The years we are experiencing are often identified as those of the age of digital technologies, where "digital" is commonly associated with intelligence, efficiency, and convenience. The emergence of digital technologies has significantly impacted and transformed various aspects of our society compared to the past. In this panorama, some arising questions regard transportation infrastructure systems and, first of all, highway infrastructure. This research focuses on one central issue: how highways fit into this digital revolution. Actually, the work in this paper can be described as follows. Although there are many different theoretical model systems for the architecture of the digital twin, we have chosen to review the main body of research on the digital twin in highway infrastructure based on a relatively well-established modeling framework, the five-dimensional model of the digital twin. After discussing the components of the digital twin for highway infrastructure’s five-dimensional model, the paper reviews some innovative technologies that make these items effective. In addition to this, the digital twin maturity level of highway infrastructure and the MBSE-based (model-based systems engineering) digital twin model for highway are also discussed in this paper. Therefore, the paper provides a bird's eye view of this extremely dynamic technology for a new system of intelligent highways and discusses some of their criticalities and strengths, allowing for the optimization and development of new transportation functions and services, improving the adaptability of highways to the digital revolution.

为了从分子水平揭示餐饮废油(CWO)对老化沥青的再生机制,利用分子动力学和密度泛函理论方法分析CWO对老化沥青胶体性质的影响.通过溶解度参数和密度验证了构建的基质沥青,老化沥青及CWO再生沥青模型的合理性.从径向分布函数和沥青质二聚体结构角度探讨了加入CWO前后老化沥青胶体结构的演化规律及成因;从内聚能密度,剪切黏度,玻璃化转变温度角度表征了CWO对老化沥青胶体热力学性质的恢复效果.结果表明,老化破坏了沥青的溶-凝胶体结构,使其内部形成了致密的沥青质分子团聚.CWO发挥了解缔沥青质团聚的作用,部分恢复了老化沥青胶体的微观结构.与老化沥青质二聚体随机接触的CWO小分子占据了部分结合空间,通过物理空间阻隔使老化沥青质二聚体的结合距离由3.894?增加至4.773～5.044?之间,而结合能由68.482 Kcal/mol降低至40.157～55.376 Kcal/mol之间.与含氧端部相比,CWO分子的不含氧端部和中部更显著地削弱了老化沥青质二聚体的结合强度.CWO恢复了老化沥青胶体的微观结构,降低了老化沥青分子间的作用强度,一定程度上扭转了老化对沥青性能的负面影响,表现为CWO再生沥青的剪切黏度和玻璃化转变温度等热力学性质得到改善.研究成果有利于深入认识CWO对老化沥青的再生机制,也进一步证明了CWO作为老化沥青再生剂的潜力.

生物油是一种绿色、环保、可再生资源,具有恢复老化沥青物理、流变性能,改善再生沥青混合料路用性能的潜力.为了推动生物油在老化沥青材料再生领域的深入研究,概述了生物油的来源、制备及物化性能,探讨了生物油对老化沥青的再生机制,综述了生物油再生沥青和生物油再生沥青混合料的性能,围绕生物油再生老化沥青材料现有研究存在的不足,阐述了后续的研究方向.研究现状表明,压榨油类生物油在老化沥青材料再生中的应用研究较为系统,其次是富木质纤维植物基生物油,动物粪便类生物油的应用研究相对最少,但这3种类型生物油在老化沥青材料再生中均具有广阔的应用前景.富木质纤维植物基和压榨油类生物油在老化沥青再生中既发挥"稀释"作用,也体现出"溶解"作用,从化学平衡和分子结构修复2个层面实现老化沥青的再生;动物粪便类生物油在老化沥青再生中主要发挥"溶解"作用,通过其富含的极性酰胺基团化合物促进了沥青质聚集体的解缔,从分子结构修复层面实现老化沥青的再生.此外,富木质纤维植物基和压榨油类生物油可直接用于老化沥青再生,而动物粪便类生物油更适合与富油再生剂复配应用,由此才能充分发挥再生作用.在这些生物油中,压榨油类生物油体现出更好的再生老化沥青材料的效率.未来的研究应从以下几个方面进行:建立生物油来源、制备工艺与其物化性能的关联性,以便更好地甄别和评估不同来源和制备工艺的生物油作为沥青再生剂的适用性;进一步探索富木质纤维植物基、动物粪便类生物油在老化沥青材料再生中的应用潜力;重点关注生物油再生沥青和再生沥青混合料的二次老化问题;探索生物油在老化沥青材料再生领域的复配应用.

