estimation (Adam) algorithm was employed to dynamically adjust the learning rate, thereby accelerating network; the Dropout function was used to alleviate overfitting; and the Rectified Linear Unit (ReLU) function was used as the activation function to solve the gradient vanishing problem. The results show that the DNNSS algorithm exhibits superior prediction performance compared to other deep learning algorithms. When employing the web version of APDM and the virtual California Bearing Ratio (CBR) test, the analysis results based on the predicted values from DNNSS and measured values were found to be consistent or closely aligned. Consequently, the new DNNSS-APDM-PFC model, leveraging the intelligent algorithm developed in this study, can be effectively utilized for designing the gradations of CSSWGS or analyzing the gradation performances of CSSWGS obtained from field applications. [ABSTRACT FROM AUTHOR]

Fatigue damage to asphalt pavements due to continuous loading occurs mainly at the binder–aggregate interface or within the asphalt binder. The mechanical response of asphalt binder under variable stress conditions was comprehensively analyzed by repeated loading tests. The viscoelastic intervals of three asphalt binders (Pen70–80, Pen60–70, and SBS) were determined by stress scanning tests, and two different sizes of stresses were selected for constant stress time scanning inside and outside of the intervals based on the experimental thresholds, to provide a reference for the selection of load combinations for variable stress fatigue tests. Cyclic loading of the samples using DSR focused on the complex shear modulus and phase angle behavior of asphalt binder samples under linear viscoelastic (LVE) and nonlinear viscoelastic (NLVE) stresses. The study reveals that under LVE and NLVE stresses, asphalt binders exhibit different mechanical behaviors, each indicating different aspects of damage accumulation and recovery capabilities. Under LVE stress, asphalt binders demonstrate an initial rapid decay of modulus, followed by a phase of slowed degradation and then a swift decline leading to fatigue failure. This pattern contrasts with the response under NLVE stress, where a more pronounced and quicker degradation is observed in both the initial and final phases, indicating significant initial damage. Analyzing the experimental results, at small stresses within the online viscoelastic interval, the modulus decay of asphalt specimens mainly occurs at the late loading stage, and the phase angle growth also occurs mainly at the late loading stage, while at large stresses, the asphalt specimens produce a large amount of modulus decay at the early loading stage. Furthermore, the study explores the NLVE-LVE loading mode, observing a rapid recovery phase in the early stages of the second phase. This phase is characterized by an increase in modulus accompanied by a decrease in phase angle, indicating an increase in the elasticity of the specimen. However, in the LVE-NLVE mode, a rapid accumulation of damage is observed without a similar recovery phase, highlighting the impact of NLVE stress on inducing irreversible damage. The findings suggest a complex interplay between the type of stress applied and the mechanical response of asphalt binders, with significant implications for understanding the fatigue and recovery behavior of asphalt materials under variable stress conditions. The aim is to investigate the mechanical response and damage evolution law of asphalt binder under repeated loading of variable stress to provide reference for material selection and development of durable pavements. [ABSTRACT FROM AUTHOR]

This study aims to gain an in-depth understanding of the research trends in the field of the long-term skid resistance (L-TSR) of asphalt pavement (AP). In this paper, the detection method, decay model, influence factors, and prediction model of the L-TSR of AP are summarized. This paper quantitatively analyzes the skid resistance mechanism of the pavement and elucidates the existing problems and future development directions of the L-TSR of AP. The research indicates that digital image methods and intelligent sensor detection methods are important methods for the skid resistance detection of AP in the future. The indoor test can provide detailed data of material properties and can effectively evaluate the performance of anti-sliding materials under different environmental conditions by simulating the actual road conditions. A quantitative analysis of the skid mechanism of AP can better reflect the actual contact characteristics of the pavement. The combined prediction model combining multiple single models can not only correct the shortcomings of a single model but also greatly improve the calculation accuracy. At present, the research on the L-TSR of AP is insufficient in the aspects of the tire–pavement interaction mechanism, evaluation index, decay model, and combined prediction model, which needs to be further studied from quantitative, time-varying, unified, and innovative aspects. [ABSTRACT FROM AUTHOR]

