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Large macroporous structures of permeable asphalt pavement made high-viscosity asphalt (HVA) more susceptible to aging and failure. However, the standard pressure aging vessel (PAV) test was difficult to accurately emulate the long-term aging behavior of HVA. Hence, 1–5PAV aging levels of two HVAs (i.e. HVA-1 and HVA-2) were emulated by the simple aging test (SAT). Rheological analysis indicated that asphalt oxidation consistently dominated regardless of the long-term aging levels of HVAs. Combined with the fluorescence microscopy observation, HVA-2 with meticulous and uniform granular distribution was more resistant to aging than HVA-1 with coarse and continuously strip-like structures. Stress-strain curve analysis in linear amplitude sweep (LAS) test revealed that the accumulated strain energy (ASE) representing the overall mechanical properties of HVAs first increased and then decreased as the long-term aging level grew. The continuous repeated LAS (RLAS) test further reflected that the yield stress, yield strain and ASE of HVAs gradually decreased as the LAS loading number increased at initial long-term aging states; but as the sustained growth of aging level, the stress-strain curve of HVAs become increasingly chaotic until remarkable strain hardening occurred. Furthermore, RLAS-based self-healing (RLASSH) test was developed by introducing intermittent time into RLAS test. The variation of ratio of ASE decrease can characterize the self-healing performance of HVAs. RLASSH test showed that the self-healing performance of HVAs was unstable at 1–3PAV aging level, and the HVAs with 4 or 5PAV aging levels completely lost their self-healing performance. Overall, with the increase in long-term aging levels, significant differences were observed in the evolution characteristics of morphology, rheology and self-healing performances of different HVAs. This study helps to understand the rheology and self-healing performance evolution pattern of HVA during long-term service. • Performance evolution of various HVAs was totally different as long-term aging deepened. • Asphalt oxidation consistently dominated regardless of long-term aging levels of HVAs. • Stress-strain curve of HVAs become increasingly chaotic until remarkable strain hardening occurred as aging deepened. • Specific long-term thermal aging level was beneficial for HVA self-healing. [ABSTRACT FROM AUTHOR]

• The high fatigue damage dramatically reduces the low temperature healing potential of asphalt mixtures. • The internal crack distribution characteristics of different mixtures are different under the same fatigue degree. • The longer the intermittent time, the less the effect on fatigue healing of asphalt mixture. The primary objective of this study is to advance the understanding of the low temperature self-healing character of asphalt mixtures under different damage degrees, thus to determine the effective strategy of asphalt pavement maintenance. Firstly, three kinds of asphalt mixtures are selected to conduct the indirect tensile (IDT) fatigue test to a certain fatigue damage degree at low temperatures, and then the resilient modulus (Mr) at different rest time is measured to quantify the healing potential. Next, the fatigue loading with different intermittent time (0 s, 1 s and 3 s) is applied to determine the impact of intermittent time on healing potential. The results indicate that the descending order of healing potential of asphalt mixtures is: SMA-11 > AC-8 > AC-11 at 5 °C and −5°C. The loading intermittent time has an obvious effect on the fatigue damage state of asphalt mixtures, while the longer the intermittent time, the less the effect on fatigue damage healing. Besides, the fatigue damage state has great influence on its healing potential of asphalt mixture. Under the low damage conditions, the initial healing rate is greater than the long term healing rate. However, the low temperature (−5°C) dramatically reduces the healing rate of asphalt mixtures, and causes their long-term healing rate to stabilize gradually to a very low level. Especially under the high fatigue damage conditions, the healing potential of asphalt mixtures will almost disappear at −5°C. Furthermore, together with meso-scale Computed Tomography (CT) scanning technique, it is found that the internal crack distribution characteristics of different graded asphalt mixtures are different even under the same damage degree, which may explain the differences in the healing potential of asphalt mixtures. The use of a fast two-dimensional (2D) scanning technology further confirms that the crack zones inside the asphalt mixture are gradually shrinking after a period of high temperature healing. Finally, the Grey relational analysis reveals that the healing time has the most significant influence on the healing potential of asphalt mixtures. The gradation type and temperature have the similar influence level on the healing potential. The correlation degree between the fatigue damage degree and healing potential is the smallest compared with the other three factors. [ABSTRACT FROM AUTHOR]