The application of waste vegetable oil (WVO) in bitumen has been the subject of research for years, however, the self-healing behavior of WVO modified bitumen (WMB) has not been adequately reported. In this research, molecular dynamics (MD) simulations and laboratory experiments were performed to reveal the effects of WVO on the self-healing behavior of bitumen. Models of base bitumen and WMB were constructed. Further, dynamic calculations were carried out for the self-healing models of base bitumen and WMB both with 10 angstrom microcracks. The energy properties, conformation and density of bitumen during the self-healing process were analyzed. Meanwhile, the effects of WVO on the fractional free volume (FFV) of bitumen, the distribution of bitumen components and the mobility of bitumen molecules were investigated. Finally, the modified fatigue-healing -fatigue (FHF) test was conducted to verify the effects of WVO on the self-healing efficiency of bitumen. Re-sults show that Van der Waals forces drive the mobility of bitumen molecules. Along with the disappearance of the central microcrack, the density of the self-healing system gradually increases and finally reaches that of the bulk bitumen. WVO with superior mobility capacity increases the FFV of bitumen and converts asphaltene large aggregated structure into small aggregated structure, which facilitates the mobility of the bitumen during the self-healing process. Thus, the addition of WVO contributes to the self-healing efficiency of the bitumen. The modified FHF test also verified that the self-healing efficiency of bitumen is improved with the presence of WVO. These findings provide further insight into the self-healing behaviors of WMB.

Dry modification of modified asphalt mixtures prepared by mixing the modifier with the aggregate and asphalt binder is a simple and environmentally friendly process. It can avoid the segregation of modified asphalt used for paving mixes under wet modification mode. The difficulty of rapid swelling makes it difficult for the styrene-butadiene-styrene block copolymer (SBS) modifier to achieve dry modification. This research attempted to prepare a multi-component SBS-based (SBSM) modifier for dry modification by blending SBS with assisting ingredients through a twin-screw extruder. The conventional properties, rheological properties, and thermal storage stability of SBSM-modified asphalt were evaluated. Additionally, the road performance of SBSM-modified asphalt mixtures prepared by both wet modification and dry modification was characterized. The results show that SBSM-modified asphalt obtains excellent high-temperature and low-temperature properties as well as thermal storage stability. Satisfactory performance in terms of resistance to high-temperature rutting, low-temperature cracking, and water damage is obtained when the SBSM modifier was applied in modified asphalt mixtures under wet modification. Compared with the SBSM-modified asphalt mixture under wet modification, the road performance of the SBSM-modified asphalt mixture under dry modification is slightly inferior, especially the water stability, but satisfies the engineering requirements. The findings demonstrate the feasibility of the dry modification of the SBSM modifier for paving mixtures and promote the development of SBS-based modifiers for dry modification.

This research investigated the effect of aging on the adhesion properties between asphalt and aggregate at the molecular level. Based on the molecular dynamics simulation method, the adhesion characteristics of asphalt component representative molecules and bulk asphalt with silica mineral aggregate before and after aging were evaluated in terms of adsorption energy and adhesion work, respectively. In addition, the simulation results were verified using a pull-off test. Results show that the adsorption energy increases after aging, and was most pronounced for the representative molecules of the asphaltene component. In bulk asphalt, the increase of large-mass molecules after aging led to an increase in its adhesion to mineral aggregate. The presence of water greatly weakened the adhesion strength between asphalt and mineral aggregate, and the negative effect of water on the adhesion strength between aged asphalt and mineral aggregate was severer. The pull-off test confirmed that aging enhanced the adhesion strength between asphalt and aggregate, but exacerbated the negative impact of water on the adhesion strength between asphalt and aggregate. The findings promote further understanding of the effect of aging on the adhesion properties of asphalt to mineral aggregate and the water damage mechanism of asphalt mixtures.