The rapid growth of automotive intelligence and automation technology has made it difficult for traditional in-vehicle servo systems to satisfy the demands of modern intelligent systems when facing complex problems such as external disturbances, nonlinearity, and parameter uncertainty. To improve the anti-interference ability and control accuracy of the system, this study proposes a joint control method of electronic mechanical braking control combined with the anti-lock braking system. This method has developed a new type of actuator in the electronic mechanical brake control system and introduced a particle swarm optimization algorithm to optimize the parameters of the self-disturbance rejection control system. At the same time, it combines an adaptive inversion algorithm to optimize the anti-lock braking system. The results indicated that the speed variation of the developed actuator and the actual signal completely stopped at 1.9 s. During speed control and deceleration, the actuator could respond quickly and accurately to control commands as expected. On an asphalt pavement, the maximum slip rate error of the optimized control method was 0.0428, while the original control method was 0.0492. The optimized method reduced the maximum error by about 12.9%. On icy and snowy roads, the maximum error of the optimization method was 0.0632, significantly lower than the original method's 0.1266. The optimization method could significantly reduce slip rate fluctuations under extreme road conditions. The proposed method can significantly improve the control performance of the vehicle-mounted servo platform, reduce the sensitivity of the system to external disturbances, and has high practical value. [ABSTRACT FROM AUTHOR]

The aging resistance of asphalt binder is one of the key factors in determining the service life of asphalt pavements. In order to clarify the mechanism of anti-aging additives for improving the aging resistance of asphalt binder, a study based on molecular dynamics simulations was done. The effect of anti-aging additives on the aging resistance of SBS-modified asphalt binder was analysed by molecular dynamics parameters and rheological parameters. The results showed that the molecular model obtained by assembling the molecular structure of four fractions and SBS modifier was reasonable. The diffusion capacity of asphalt binder molecules was weakened after long-term aging. Aged asphalt binder showed a higher energy barrier to change from steady state to unsteady state. The anti-aging additives did not cause significant effect on the distribution of the four fractions in asphalt binder. It inhibited the increase of heavy fractions and intermolecular forces in asphalt binder during long-term aging. It improved the flowability of long-term aged SBS-modified asphalt binder. During long-term aging, the change in diffusion coefficient of asphalt binder with additives was about 50.4% of that of asphalt binder without additives. The research results provide a convenient way to choose the anti-aging additives. [ABSTRACT FROM AUTHOR]

This study addresses the challenge of icy asphalt pavements in cold climates by proposing an innovative and eco-friendly deicing material. Traditional approaches, such as salt spraying and mechanical deicing, often lead to environmental concerns and increased resource usage. In response, this paper introduces a novel ferric oxide–modified emulsified asphalt (FO-EA), formulated by integrating ferric oxide (FO) powder with emulsified asphalt (EA). Experimental results, including segregation tests and fluorescence microscopy, confirm that 20% by weight of FO is evenly dispersed in the EA. Remarkably, FO-EA–coated asphalt demonstrates a 50% reduction in microwave deicing time compared to conventional asphalt, with a significant increase in the heating rate of 0.12°C/s. In addition, FO-EA surpasses standard asphalt in skid resistance and water seepage tests, meeting all specification requirements. Furthermore, its deicing efficacy remains robust after 500 abrasion resistance test cycles. Overall, FO-EA emerges as an efficient and sustainable solution for road deicing. [ABSTRACT FROM AUTHOR]

