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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]

Due to the excellent shear deformation resistance of high-viscosity polymer-modified bitumen (HVPMB), the traditional methods based on time sweep and linear amplitude sweep (LAS) had problems with insufficient damage accumulation and inability to disrupt the integrity of HVPMB, making it difficult to accurately evaluate its fatigue and healing characteristics. To solve this problem, this study developed an effective evaluation proposal called continuous multiple LAS (MLAS) test and MLAS-based healing (MLASH) test. One base bitumen and three HVPMBs were selected for related experiments. MLAS test results confirmed that the percentage of strain energy attenuation (PSEA) can be used to evaluate the fatigue damage degree of HVPMBs. The lower the PSEA , the lesser damage. Combined with the fluorescence microscope and direct photography observation, the fatigue hairline cracks during MLAS test gradually expanded from the sample periphery to center until completely destroyed. Further, the MLASH test was developed to evaluate the healing performance of HVPMB by introducing intermittent duration into MLAS test. The variation of PSEA after tenth LAS loading (i.e. Δ PSEA) was proposed to evaluate the healing performance of HVPMB. The larger the Δ PSEA , the better the healing performance of HVPMB. All HVPMBs showed satisfactory healing performance once there was sufficient healing intermittent time (e.g. 180 s), and the healing performance was negatively correlated with the damage degree. Notably, the polymer structures had a dual effect on the healing performance of HVPMB, that is, they promoted the elastic healing recovery of HVPMB at lower temperature, while hindering the flow healing recovery at higher temperatures. Moreover, different temperatures caused a shift in the ranking of healing performance of various HVPMBs, thus the healing result at only single temperature cannot comprehensively represent the healing performance of HVPMB. Overall, the newly developed evaluation proposal can help to select HVPMB with excellent fatigue resistance and healing properties and provide a certain basis for accurately predicting HVPMB pavement life. [Display omitted] ● An effective evaluation proposal based on MLAS was developed. ● Percentage of strain energy attenuation (PSEA) can evaluate the fatigue degree of HVPMB. ● Variation of PSEA after tenth LAS loading can evaluate the healing performance of HVPMB. ● Polymer structures had a dual effect on the healing performance of HVPMB. ● Healing result at only single temperature cannot comprehensively represented the healing performance of HVPMB. [ABSTRACT FROM AUTHOR]

High-viscosity asphalt (HVA) provides excellent cracking and rutting resistance for ecological permeable pavement. However, HVA suffers from severe aging due to higher construction temperatures and rich porous structures, which limited its applications for urban sustainability. Currently there is still a lack of knowledge about the thermal aging effects and mechanisms of HVA. In this study, the effects of thermal aging on the morphological structures, rheological and fatigue properties of two HVAs (i.e. HVA-1 and HVA-2) at five aging levels via Simple Aging Test (SAT) are systematically investigated. HVA-1, characterized by loosen and coarse reticulated structures, undergoes significant structural changes during aging, whereas HVA-2, characterized by dense and fine reticulated structures, experiences fewer alterations. The changes in the modulus master curves of HVAs become more gradual after aging, indicating the reduced temperature sensitivity. Multiple stress creep recovery results reflect that two types of HVAs exhibit totally different dominance of oxidation or polymer degradation depending on aging level. Liner amplitude sweep (LAS) results based on damage mechanics analysis reveal that aging leads to an increase in the accumulated strain energy observed in stress-strain curves for both HVAs. As aging progresses, the proportion of elastic energy decreases due to polymer degradation, resulting in a reduction in fatigue life. Especially, the fatigue life of aged HVAs significantly decreases after SAT40. LAS results based on fracture mechanics analysis show that the crack length increases with aging due to polymer degradation and asphalt phase hardening. Aging effect on crack length was limited at initial stage but becomes more significant as crack extends. As aging deepens, the crack initial stage of HVAs tends to lengthen while the crack extension stage tends to shorten. Moreover, the crack growth process of HVAs follows a two-stage behavior of crack initiation and propagation under certain aging levels from the relationship between energy release rate and crack propagation rate. Overall, the thermal aging kinetics of various HVAs differ significantly in the structures, rheological and fatigue properties as aging deepens. HVA-2 with loosen and coarse structures exhibits greater aging resistance and lower temperature sensitivity than HVA-1 with dense and fine structures. • Different HVAs exhibits totally various dominance of oxidation or polymer degradation depending on aging level. • Fatigue life of aged HVAs significantly decreases after SAT40. • Aging effects become more significant as crack extends. • Crack growth process of HVAs follows a two-stage behavior of crack initiation and propagation. • Thermal aging kinetics of various HVAs differ significantly. [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]