Self-healing has great potential to extend the service life of asphalt pavement, and this capability has been regarded as an important strategy when designing a sustainable infrastructure. This review presents a comprehensive summary of the state-of-the-art investigations concerning the self-healing mechanism, model, characterization and enhancement, ranging from asphalt to asphalt pavement. Firstly, the self-healing phenomenon as a general concept in asphalt materials is analyzed including its definition and the differences among self-healing and some viscoelastic responses. Additionally, the development of self-healing in asphalt pavement design is introduced. Next, four kinds of possible self-healing mechanism and corresponding models are presented. It is pointed out that the continuum thermodynamic model, considering the whole process from damage initiation to healing recovery, can be a promising study field. Further, a set of self-healing multiscale characterization methods from microscale to macroscale as well as computational simulation scale, are summed up. Thereinto, the computational simulation shows great potential in simulating the self-healing behavior of asphalt materials from mechanical and molecular level. Moreover, the factors influencing self-healing capability are discussed, but the action mechanisms of some factors remain unclear and need to be investigated. Finally, two extrinsic self-healing technologies, induction heating and capsule healing, are recommended as preventive maintenance applications in asphalt pavement. In future, more effective energy-based healing systems or novel material-based healing systems are expected to be developed towards designing sustainable long-life asphalt pavement. [ABSTRACT FROM AUTHOR]

This paper systematically investigated the roles of aging and bio-oil regeneration on the self-healing evolution behavior of pure asphalt and terminal blend (TB) rubberized asphalt within wide temperature range, which was expected to promote the applications of self-healing asphalt pavement, meanwhile to accelerate the sustainable disposal of local bio-oil and rubber wastes. The self-healing, flow and elastic recovery (ER) abilities of asphalts within wide temperature range and their relationship were traced through the dynamic shear rheometer based fatigue-healing-fatigue, frequency sweep and creep recovery tests. Results revealed that different effects of temperature on ER and flow abilities of aged or rejuvenated asphalts resulted in the complexity of self-healing evolution behavior. The proposed ER-flow self-healing theory clarified that the ER ability of aged asphalts led the self-healing process in viscoelastic region, and the flow ability dominated as temperature rose into viscous flow region; however, the flow ability of regenerated asphalts dominated the self-healing at all measured temperatures. The aging growth percentage and regeneration recovery percentage (%RR) based on four self-healing characteristic temperatures were proposed to quantify the influences of aging and regeneration on self-healing evolution behavior of asphalts. The climate aging imparted severer impact on the self-healing evolution behavior of pure asphalt than long-term aging, whereas caused less impact on that of TB asphalt. The aging impact on the self-healing evolution behavior of TB asphalt was smaller than that of pure asphalt. Inversely, the %RR of rejuvenated asphalts increased as the growth of bio-oil content, and reached the maximum when adding 4%wt. waste cooking oil residues. The bio-oil elicited the greater regeneration improvement of self-healing performance than petroleum-based rejuvenator. Overall, the bio-oil regeneration recovery of the self-healing evolution performance of aged asphalts was limited. [Display omitted] • The elastic recovery(ER)-flow self-healing theory was proposed and clarified. • ER of aged asphalts led self-healing in viscoelastic region, while flow dominated in viscous flow region. • Flow ability of regenerated asphalts dominated self-healing at all measured temperatures. • Regeneration recovery percentage based on four self-healing characteristic temperatures was proposed. • Bio-oil regeneration recovery of aged asphalts in self-healing evolution performance was limited. [ABSTRACT FROM AUTHOR]

• The various applications of GPC in asphalt materials were summarized. • The basic principle, test methods and data analysis of GPC test were introduced. • The effects of experimental parameters on the GPC results were discussed. • Suggestions for future application of GPC in asphalt materials were proposed. Understanding the link between molecular composition and macro-mechanical performance of asphalt binder is crucial for the selection, modification and performance prediction of asphalt binder. As one of the chemical analysis technologies, gel permeation chromatography (GPC) provides an efficient and accurate approach to separate asphalt molecules based on the size difference. This review summarized the application of GPC in characterizing asphalt materials. The basic principle, test methods and data analysis were introduced firstly. Then the applications of GPC in asphalt materials in terms of fraction detection, modification process characterization, aging characterization, recycled asphalt evaluation, and performance prediction were systematically reviewed. Finally, several suggestions were made for the future application of GPC technology in asphalt material analysis. This review potentially provides a guide for researchers to understand the performance of asphalt binders from the perspective of molecular weight distribution, and further promotes the development of renewable, sustainable and durable asphalt materials for pavement construction and rehabilitation. [ABSTRACT FROM AUTHOR]