The use of reclaimed asphalt pavement (RAP) has brought enormous potential economic and environmental benefits to society. However, the cluster phenomenon of RAP particles in recycled hot-mix asphalt (HMA) has limited the extensive usage of RAP to a certain extent. Therefore, this research evaluated the effect of the original clustering degree of RAP and design parameters on the properties of recycled HMAs and the qualitative status of RAP cluster in recycled mixes. Six groups of mixes were designed, including one control group in which the RAP particles were designed as completely no cluster status, three experimental groups in which the RAP particles were designed at different original clustering degrees, and another two groups designed under different preheating temperatures and blending time. Then, the volumetric indicators, water stability, rutting, thermal cracking, and abrasion performance of each group were evaluated. It can be found that the RAP cluster was partially dispersed during the mixing and varied with different design parameters. The incomplete dispersion of fine RAP cluster acted as a "fake coarse aggregate" and affected the volumetric results and performance of final mixtures. Therefore, it may be inaccurate to design the aggregate gradation of recycled HMAs solely based on the extracted curve or the black curve of original RAP particles. The dispersion process of the RAP cluster during the mixing should not be ignored. In addition, the results also indicated that the original clustering degree of RAP particles may need to be carefully controlled during the construction. [ABSTRACT FROM AUTHOR]

The migration of reclaimed asphalt pavement (RAP) mastic into the recycled hot-mix asphalt (RHMA) mixture system during the hot-mix process results in varying dispersion degrees of RAP aggregates within RHMA, impacting its durability. This study aimed to investigate the impact of hot mix parameters on RAP dispersion and RHMA performance. The dispersion degree of RAP aggregates in RHMA was determined through slicing and digital image processing. The influence of hot mix parameters on RHMA performance was assessed through rotary compaction, Marshall, moisture-induced sensitivity, and low-temperature bending beam tests. The correlation between the RHMA performance and RAP dispersion degree was analyzed by employing the Pearson correlation coefficient. The findings show that higher RAP content reduces the RAP dispersion degree, whereas the opposite trend was observed for the RAP preheating temperature, RHMA mixing temperature, and RHMA mixing duration. Improving the RAP dispersion degree in RHMA decreased the compacted energy index and air voids in RHMA, thereby enhancing the Marshall stability, moisture stability, and low-temperature crack resistance of RHMA. [ABSTRACT FROM AUTHOR]

In recent years, the employment of rejuvenators and warm mix asphalt (WMA) additives for reclaimed asphalt pavement (RAP) has been recognized as a popular approach to increase the recycling rate of waste materials and promote the sustainable development of pavement engineering. However, the composition of warm mix recycled asphalt binder is complicated, and the microstructural changes brought about by the rejuvenators and WMA additives are critical in determining its macroscopic mechanical properties. This research focuses on the atomic modeling of the rejuvenators and WMA additives diffusion behavior of the warm mix recycled asphalt binder. The objective is to reveal the thermodynamic performance and diffusion mechanism of the WMA binder under the dual presence of rejuvenators and WMA additives. Three types of mutual diffusion systems (Aged and oil + virgin + wax, Aged + virgin + wax, and Aged and oil + virgin) were established, respectively, for a comparative investigation of the glass transition temperature, viscosity, thermodynamics, free volume, and diffusion behavior. The results indicate a 44.27% and 31.33% decrease in the glass transition temperature and apparent viscosity, respectively, after the incorporation of 5% oil rejuvenators in the Aged + virgin + wax asphalt binder, demonstrating the improved cracking resistance and construction workability. The presence of the RAP binder and organic WMA additives raised the cohesion of the asphalt binder and decreased self-healing ability and free volume, and these detrimental influences can be offset by the introduction of rejuvenators. The combined use of rejuvenators and organic WMA additives remarkably enhanced the de-agglomeration to asphaltenes, stimulated the activity of aged RAP macromolecular components, and ultimately improved the blending efficiency of virgin binders with the overall structure of RAP binders. [ABSTRACT FROM AUTHOR]