In order to distinguish the wetting healing stage and the molecular diffusion healing stage during the self-healing process of asphalt binders, the fluorescence microscope (FM) together with the image processing technique was employed. The healing index was put forward based on the variation of crack area. On the basis of the established capillary diffusion theory, the Two-Stage Model was built to fit the healing curves characterizing the healing index variation with healing time. It is found that the established method is quite suitable to identify the wetting and the diffusion stages. The wetting healing occurs firstly, during which the asphalt molecules spontaneously wet the both faces of crack. Although the strength recovery is not distinct at this stage, SBS modified asphalt shows greater wetting healing strength than the other neat asphalt binders. Once the wetting process is nearly finished, the molecular diffusion healing ratio accelerates significantly, and the descending order of the molecular diffusion rate is: SBS > PEN 100 > PEN 70 > PEN 50 > PEN 20. The test results also show that the disappearance of visible crack does not indicate that the strength has been fully recovered. Here, the tensile strength test is developed to identify the strength recovery rate after the crack is fully closed, which implies that the strength regeneration is a long process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Decay pattern of self-healing temperature susceptibility of bitumens at various ageing states is examined. • Self-healing rate parabola evolution with temperature of bitumen is related to the frequent phase transition. • Superposition impacts of temperature and ageing on phase structures elicit the healing transition phenomena. • All-weather ageing causes more serious impact on self-healing temperature susceptibility than long-term ageing. • RA bitumen undergoes smaller ageing impact on self-healing temperature susceptibility than pure bitumen. Understanding the evolution law of the self-healing ability of bitumen under actual service environment is conductive to optimizing the design of self-healing bituminous pavement, while the changing temperatures and variety of ageing states complicate this issue. In this study, the decay pattern of self-healing temperature susceptibility of pure bitumen and rock-asphalt (RA) modified bitumen at the simulated ageing states of thermal oxidation and all-weather is analyzed by the dynamic shear rheometer based fatigue-healing-fatigue experiment. Through the thin layer chromatography, differential scanning calorimeter and rheological characterizations, the chemical composition, colloidal stability and macro phase transition (PT) behavior of bitumens with various ageing levels are examined. Results show that the self-healing rate parabola evolution with temperature of bitumen has to do with its frequent PT behaviors. The shift of self-healing curves and the appearance of healing inert temperature zone are the results of the growth of heavy components and decays of colloidal structure and phase structure caused by ageing. Notably, the superposition impacts of temperature and ageing on bitumen phase structures elicit the healing transition phenomena in the viscoelastic zone and viscous flow zone. Moreover, the multi-scale analysis reveals that the decay of self-healing temperature susceptibility with ageing is consistent with the deterioration tendency of the macro PT property, chemical composition and colloidal stability. Especially, all-weather ageing causes more serious impact on the self-healing temperature susceptibility of bitumens than thermal oxidative long-term ageing. RA bitumen with greater ageing resistance undergoes smaller ageing impact on self-healing temperature susceptibility than pure bitumen. [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 survival rate of microcapsules during mixing and compaction of asphalt mixture was measured. • The survival rate of microcapsules could be improved by reducing the microcapsule size and the mixing temperature. • The bigger microcapsules were more easily activated by the stress at the crack tip. • It is suggested that the size of MUF microcapsules should be controlled within 15 μm ~ 25 μm. Microcapsule technology exhibits great potential in improving the healing efficiency of asphalt mixture and prolonging the service life of the pavement. The capsule should be kept intact in the mixing and compaction process of asphalt mixture, whereas broken to release the healing agents in time when cracks encounter it. This paper aims to investigate the survival and activation behavior of microcapsules in asphalt mixture during construction and service period. By means of the in situ polymerization method, the microcapsules of various sizes were prepared and their particle size distribution, core material content, shell permeability, and other properties were characterized. Based on the quantitative analysis principle of Fourier transform infrared spectrometer (FTIR), the influence of microcapsule size and mixing temperature on the survival rate of microcapsules was analyzed. Meanwhile, the morphology and size distribution of surviving microcapsules was obtained via fluorescence microscope (FM). In addition, the morphologies of microcapsules before and after the bitumen bond strength (BBS) test and dynamic shear rheological (DSR) test were observed by FM to examine the releasing behavior of microcapsules. Finally, the fatigue-rest-fatigue test was performed to investigate the influence of microcapsule size on the healing efficiency of aged asphalt mastic. The results showed that the survival rate could be improved by reducing the construction temperature and the microcapsules size. The loss of microcapsules was more likely to happen in the mixing process rather than in the compaction process. Microcapsules with larger sizes were easier to be activated to remarkably enhance the healing efficiency of the aged asphalt mastic. Notably, the microcapsules with appropriate size are recommended to be added to the mixtures to ensure that the microcapsules survive in the construction process and are activated when cracks appeared. [ABSTRACT FROM AUTHOR]