Inverted asphalt pavement (IAP) has the advantage of maintaining good performance under the condition of thin asphalt concrete (AC) layer compared with conventional flexible asphalt pavement. The stress-dependent property of unbound aggregate base (UAB) plays an important role in mechanistic responses of IAP. The focus of this paper is to quantitatively analyze the function of UAB's stress-dependent property on the structure combinations design of IAP using response surface method (RSM). In this paper, an improved UMAT subroutine was developed to characterize the stress-dependent stiffness of UAB. The three-dimensional FE pavement model was established and validated against KENLAYER calculation and field FWD test deflection data. The critical mechanical response, maximum principal strain and bulk stress, were selected to evaluate the fatigue performance of AC layer and stress-dependent property of UAB. The significance analysis was conducted to describe the relationship between input variables (thickness and stiffness of structural layers) and the critical mechanical response variables. An optimization design method to balance the fatigue performance and stress-dependent property was proposed to obtain the optimal structure combinations of IAP. Research results demonstrate that the thickness and stiffness of the AC and UAB layers present a clearly significant impact on the maximum principal strain at the bottom of AC layer and the bulk stress in UAB, particularly during the summer season, whereas the thickness and stiffness of CTB and stiffness of subgrade have a minor impact. The responses of bulk stress and maximum principal strain can be empirically predicted by 2FI and Quadratic models. Optimal structure combinations (13.6 cm AC layer and 10 cm UAB) were recommended after quantifying the stress-dependent properties of UAB. The recommended structural combination has good fatigue resistance and can also efficiently minimize AC and UAB layer thickness.

To quantitatively characterize and evaluate the morphological features of coarse aggregate particles, 2D images of coarse aggregate particles were processed by using Image Pro-Plus software in this paper. Through image enhancement, correction, segmentation, and retrieval, six morphological indicators such as axial coefficient, rectangularity, roundness, roughness, angular parameters, and fractal dimension were obtained. Further statistical analysis of the distribution pattern of each morphological characteristic parameter was carried out in a large sample to provide a basis for the quality control of coarse aggregates processing. What’s more, further statistical analysis of the distribution pattern of each morphological characteristic parameter was carried out in a large sample to provide a basis for the quality control of coarse aggregates processing. The axial coefficient of coarse aggregates of different particle sizes, decreases with increasing particle size. The roundness decreases with increasing particle size, and the fractal dimension decreases with increasing particle size; the axial coefficient and rectangularity can be used to characterize the shape of coarse aggregates without the influence of angles. Roughness and fractal dimension can be used to characterize coarse aggregate angles independent of shape; angular parameters, roughness or angular parameters, and fractal dimension can be chosen when characterizing angles only. This study can provide a fast and efficient quantitative basis for the optimization of the coarse aggregate processing and process control of incoming quality.

In the context of the global pandemic of COVID-19, the use and disposal of medical masks have created a series of ethical and environmental issues. The purpose of this paper is to study and evaluate the high temperature properties and thermal storage stability of discarded-mask (DM)-modified asphalt from a multi-scale perspective using molecular dynamics (MD) simulation and experimental methods. A series of tests was conducted to evaluate the physical, rheological, thermal storage stability and microscopic properties of the samples. These tests include softening point, rotational viscosity, dynamic shear rheology (DSR), Fourier transform infrared (FT-IR) spectroscopy and molecular dynamics simulation. The results showed that the DM modifier could improve the softening point, rotational viscosity and rutting factor of the asphalt. After thermal storage, the DM-modified asphalt produced segregation. The difference in the softening point between the top and bottom of the sample increased from 2.2 °C to 17.1 °C when the DM modifier admixture was increased from 1% to 4%. FT-IR test results showed that the main component of the DM modifier was polypropylene, and the DM-modified asphalt was mainly a physical co-blending process. MD simulation results show that the DM modifier can increase the cohesive energy density (CED) and reduce the fractional free volume (FFV) of asphalt and reduce the binding energy between base asphalt and DM modifier. Multi-scale characterization reveals that DM modifiers can improve the high temperature performance and reduce the thermal storage stability of asphalt. It is noteworthy that both macroscopic tests and microscopic simulations show that 1% is an acceptable dosage level.