Aiming at the problem that asphalt pavement materials in plateau areas are vulnerable to freeze-thaw damage, research was carried out on asphalt pavements of representative road sections, and the temperature within the pavement structure was monitored using buried sensors. Based on this, an indoor test method for high-frequency freeze-thaw was established, and UV, thermo-oxygen-aging and high-frequency freeze-thaw tests were combined. The effects of aging and maximum aggregate particle size on the resistance of asphalt mixtures to high-frequency freeze-thaw were investigated using the splitting strength ratio, mass-loss rate and void-ratio changes by employing the newly made RS-type modified asphalt in the laboratory. At the same time, the high-frequency freeze-thaw resistance of the asphalt mixture was compared with that of the SS/SMA-13 asphalt mixture on the top layer of a representative road section. The results show that UV aging at 180 h followed by thermal-oxygen aging at 120 h has the greatest impact on the asphalt mixture; in this condition, the high-frequency freeze-thaw-cycle asphalt mixture with freeze-thaw damage is affected by the rule of change of the third-degree polynomial. In the plateau environment conditions, compared with the original pavement material (SS-type modified asphalt), the RS-type modified asphalt has better anti-aging properties, adhesion properties and elasticity performance. [ABSTRACT FROM AUTHOR]

The chemical composition of asphalt binder is closely related to its macroscopic properties, and as an important road building material, its performance directly affects the service performance of asphalt binder pavement. Saturate, aromatic, resin, and asphaltene are the four most common chemical components of asphalt binders, collectively known as the SARA components. The SARA components are used to establish the corresponding relationship between the chemical composition and the macroscopic properties of asphalt binder, which is of great significance for further research on and development of high-performance asphalt pavement materials. This study used eight types of virgin asphalt binders as raw materials, labeled A–H. Firstly, the thin-layer chromatography–flame ionization detection (TLC-FID) method was used to test the SARA contents of the different asphalt binders. Then, the conventional, rheological, and low-temperature properties of the different binders were tested. Finally, gray relational analysis (GRA) and Pearson correlation analysis (PCA) were used to study the correlation between the asphalt binder's SARA content and its macroscopic properties. The results indicate that the contents of asphaltenes and resins are crucial in determining the high-temperature performance of asphalt binder. By adjusting the ratio of these components, the high-temperature performance of asphalt binder can be optimized. An increase in the content of heavy components, particularly asphaltenes, negatively affects the low-temperature performance of asphalt binder. In contrast, a higher aromatic content enhances its low-temperature performance. [ABSTRACT FROM AUTHOR]

Reclaimed asphalt pavement (RAP) has grown in popularity in recent years due to its potential to blower costs and minimize negative effects on the environment. RAP incorporation, however, can also significantly influence the mechanical characteristics of asphalt mixtures, which can impact their general effectiveness and longevity. Due to their potential to improve the qualities of revitalized mixes with RAP, waste materials like waste engine oil (WEO) and waste cooking oil (WCO) have attracted interest for use in asphalt mixtures. This study focuses on predicting and optimizing the mechanical properties of revitalized asphalt mixtures using WCO and WEO along with RAP, particularly the modulus of resilience (MR) and indirect tensile strength (ITS). Classification and regression tree (CART) models were developed to forecast MR, ITS, and ITS loss% for asphalt mixes. It was found that the models could accurately predict the experimental data. With a WCO rejuvenator employed in less than or equal to 16.5% proportion, maximum MR and ITS were achieved. To get maximum MR, the asphalt content should not be more than 5.1%. On the other hand, WEO rejuvenator, asphalt content greater than 5.1%, and RAP content not greater than 45%, were used to achieve maximum durability (lowest ITS loss%). A 5% increase in the loss value is the result of choosing the design that provides the most strength. The study's results encourage the adoption of environmentally friendly pavement building techniques by effectively reusing waste materials and improving the mechanical properties of revitalized asphalt mixtures. [ABSTRACT FROM AUTHOR]