• Key preparation parameters were optimized using an orthogonal test. • Waste cooking oil residue improved the low-temperature performance of rubber asphalt. • Waste cooking oil residue enhanced the storage stability of rubber asphalt. • Waste cooking oil residue improved the aging resistance of rubber asphalt. The poor storage stability of rubber asphalt induced by the incompatibility of the rubber-asphalt system still remains challenging although extensive researches have been performed. In this study, the waste cooking oil residue (WCOR) was used as a stabilizer to prepare a hot storage-stable rubber asphalt (HSSRA). The key preparation parameters in terms of WCOR content, mixing temperature and mixing time were optimized using an orthogonal test, and the resulting softening point difference value of HSSRA reached 0.3 ℃ at the optimum preparation condition. Chemical and molecular analysis via Fourier transform infrared (FTIR) spectroscopy and gel permeation chromatography (GPC), as well as phase morphology analysis via fluorescence microscopy (FM) showed that there was no chemical reaction between WCOR and rubber particles during the preparation process. The incorporation of WCOR in rubber asphalt promoted the swelling and decomposition of rubber particles, which led to the improved storage stability of HSSRA. Brookfield viscosity analysis proved that WCOR reduced the viscosity of HSSRA, thus lowering the mixing and compaction temperature. Rheological characterization via dynamic shear rheometer (DSR) and bending beam rheometer (BBR) revealed that the low-temperature performance of HSSRA was enhanced significantly compared with that of rubber asphalt, whereas the high-temperature stability of HSSRA was slightly reduced. Notably, the aging resistance of HSSRA was improved due to the effect of WCOR. [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] • The recycling of aged HVMA was achieved using oil-based rejuvenators and polymer-based rejuvenators. • The environmental oxidation behavior and mechanism of rejuvenated HVMAs was investigated. • The polymer-based rejuvenated HVMAs exhibit superior resistance to environmental oxidation. • The polymer-based rejuvenators can restructure the polymer phase structures of aged HVMA. • The strongest antioxidative ability of SFO is attributed to its UV abosoprtion and free radical scavenging capacity. • WCO is susceptible to oxidation due to its significant amount of unsaturated fatty acid esters. The investigation of long-term environmental oxidation resistance of rejuvenated high-viscosity modified asphalt (HVMA) is of great significance as it unlocks its full potential for recycled utilization, offering improved solutions for sustainable and cost-effective pavement infrastructure. This study aims to comprehensively investigate the long-term environmental oxidation resistance and mechanisms of various oil-based and polymer-based rejuvenated HVMAs. Firstly, the long-term oxidation process of oil-based and polymer-based rejuvenated HVMAs was simulated using the indoor accelerated environmental aging test. Subsequently, a series of rheological tests and X-ray photoelectron spectroscopy (XPS) test were employed to examine the environmental oxidation characterization of rejuvenated HVMAs. Finally, a radar chart was proposed to rank the anti-oxidation capabilities of various rejuvenated HVMAs, accompanied by a detailed oxidation mechanism analysis. The results indicate that polymer-based rejuvenated HVMA exhibits superior environmental oxidation resistance compared to oil-based rejuvenated HVMA. The addition of polymer-based rejuvenators effectively retards the phase angle plateau disappearance and rheological performance deterioration of rejuvenated HVMA during environmental aging. Polymer-based rejuvenators significantly slow down the oxidation rates of carbon and sulfur elements in rejuvenated HVMA. Although the addition of oil-based rejuvenators may not enhance the anti-oxidation capability, the restructuring of the polymer phase structure plays a crucial role in improving the anti-oxidation performance. The ranking of anti-oxidation capabilities among the four polymer-based rejuvenated HVMAs is as follows: SBS-based waste furfural oil (SFO) > SBS-based waste rubber oil (SRO) > SBS-based aromatic oil (SR) > SBS-based waste cooking oil (SWCO). SFO demonstrates the highest resistance to environmental oxidation, primarily attributed to the inherent UV absorption and free radical scavenging capability of furfural oil (FO). SRO exhibits favorable anti-aging performance due to the chemical composition resembling asphalt, which provides enhanced chemical stability. Conversely, waste cooking oil (WCO) contains a significant amount of unsaturated fatty acid esters, which is susceptible to oxidation due to oxygen attack, resulting in the lowest anti-aging capability of SWCO. [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]