• At 30 °C weathering aging temperature, the deteriorated rheological properties of HVMA are mainly due to solar radiation. • At 50 °C weathering aging temperature, the thermal aging effect begins to appear under the stimulation of solar radiation. • At 70 °C weathering aging temperature, HVMA has suffered a severe weathering coupling aging. • The weathering aging rate of HVMA is fast initially and then slows down after 2 d aging. High viscosity modified asphalt (HVMA) is widely used as the binder for permeable asphalt pavement. The service life of permeable asphalt pavement strongly depends on the weathering aging resistance of HVMA due to the large porosity of permeable asphalt pavement. In order to investigate the accelerated deterioration effect of temperature on the weathering aging process, a laboratory accelerated weathering aging tester was used to simulate the long-term weathering aging of HVMA at different aging temperatures (30 °C, 50 °C, and 70 °C) and different weathering aging days (0 ~ 12d). A series of rheological tests were conducted to study the influence of weathering aging temperature on the rheological properties of HVMA. Then, FTIR test was applied to characterize the changes in chemical composition of HVMA at different weathering aging temperatures. Furthermore, an aging kinetics model was put forward to further understand the effect of aging temperature on the weathering aging rate of HVMA. The results indicate that the weathering aging rate of HVMA is fast in the early aging stage (0 ~ 2d) and slows down in the later aging stage (2 ~ 12d). The increase of aging temperature has a significant accelerated deterioration effect on the chemo-rheological properties of HVMA during weathering aging process. At 30 °C aging temperature, the deteriorated rheological properties of HVMA are mainly due to the aging of solar radiation. As the aging temperature increases to 50 °C, the thermal aging effect of HVMA begins to appear under the stimulation of solar radiation. When the aging temperature rises to 70 °C, HVMA has suffered from a severe coupled aging of high temperature, solar radiation and humidity. This coupled aging effect leads to a significant asphalt oxidation and polymer degradation, which is the main reason for the severely deteriorated rheological properties of HVMA. The proposed aging kinetics model results also confirm the accelerated deterioration effect of temperature during weathering aging process. [ABSTRACT FROM AUTHOR]

• The thermal aging of high viscosity modified asphalt consists of three processes: polymer degradation, phase structure damage and asphalt oxidation. • In short-term aging, the degradation of polymer has a more pronounced effect on the property of high viscosity modified asphalt. • In long-term aging, the oxidation of asphalt is dominated for the property change of high viscosity modified asphalt. • High viscosity modified asphalt has a better aging resistance than PEN70 asphalt and SBS modified asphalt. Currently, the high viscosity modified asphalt (HVMA) is widely used in the porous asphalt pavement (PA) in China. HVMA provides good raveling resistance and rutting resistance for PA due to the excellent rheological property of it. However, the high construction temperature and the well-developed void structure of PA lead to a severe aging of HVMA. In order to understand the thermal aging behavior and mechanism of HVMA, the changes of rheological property, chemical composition, and phase morphology of HVMA, SBS modified asphalt (SBSMA) and PEN70 asphalt (70#A) during thermal aging process were investigated in this study. Rotational viscosity (RV) test, frequency sweep test, and multiple stress creep recovery (MSCR) test were used to evaluate the rheological property of HVMA. Then, Fourier transform infrared spectroscopy (FTIR) test and Gel permeation chromatography (GPC) test were used to determine the effect of thermal aging on the chemical composition of HVMA. Moreover, the phase morphology of HVMA, and SBSMA were observed by Fluorescence microscopic (FM) test. Test results indicate that the rotational viscosity, softening point, and strain recovery of HVMA show a decreasing trend initially and then increase with the process of thermal aging. The polymer phase structure of HVMA degrades obviously in short-term aging process, which leads to a deteriorated rheological property of HVMA. After long-term aging, the oxidation of base asphalt is the main reason for the changes in rheological property of HVMA. The aging resistance of HVMA is better than 70#A and SBSMA. As the amount of polymers increases, the aging resistance of HVMA is further improved. During thermal aging process, the polymer phase structure of HVMA is more abundant than SBSMA, which contributes to the superior anti-aging property of HVMA. [ABSTRACT FROM AUTHOR]