Recently, due to global climate change, extreme weather events have occurred frequently. While the majority of roads in China are constructed using asphalt pavement, the current unmodified asphalt has been unable to withstand the growing axle load and harsh weather conditions. Consequently, this situation significantly impacts the lifespan of asphalt pavement. This study proposes an improved asphalt performance based on organic vermiculite inorganic nano materials, and designs experiments for analysis. Then, it combines atomic force microscopy and nuclear magnetic resonance methods to analyze the microscopic molecular composition of asphalt materials. The grayscale correlation method is used to analyze the macroscopic physical rheological indicators and microscopic component changes, molecular structure and other indicators of asphalt. Experiments showed that compared with macroscopic physical and rheological aging indicators, the modulus growth rate was the highest and the residual roughness was the lowest. The rutting factor approached 0 as the temperature rose around 50°C. The deformation of ZnO was similar to that of the base asphalt, with the smallest degree of modification and the strongest modification ability of TiO2. The softening points of 70# matrix asphalt, ZnO, TiO2, and SiO2 were 49.5, 51.2, 48.9, and 54.6, respectively. Furthermore, the modified asphalt exhibits enhanced stability at high temperatures, indicating the effectiveness of incorporating inorganic nano materials to improve the performance of matrix asphalt. This finding can significantly contribute to the wider adoption and engineering development of asphalt pavement. [ABSTRACT FROM AUTHOR]

To address the insufficient interlayer bonding performance and high preparation costs associated with conventional prime coat materials for semi-rigid base asphalt pavement, in this study, we utilized waste bio-oil to enhance asphalt–aggregate separation in recycled asphalt pavement (RAP) and collected the filtrate after separation. The RAP–bio-oil filtrate acts as a diluent, which is reintroduced into the asphalt to form a novel prime coat material: RAP–bio-oil filtrate cut-back asphalt (RFCA). The optimal proportions of each component in RFCA were determined through penetration tests, interlayer shear tests, and interlayer tensile tests. Subsequently, interlayer shear strength tests were conducted to evaluate the bond strength of RFCA compared to traditional prime coat materials, such as PC-2 emulsified asphalt (PC-2 EA) and kerosene cutback asphalt (KCA). Additionally, interlayer shear fatigue tests were performed to assess the durability of the bond provided by RFCA between the surface and base layers. The experimental results indicate that the optimal formulation for RFCA comprises 60% asphalt by mass of the RAP–bio-oil filtrate and 10% penetrant agent by mass of the RAP–bio-oil filtrate. Under conditions of 15 °C, 40 °C, and 15 °C water immersion, the interlayer shear strength of RFCA demonstrates an enhancement compared to PC-2 EA and KCA. Compared to PC-2 EA, the interlayer shear fatigue life of RFCA improved by 39.7% at a stress ratio of 0.2, 40.8% at 0.3, 51.2% at 0.4, and 40.3% at 0.5. The application of RFCA as a prime coat material significantly enhances interlayer durability. Based on the cost analysis, the application cost per square meter for RFCA is lower than that of PC-2A. Consequently, RFCA presents a viable option as a green, renewable, low-cost, and high-performance prime coat material for application on semi-rigid base asphalt pavement. [ABSTRACT FROM AUTHOR]