[Display omitted] • It is studied if recycled oils can replace aromatic oil as compatibilizer of HVMA. • Recycled oils show greater rheological improvement on HVMA than aromatic oil. • Synergistic effect of PPA and sulfur have excellent modification role on HVMA. • Adding recycled oils alone does not improve storage stability of HVMA. • Combination of REO and chemical stabilizers greatly improves storage stability of HVMA. Using recycled oils and chemical stabilizers as the additives in high-viscosity modified asphalt (HVMA) is being developed as a sustainable way to solve the severe segregation problems due to the large differences in nature between high-content styrene–butadienestyrene (SBS) and base asphalt. This paper attempts to use three recycled oils, namely castor oil (CO), waste cooking oil (WCO) and recycled engine oil (REO), as compatibilizers in combination with different chemical stabilizers (polyphosphoric acid, PPA; sulfur) to investigate their ameliorative roles on HVMA segregation problems. By means of the gel permeation chromatography, dynamic shear rheometer and fluorescence microscopy, the chemo-rheological properties and morphological structures of HVMA are investigated, as well as their storage stability. Results show that the recycled oils are more favorable to improve the high-temperature rheological performance of HVMA than aromatic oil (AO) by comprehensively considering the softening point, zero-shear viscosity, elastic recovery percent and large molecule percentage, and the role ranking is: REO > WCO > CO > AO. Compared with the addition of PPA or sulfur alone, when PPA and sulfur are added together, the rheological performance of HVMA is promoted most significantly, because of the synergistic cross-linking reaction of these chemical stabilizers with asphalt and polymers. Furthermore, the synergistic effect of PPA and sulfur markedly reduces the temperature sensitivity of HVMA. However, the cigar tube test reflects that adding recycled oils as compatibilizers alone can not improve the storage stability of HVMA, and CO and WCO even aggravate its segregation. Notably, adding REO and chemical stabilizers can markedly improve the storage stability of HVMA, and the effect is most obvious when REO, PPA and sulfur are added together. [ABSTRACT FROM AUTHOR]

[Display omitted] • Burgers model and damage mechanics-based crack model are applicable for polymer modified asphalt (PMA) materials. • A two-stage crack growth model based on damage mechanics is proposed for PMA materials. • Recovery percentage and delayed elastic perform good correlation between PMA binders and mastics. • Fatigue life performs very significant correlation between PMA binders and mastics. Traditional evaluation parameters for multiple stress creep recovery (MSCR) test and linear amplitude sweep (LAS) test are difficult to deeply and theoretically characterize the high- and intermediate-temperature rheological behaviors of polymer modified asphalt (PMA) binders and mastics. In this paper, one neat asphalt and four types of PMA binders and mastics are selected (i.e., the rubber modified ones, SBS modified ones, thermoplastic elastomer modified ones and SBS/Rubber modified ones). Two new analysis methods, i.e. Burgers model and damage mechanics-based crack growth model, are applied in analyzing the high- and intermediate-temperature rheological behaviors of PMA materials respectively. The Burgers model results indicate adding filler decreases the viscous deformation, and leads to lower non-recoverable compliance in the MSCR test. The polymer modification transfers the delayed elastic deformation to elastic deformation, thus causing more excellent rutting resistance. The damage mechanics-based crack growth model analysis reveals that adding filler enhances the crack growth rate and crack length, thus sacrificing the fatigue resistance. By contrast, the polymer modification enhances the fatigue resistance regardless of polymer types. Notably, a two-stage pattern based on crack growth rate and energy release rate was further proposed to identify the crack initiation and propagation of PMA materials. Specifically, 30% rubber modified asphalt binders and mastics perform best in both rutting and fatigue resistance. Moreover, PMA binders and mastics have strong correlation based on the recovery percentage and delayed elastic deformation. The correlation of fatigue life between PMA binders and mastics is very significant, however there was no obvious correlation in terms of crack length. [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]