[Display omitted] • UV–vis spectroscopy is an effective technique for the selection of anti-aging materials. • Anti-aging materials with distinct functionalities demonstrate mutual promotion and synergistic enhancement effects. • The TOPSIS method was employed to determine the optimal anti-weather aging combination. • The combined use of UV531, NanoTiO 2 , Irganox1010, and Irgafos168 can maximize resistance to weather aging. • The synergistic effect of UV531 and NanoTiO 2 is also quite favorable. Novel materials with anti-aging functionality play a crucial role in delaying the aging process and extending the service life of asphalt pavement. The objective of this study is to employ an improved mathematical TOPSIS method to optimize the best anti-weather aging combination for high-content polymer modified asphalt (SHCPMA). Firstly, the selection of light-absorbing materials, light-shielding materials, and antioxidants was conducted based on UV–vis spectroscopy test, resulting in eight unique anti-aging combination schemes. Then, an accelerated weather aging test was performed on SHCPMA to simulate its long-term outdoor aging process. Subsequently, a comprehensive investigation of the macro-rheological properties and micro-chemical properties of SHCPMA was carried out using rheological tests, Fourier transform infrared spectroscopy test, and gel permeation chromatography test. Finally, a comprehensive analysis was conducted using TOPSIS method to determine the optimal anti-weather aging combination. The results showed that UV531, NanoTiO 2 , Irganox1010 + Irgafos168 were the preferred light-absorbing, light-shielding, and antioxidant materials, respectively. These three types of anti-aging materials can effectively absorb solar radiation, shield solar radiation, and neutralize free radicals, thereby inhibiting the formation of polar oxygen-containing functional groups, and the degradation of polymer molecules during weather aging. The improved TOPSIS method indicated the combined use of three types of anti-aging materials can maximize SHCPMA's resistance to weather aging, and the synergistic effect of light-absorbing material and light-shielding material was also ideal in terms of anti-aging performance. The optimization of anti-aging materials contributes to prolonging the road service life, thereby promoting sustainable development in pavement engineering. [ABSTRACT FROM AUTHOR]

Waste cooking oil has surfaced as a hazardous waste that induces severe environmental contamination. Encapsulation technology presents a viable solution to regenerate the waste oil and augment the self-healing ability of asphalt materials. This study characterized capsules synthesized with selected waste oil for self-healing asphalt mixture, and evaluated the self-healing and environmental impact. The wetting ability, capillary, anti-aging, and self-healing performance of three potential healing agents were analyzed, and the optimal healing agent was obtained by evaluating the comprehensive behavior with the radar chart method. Capsules were synthesized using the ionic gelation method, and their thermal stability, chemical structure, mechanical performance, and morphology were characterized. Fatigue-healing performance asphalt mixture with capsules were investigated by indirect tensile fatigue test with intermittent time. Leakage of waste oil core were measure to verify it environmental impact to surroundings. Results showed that all healing agents could restore the aged asphalt, and waste rapeseed oil had superior overall performance with comprehensive f i value of 0.993 in radar chart evaluation. The compression characteristic of the capsules could transform from brittleness to plasticity as the water-to-oil(WO) ratio decreases from 15 to 5. SEM observation implied when the WO ratio varied from 10 to 15, the multi-pore structure of capsules could be appropriately filled. The addition of capsules in the mixture increased the fatigue life extension rate (HD f) of aged mixtures (with intermittent time 0.1 s∼0.8 s) by 10∼30%. Leakage of waste oil from the mixture was inhibited, substantially reducing 38% release of waste oil. This can serve as a means for the sustainable utilization of waste oil, thereby mitigating environmental pollution and negative effects caused by waste oil. [Display omitted] • Waste cooking oil was encapsulated in capsules for self-healing of asphalt mixture. • Waste cooking oil was optimized based on radar chart method. • Capsules were measured through thermal, mechanical and morphologic methods. • Addition of capsules in mixtures reduced the release of waste oil in water. [ABSTRACT FROM AUTHOR]

Highlights • The volume ratio of core materials (rejuvenator) to microcapsule reached 95%. • Microcapsules containing rejuvenator can survive during mixing and be broken during loading. • Microcapsules restore rheological properties of aged asphalt binder and prolong its fatigue life. • The healing efficiency of aged asphalt binder is proportional to the content of microcapsules. Abstract The microencapsulated rejuvenator within asphalt is a promising alternative approach to prolong the service life of asphalt pavement. The aim of this paper is to investigate the aided regeneration system of aged asphalt binder based on microcapsule technology. The microcapsules containing rejuvenator were fabricated by in-situ polymerization method, and the capsule shell was made of melamine-urea-formaldehyde (MUF) resin. Firstly, the micro-morphology of microcapsules was characterized by scanning electron microscope (SEM). It could be found that the volume ratio of the core materials (rejuvenator) to microcapsule reached to 95%. Further, the time sweep fatigue test together with fluorescence microscope (FM) was employed to study the rupture behavior of microcapsules in aged asphalt binder before and after loading. The test results indicated that the microcapsules had sufficient thermal stability and strength to suffer from mechanical agitation at a high temperature. In addition, the rejuvenator released from microcapsules partially restored complex shear modulus and phase angle of aged asphalt binder thus extended its fatigue life. Finally, the fatigue-rest-fatigue test using dynamic shear rheometer (DSR) was conducted to study the effect of microcapsules on the fatigue resistance and healing capacity of aged asphalt binder. The test results showed that the fatigue resistance of aged asphalt binder was enhanced by microcapsules containing rejuvenator and the fatigue life of aged asphalt binder with 1 wt% microcapsules was 45.68% higher than that of non-aged neat asphalt binder. Moreover, the microcapsules could improve the healing capacity of aged asphalt binder, and its healing efficiency was proportional to the content of microcapsules. [ABSTRACT FROM AUTHOR]