The incorporation of waste fluid catalytic cracking (FCC) catalysts (WFCs) into asphalt pavements represents an effective strategy for resource utilization. However, the influences of the composition of the waste catalyst and its surface characteristics on the performance of asphalt mortars are still unclear. Herein, five WFCs were selected as powder filler to replace partial mineral powder (MP) to prepare five asphalt mortars. The diffusion behaviors of asphalt binder on the components of WFCs were investigated based upon molecular dynamic simulation, as was the interfacial energy between them. The adhesion work values between asphalt and WFCs were evaluated based upon the surface free energy theory. A dynamic shear rheology test and multiple stress creep recovery test on the WFC asphalt mortar were also conducted. Furthermore, the gray correlation analysis (GCA) method was employed to analyze the correlation between the diffusion coefficient and interfacial energy with the performance of WFC asphalt mortar. The results showed that the asphalt exhibited a low diffusion coefficient and high interfacial energy with the alkaline components of WFCs. The adhesion work values between asphalt and WFCs are higher than those with MP. The addition of WFCs can enhance the anti-rutting property of asphalt mortar significantly. Among the five WFCs, 2# exhibited the best improvement effect on the anti-permanent deformation ability of asphalt mortar, which may be due to its large specific surface area and moderate pore width. The GCA results suggest that the diffusion coefficient and interfacial energy strongly correlated with the performance of asphalt mortar, with an order of adhesion > permanent deformation resistance > rutting resistance. This study provides both theoretical and experimental support for the application of WFCs in asphalt materials. [ABSTRACT FROM AUTHOR]

Cigarette butt (CB) waste is abundant and difficult to biodegrade, which is dangerous for both the environment and human health. The key reason CBs are littered is that people do not know much about the harm CBs pose to the environment. Recycling CBs in infrastructure construction can help raise people's awareness. To promote the recycling of CB waste, this paper aimed to determine the feasibility of using CBs as a modifier for asphalt binders. In this research, CBs were preprocessed and mixed with virgin asphalt binder as a fiber modifier. Comprehensive laboratory investigations, including a softening point test, viscosity test, storage stability test, and temperature sweep test, were performed, along with a frequency sweep test, to evaluate the performance of the modified samples. During this investigation, samples were prepared with 1%, 2%, 3%, and 4% CBs. The results of the CB-modified samples were compared with the sample consisting of fresh bitumen (0% fiber). The results show that the physical and rheological properties of bitumen with incorporated CBs improved significantly, and CBs could be used instead of virgin cellulose fiber as a fiber modifier. However, CB-modified asphalt reduced the storage stability and low-temperature performance of the samples. Further research should focus on improving the storage stability and low-temperature performance of CB-modified asphalt binders to facilitate their application in asphalt pavements. [ABSTRACT FROM AUTHOR]

This paper presents gradations of both Hot In-place Recycling (HIR) and Cold In-place Recycling (CIR) and analysis of cores collected from CIR/Hot Mix Asphalt (HMA) overlay sections in Iowa. Milling samples were obtained from an HIR recycling project on IA 22 in Wellman, Iowa. It was concluded that the average gradation of HIR millings was coarser than that of CIR millings by retaining the original aggregate gradations. Cores were then extracted from CIR pavement with foamed asphalt overlaid by HMA at the right wheel path and between wheel paths at eight locations on US 34 in Mills and Wapello Counties. The cores were cut into discs to isolate the pavement layers, and the discs were fabricated into semicircular bending test specimens. Based on the Semicircular Bending (SCB) tests performed on both CIR and HMA specimens, CIR specimens with higher asphalt binder contents exhibited higher flexibility index values. Since CIR pavement layers were found to be more flexible than the HMA overlay layers, it can be speculated that CIR layers may serve as a stress-relieving layer and mitigate reflective cracking. [ABSTRACT FROM AUTHOR]

This study investigates the performance enhancement of asphalt and its mixtures through modification with varying contents of styrene–butadiene–styrene (SBS) and rock asphalt (RA). A series of laboratory tests were conducted to comprehensively evaluate the effects of SBS and RA modification. The results demonstrated that SBS significantly improves elasticity, low-temperature ductility, and resistance to fatigue and rutting, while RA enhances high-temperature stability, water stability, and stripping resistance. The synergistic effects of SBS and RA were evident, with the 4% SBS/10% RA mixture achieving the best comprehensive performance, which was characterized by improved high-temperature stability, low-temperature performance, and durability. Conversely, 15% RA content was found to reduce low-temperature flexibility and fatigue performance. A radar chart-based evaluation further confirmed the optimal performance of the 4% SBS/10% RA combination. These findings provide valuable guidance for selecting appropriate SBS and RA proportions tailored to specific performance requirements in asphalt pavement applications. [ABSTRACT FROM AUTHOR]