• Mohr-Coulomb failure criterion can be used to describe the behavior of pervious concrete. • With the decrease of the thickness of cement paste, the cohesion first increase, and then decrease slightly. • A modified mix design method based on Mohr-Coulomb failure criterion was proposed by introducing the aggregate content coefficient (ACC). Large porosity and connected porous structure enables pervious concrete to obtain water permeability, but significantly decreases its strength. It is still a critical challenge for the mix design of pervious concrete to well balance its permeability and strength. The purpose of this paper is to study the strength mechanism of pervious concrete and propose a modified mix design method based on Mohr-Coulomb failure criterion. Five groups of samples with different aggregate-cement ratio varied from 5:1 to 4:1 were prepared (target porosity was 20%). The triaxial tests were applied to investigate the axial compression of these pervious concrete samples at different confining pressure. The results show that Mohr-Coulomb failure criterion can be used to describe the behavior of pervious concrete with compression. With the decrease of the thickness of cement paste, the cohesion first increase, and then decrease slightly. At the same porosity, the cementitious paste thickness was largely determined by aggregate content coefficient (ACC). A modified mix design method based on Mohr-Coulomb failure criterion was put forward by introducing the aggregate content coefficient (ACC). It was observed that ACC had little influence on porosity, pore area and fractal dimension of pervious concrete, and pervious concrete with different ACC had similar permeability. The strength increased with the decrease of ACC , but the growth rate was gradually decreasing. For the case in this paper, 0.94 was found to be the optimal value for ACC. By the modified mix design method, pervious concrete gained a similar permeability but obviously improved strength compared to the pervious concrete designed by conventional method. [ABSTRACT FROM AUTHOR]

• Aged SBS modified asphalt was rejuvenated by different rejuvenation methods. • Fatigue resistance of aged binder can be well recovered by reactive rejuvenation. • Reactive rejuvenated binder shows good self-healing performance. Reclaimed bituminous mixture can be used in new pavement after rejuvenation. Common rejuvenation method and reactive rejuvenation method can be used to restore the properties of aged SBS modified asphalt(ASMB). This work focused on the recovery effect of fatigue resistance for ASMB by different rejuvenation methods. The effect of common and reactive rejuvenation on the fatigue behavior of ASMB was investigated by multi-stress creep and recovery test, linear amplitude sweep test and fatigue-healing-fatigue test. The results show that, as compared with common rejuvenation method, reactive rejuvenation method is more conducive to restoring the creep recovery rate and the non-recovered creep compliance of ASMB. Linear amplitude sweep test indicates that reactive rejuvenated ASMB shows the good fatigue stress cracking resistance, the fatigue life of which at 2.5% and 5.0% strain levels is increased by 30% and 71% as compared with that of common rejuvenated binder. Meanwhile, the self-healing index of reactive rejuvenated ASMB is also enhanced by 28.7%, which indicates its better self-healing potential and fatigue damage resistance. Furthermore, the fatigue life of SMB is reduced by 77.7% after aging, while that of ASMB is extended by 93.5% after common rejuvenation, and the fatigue life of reactive rejuvenated ASMB is almost twice than that of common rejuvenated binder. It means that reducing the adverse effects of aged asphalt and reconstructing the broken SBS cross-linking structure during rejuvenation process of ASMB are all crucial for restoring its fatigue resistance. [ABSTRACT FROM AUTHOR]

• The behavior of aging degradation and reactive reconstruction for SBS were studied. • The molecular weight of SBS decreased and its rheological properties deteriorated seriously after simulated aging. • The creep recovery ability and medium–high temperature rheological properties of aged SBS can be well restored by reactive reconstruction. • Isocyanate pre-polymer showed the better performance for restoring the molecular weight and the glass transition temperature of aged SBS. Achieving high-performance recycling of aged SBS modified asphalt will help promote the sustainable development of transportation infrastructure. The destruction of the SBS cross-linking network is an important reason for the deterioration of the performance of aged SBS modified asphalt. Scientific reconstruction of aged SBS cross-linked network is the key to achieving the performance recovery of aged modified asphalt. In this research, the evolution of chemical structure, molecular weight, thermodynamic properties, multiple stress creep recovery capability and rheological property of SBS during the process of aging degradation and reactive reconstruction were systematically investigated. The results showed that the molecular weight and creep recovery capability of SBS decreased sharply, and its complex modulus and phase angle exhibited a strong temperature and frequency dependence after aging. While the number average molecular weight of aged SBS increased by over 70% after reactive reconstruction, and its thermal-oxygen stability shown better performance as compared with that of fresh SBS. Meanwhile, the glass transition temperature of aged SBS was restored to −43.8℃ and −54.9℃ after reactive reconstructed by toluene diisocyanate (TDI) and isocyanate pre-polymer. Therefore, isocyanate pre-polymer with flexible long chain structure was more benefit for improving the low-temperature performance of reactive reconstructed aged SBS. Furthermore, the creep recovery ability and complex modulus of aged SBS were all significantly improved, and exhibited dramatically high-elastic properties after reactive reconstruction. And as compared with isocyanate pre-polymer, TDI with benzene ring rigid structure was more conducive to restoring the medium–high temperature rheological properties of aged SBS. Therefore, effective restoration of molecular weight and performance of aged SBS can be achieved by using reaction reconstruction method. This study would provide inspiration and ideas for the high-value recycling of waste polymer modified asphalt. [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]