Asphalt aging and fatigue cracking are common forms of distresses in flexible pavements. Microencapsulated rejuvenator has been generating significant interest in the feasibility and potentiality applications of asphalt materials self-healing over the past decade and is likely to remain so for the foreseeable future. Despite multiple attempts, the prerequisite is crack propagation through the microcapsules and resulting in the broken shell, which is a passive release. Strategies toward self-healing of uncracked aged asphalt by microcapsules remain a significant challenge. Herein, numerous successful applications of controlled release microcapsules in other fields, including biomedical engineering, food industry, agriculture, smart coating, textile industry, and cosmetics, are classified and referenced. Special attention is given to the mechanisms of release and their triggers, followed by recent advances of microencapsulation technologies with detailed experimental demonstrations. In particular, the challenges and promising solutions of novel controlled release systems for asphalt materials are proposed in detail for the first time. This review aims to present future directions for research in this field, which provides new ideas for the smart maintenance of asphalt pavements. [ABSTRACT FROM AUTHOR]

As the main source of traffic noise, tire-pavement noise poses a major threat to human health. Reducing tire-pavement noise influences of quality of life has recently drawn increasing attention. Quiet asphalt pavement provides an effective method to reduce tire-pavement noise and achieves economic, social and environmental benefits, due to take advantage of the existing infrastructure and combines the function of reducing noise. Tire-pavement noise generation mechanisms, tire-pavement noise measurement methods, the noise reduction mechanism of pavement, and some common and novel quiet asphalt pavement are reviewed in this paper. The paper reveals that tire air-pumping noise is the main source of tire-pavement noise. The existing tire-pavement noise measurement methods need to be further perfected to improve the accuracy of measurement results. All quiet asphalt pavements have good noise reduction performance, but each has its suitable range of applications. The purpose of this review is to provide reference and guidance for researchers to measure the tire-pavement noise, design quiet asphalt pavement, and select suitable quiet pavement according to the local conditions. [ABSTRACT FROM AUTHOR]

• The strain recovery of HVMA decreased initially and then increased with the process of weathering aging. • HVMA showed a slight decrease in fatigue resistance at 50° C weathering aging. • HVMA showed a significant decrease in fatigue resistance at 70° C weathering aging. • The fatigue resistance of HVMA was related to polymer structures, asphaltene content, and surface microcracks. Currently, high viscosity modified asphalt (HVMA) has broad application prospects in permeable asphalt pavement. However, the large-void structure of permeable asphalt pavement makes HVMA excessively exposed to extremely adverse coupling aging of solar radiation, heat, and moisture, which accelerates the performance deterioration of HVMA. In order to investigate the effect of weathering aging on the permanent deformation and fatigue resistance of HVMA during the long-term service period, an accelerated weathering aging tester considering solar radiation, heat, and moisture was used in this study to simulate different weathering aging environment. Dynamic shear rheometer and multiple stress creep recovery test were conducted to investigate the high-temperature rheology property of HVMA at different weathering aging stages. Linear amplitude sweep test was applied to evaluate the effect of weathering aging on the fatigue resistance of HVMA. Besides, gel permeation chromatography test and fluorescence microscopic observation were used to study the molecular weight distribution and surface micromorphology of HVMA during weathering aging, respectively. The results showed that the effect of weathering aging led to an increasing rutting factor and a decreasing non-recoverable creep compliance of HVMA. The strain recovery of HVMA decreased initially and then increased with the process of weathering aging. At 50 °C weathering aging condition, the decrease in the fatigue resistance of HVMA was not significant. However, the fatigue resistance of HVMA showed a significantly decreasing trend with the process of 70 °C weathering aging. After 12d of 70 °C weathering aging, the N f 2.5% (fatigue life at 2.5% strain) of HVMA decreased from 455,035 cycle numbers to 1908 cycle numbers sharply. The degradation of polymers, the increase of asphaltene content, and the extension of surface microcracks were the main reasons for the deteriorated fatigue resistance of HVMA after long-term weathering aging. [ABSTRACT FROM AUTHOR]