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Stone base course filled with cement stabilised macadam (SFC) is a promising solution for addressing reflection cracks in semi-rigid base asphalt pavement due to its satisfactory crack resistance. However, its limited strength and construction challenges have impeded its widespread application. To overcome these challenges, an optimised mix proportion design method of SFC was proposed. Natural crushed limestones with specific particle sizes were selected to serve as skeletal coarse aggregates; fine aggregates and their proportions were step-by-step determined using aggregate and unconfined compressive strength tests. The multi-scale analysis integrating the performance tests and the microscopic detections was performed to evaluate the effectiveness of the proposed SFC, and compared with common cement stabilised macadam (CSM). The results indicate that the material exhibits satisfactory mechanical strength through a tightly interlocked skeleton structure and excellent crack resistance by dissipating strain energy and retarding cracking of SFC through the weak interface transition zone (ITZ). [ABSTRACT FROM AUTHOR]

Road infrastructure, fundamental to daily life, inevitably sustains damage over time. Timely and precise identification and remediation of road defects are critical to prolong the lifespan of roads and ensure driving safety. Given the limitations of the widely-used You Look Only Once (YOLO) algorithm, including its insufficient receptive field and suboptimal detection accuracy, this paper introduces a novel road defect detection method. First, we propose a new attention mechanism, aggregate multiple coordinate attention, that effectively retains and concatenates channel information while preserving localization data, thereby enhancing the focus on intrinsic features. Second, we design a cross stage partial—partially transformer block (CSP_PTB) that combines CNNs and transformers to yield richer and more varied feature representations. Finally, we develop a novel neck structure, the re-calibrated feature pyramid network (Re-Calibration FPN), which selectively combines boundary and semantic information for finer object contour delineation and positional recalibration. Experimental results show that the S version of the algorithm in this paper achieves a detection accuracy of 73.2% on the road defect dataset, which is 4.2% higher than the YOLOv8 algorithm. Additionally, with an FPS of 80, it meets the requirements for real-time detection, achieving a good balance between detection speed and detection accuracy. Additionally, it exhibits excellent generalizability and robustness on the UAV asphalt pavement distress and PASCAL VOC 2007 datasets. [ABSTRACT FROM AUTHOR]

Fibers have been widely adopted in asphalt mixture to improve its pavement performance. Lignin fiber and polyester fiber are the most popular two choices. Lignin fiber is derived from wood, which is not aligned with the principles of sustainable development. The production process for polyester fiber is more complex and costly, presenting both environmental and economic challenges in engineering applications. In contrast, basalt fiber is cost-effective, exhibit excellent wear resistance and impact toughness, and possess high mechanical strength. It is an ideal choice to improve pavement performance of asphalt mixtures. However, most of the existing studies focused on analyzing a single characteristic index of basalt fiber. They neglected the composite effects of geometric characteristics of basalt fiber, such as fiber diameter and length, on the pavement performance of asphalt mixtures at varying fiber contents. Therefore, taking the SMA-13 as an example, the combined effect of basalt fiber geometrical characteristics (fiber diameter, fiber length, and fiber content) on pavement performance are elucidated. Additionally, a random forest algorithm is adopted to perform a weight analysis of fiber characteristics and their correlation with pavement performance. [ABSTRACT FROM AUTHOR]