[Display omitted] • Aromatic oil cannot solve the storage stability and compatibility issues of high-viscosity particle modified asphalt (HVPMA). • Stabilizers (PPA or sulfur) can significantly improve the storage stability and compatibility of HVPMA. • Rheological-based segregation index is more accurate for evaluating storage stability than softening point difference. • Cole-Cole plot analysis do not provide sufficient information predict the compatibility of HVPMA. High-viscosity particle modified asphalt (HVPMA) is one of the most popular asphalt binders for permeable pavement in China. This commercial high-viscosity particle modifier is usually rich in styrene–butadienestyrene (SBS) polymers, which brings marked storage stability and compatibility issues to HVPMA. Hence, this study aims to investigate the roles of aromatic oils (AO), polyphosphoric acid (PPA) and sulfur on the storage stability and compatibility of HVPMA. The effects of AO, PPA and sulfur on the overall performance of HVPMA are firstly investigated by physical, rheological tests and morphological observations. Through the cigar tube test, the effects of various additives on the storage stability of HVPMA are then analyzed. Lastly, the effects of various additives on the compatibility of HVPMA are determined by the Cole-Cole plot method via frequency scan test. Morphological observations indicate that the polymer phases become swelled and smoother after adding AO, and adding the chemical stabilizers can boost the formation of the network structures. The physical and rheological results show that the combination of PPA and sulfur makes the greatest contribution to the high-temperature performance improvement of HVPMA, followed by PPA and sulfur. Separation test results reflect that adding AO has little improvement on the storage stability of HVPMA, while the storage stability of HVPMA can be significantly improved by the addition of chemical stabilizers (i.e., PPA, sulfur, or a combination of both). The accuracy of the segregation index (SI) based on rheological properties is higher than that of the traditional softening point difference (SPD) index, and the SI value based on ZSV is easier to determine the segregation status. However, it is difficult to determine the correspondence between Cole-Cole curve symmetry and compatibility due to the influence of temperature, and the Cole-Cole curve method cannot provide sufficient information to determine the compatibility of HVPMA. [ABSTRACT FROM AUTHOR]

• The successful applications of depth‑sensing indentation on asphalt materials were reviewed. • The basic principle, analysis method and experimental key points of depth‑sensing indentation were summarized. • 'The challenges and suggestions of depth‑sensing indentation on the applications of asphalt materials were presented. • Prospect of depth‑sensing indentation were suggested. Depth‑sensing indentation is a powerful testing technology used to quantitatively characterize the mechanical properties of asphalt materials at different scales. Besides hardness and Young's modulus, rich micro mechanical properties such as adhesion and stiffness can also be obtained by the load-displacement curve from the depth‑sensing indentation. Furthermore, depth‑sensing indentation provides an efficient approach to investigate the mechanical properties of aggregate, asphalt binder, asphalt mastic, and interface zone (ITZ) without separating them from the asphalt mixture, which is of value for investigating the microstructure properties and building numerical models of asphalt mixture. In this review, the key theoretical and experimental procedure of depth‑sensing indentation are discussed, including basic principle, analysis method, sample preparation, and parameter selection. Moreover, the applications of depth‑sensing indentation in phase and ITZ identification, numerical models, aging, moisture susceptibility, and modifiers investigation of asphalt binder, mastic, and mixture are concluded in detail. The challenges for the applications of depth‑sensing indentation on asphalt materials are also presented with some suggestions for further development. [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]