The ride comfort of vehicles traveling on the road has always been a concern. In addition, the braking force of vehicles will aggravate the damage to road structures and reduce the comfort of drivers and passengers. In the present study, the dynamic response of pavement, road friendliness, and human comfort are investigated by setting up the human-bus-road coupled vibration system considering the braking forces. Firstly, the three-dimensional finite element model of asphalt pavement with interlayer contact and the human-bus model with multiple degrees of freedom (2n + 7) were established to analyze the dynamic responses of asphalt pavement, human body, and bus under different braking conditions. Then, the dynamic load coefficients of wheels under different combined conditions were investigated to evaluate the road friendliness and the human annoyance rate was adopted to evaluate the human comfort. The results show that for the asphalt pavement, the shear stress of the pavement is larger than the normal stress due to the bus braking, and the combined effect of road surface roughness and braking force on the road friendliness is the largest. For the human comfort, the pitch acceleration of human body increases more than the roll acceleration due to bus braking, resulting in the decreased human comfort and increased annoyance rate. [ABSTRACT FROM AUTHOR]

The global asphalt production growth rate exceeded 10% in the past decade, and over 90% of the world's road surfaces are generated from asphalt materials. Therefore, the issue of asphalt aging has been widely researched. In this study, the aging of asphalt thin films under various natural conditions was studied to prevent the distortion of indoor simulated aging and to prevent the extraction of asphalt samples from road surfaces from impacting the aged asphalt. The aging of styrene–butadiene–styrene (SBS)-modified asphalt was simulated at four different locations on an asphalt road surface. The aging characteristics of asphalt binders across various structural layers were revealed using Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and linear amplitude scanning (LAS). The results indicate that the aging behavior of the asphalt functional group on the road surface differs from other conditions; the asphalt fatigue life of 4 months equates to the 16-month aging life of asphalt within the dense-graded asphalt road surface. After 8 months of aging, the surface smoothness of the asphalt was significantly compromised. Inside of the porous pavement, the asphalt functional group is more likely to interact with water molecules than inside the dense pavement with cracks, and the variations in roughness and the reduction in fatigue life are also more significant. [ABSTRACT FROM AUTHOR]

In hot weather, asphalt roads can suffer from plastic deformation due to high temperatures, causing ruts and reducing their lifespan. Heat pipes, efficient heat transfer devices, have the potential to cool asphalt roads. This study aims to assess their performance through a thermal resistance network model and numerical simulations. Results show that using heat pipes can reduce the average temperature of AC-16 C asphalt layers by 24.5 °C and AC-25 C layers by 31 °C. Closer spacing and lower cooling water temperature improve cooling. These findings are crucial for optimizing heat pipe cooling systems and improving asphalt road heat dissipation, benefiting road engineering. [ABSTRACT FROM AUTHOR]

One of the most commonly observed distress in asphalt pavement is shrinkage cracking, which has a significant negative impact on the service life of asphalt pavement. The primary purpose of this study is to evaluate the effects of shrinkage or transverse cracking of asphalt pavement on the load transfer efficiency (LTE) by using data obtained from the portable falling weight deflectometer (PFWD) device. So, the pavements of two roads, which were different in thickness, asphalt mix design, and service life, were chosen. The deflections of about 800 different transverse cracks were then measured by the PFWD device. After the evaluation of the collected data, a new equation was proposed for the calculation of the LTE, which is expected to be more accurate than previous equations. A Finite Element (FE) model was then developed by ABAQUS to investigate the LTE of transverse cracks with high accuracy. After the comparison between the developed model and the collected data, the correctness of this model was verified. Also, the effects of some important factors, including the asphalt concrete thickness, and asphalt concrete and base course modulus on the LTE, were investigated in the FE model. The results of field data and FE analyses indicated that the LTE of transverse cracks in asphalt pavement depends on both cracks' widths and the asphalt layer's thickness. The results revealed that when the cracks' widths and the thickness of the asphalt layer increase, the LTE value decreases. Moreover, the results of the FE model analysis for the asphalt concrete and base course indicated that the effect of the asphalt concrete modulus on the LTE was negligible; however, the base course modulus had a considerable impact on the LTE. Hence, the LTE values can be estimated by using the developed model, transverse cracks' widths, and the thickness of asphalt pavement without using the PFWD device. [ABSTRACT FROM AUTHOR]