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In order to address the issues of high viscosity and excessive fume exhaust associated with high-viscosity modified asphalt (HVMA), the objective of this study was to develop an eco-friendly HVMA by incorporating fume suppressants and viscosity-retarding agents (VRAs). To begin with, desulfurization rubber powder (DRP) was utilized as a modifier, and fume suppressants, including activated carbon, a chemical reaction fume suppressant, and a composite fume suppressant combining activated carbon and chemical reaction fume suppressant were added to the HVMA separately. The fume suppression effect and odor level were observed to determine the optimal fume suppressant composition for this study. Based on these observations, an area integration method was proposed, utilizing rotational viscosity testing and temperature sweeping experiments, evaluating the viscosity-retarding effect and mixing temperature when different amounts of Sasobit VRA, Evotherm3G VRA, and a composite VRA of Sasobit and Evotherm3G were added to the HVMA. This approach aimed to identify the eco-friendly HVMA with the most effective fume suppression and viscosity-retarding abilities. Furthermore, the morphology and rheological properties of the eco-friendly HVMA were examined through fluorescence microscopy, zero shear viscosity test, multiple stress creep recovery analysis, liner amplitude sweep test, and frequency sweep test. The results demonstrated that the HVMA formulation consisting of 15% DRP and 1% composite fume suppressant exhibited a satisfactory fume suppression effect and odor level. Based on this, the HVMA formulation containing 0.6% Evotherm3G and 3% Sasobit VRAs displayed the best viscosity-retarding effect while reducing the mixing temperature. Moreover, when compared to common HVMA, the eco-friendly HVMA exhibited excellent high-temperature resistance, successfully accomplishing the dual objectives of ecological friendliness and superior performance. [ABSTRACT FROM AUTHOR]

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]

Waste cooking oil residues (WCORs)-based bio-asphalt is a potential substitute for petroleum asphalt. However, asphalt binders with a high WCOR content indicates a low rheological property, leading to a limited WCOR mixed content (usually no more than 10 wt% of asphalt binder). This study aims to prepare an eco-friendly bio-asphalt with a high WCOR content. Based on the formula uniform design method, the optimum blending proportion of the bio-asphalt was determined as 33.3% WCOR, 31.8% hard asphalt particles (HAP), 30.3% hydrocarbon resin (HR 1 ), 4.6% recycled low density polyethylene (R-LDPE), and external 4% linear SBS polymer (L-SBS). Rheological test results indicated that the optimized bio-asphalt (OBA) presented similar high-temperature performance to SBS modified asphalt (SBS-MA), and much better low-temperature performance than both of SBS-MA and PEN 70 base asphalt (PEN 70). Fourier transform infrared spectroscopy (FTIR) test proved that OBA had some special chemical composition such as the acids and esters originated from the addition of WCOR. On the basis of mixture performance tests, it confirmed that OBA mixture possessed similar rutting resistance and moisture susceptibility to SBS-MA mixture, and showed more satisfying low-temperature capability than both of SBS-MA mixture and PEN 70 mixture. Additionally, OBA mixture showed prominent fatigue performance since it had the highest fatigue life and stable fatigue sensitivity at different strain levels. All above evaluations imply the feasibility of using high content of WCOR in road construction applications since OBA containing 33.3% WCOR shows excellent binder and mixture performance. [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]

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]

• Waste cooking oil residue can penetrate into ground tire rubber particle easily. • The swelling degree of rubber can be extended by waste cooking oil residue. • Rubber particle swelled by waste cooking oil residue tends to degrade into asphalt. • Pres-welled rubber contributes to the enhanced compatibility of rubber asphalt. • The component exchange between rubber particle and asphalt was elucidated. Bio oil was proved an effective modifier to improve the compatibility of rubber asphalt. However, the pathway in which the bio oil enhances the compatibility of rubber asphalt remains unclear. To understand the role of the bio oil in rubber asphalt during preparation process, the waste cooking oil residue (WCOR) was incorporated during the preparation of rubber asphalt in different scenarios. The compatibility of the prepared rubber asphalts was examined through the cigar tube test, the rheological characterization and the morphology observation. The compositional change of ground tire rubber (GTR) extracted from the prepared rubber asphalts was analyzed via the thermogravimetric analysis (TGA), and the chemical and fractional composition of the asphalt phase separated from the three rubber asphalts was analyzed via the Fourier transform infrared spectroscopy (FTIR) test and the thin-layer chromatography with flame ionization detection (TLC-FID) test. Results showed that the compatibility of the rubber asphalt with GTR swelled by WCOR prior to preparation was significantly improved compared with that of the rubber asphalt with untreated GTR and the rubber asphalt prepared by blending GTR and WCOR simultaneously. The results from chemical and compositional characterization suggested that the improved compatibility of the rubber asphalt incorporating GTR pre-swelled with WCOR was mainly attributed to the extended release of nature rubber (NR) and traces of synthetic rubber (SR) and inorganic filler into the asphalt phase. [ABSTRACT FROM AUTHOR]

Healing characteristics of asphalt lay a foundation for the wide applications of permanent roads. However, the decay pattern of asphalt healing ability in actual climate environments still remains unclear. Hence, the weather accelerated ageing (WAA) influence on the healing temperature sensitivity of several representative asphalts is systematically investigated in this paper. Results from fatigue-healing-fatigue (FHF) experiment show that the WAA and terminal blend crumb rubber (TBCR) modification impart pronounced impacts to the healing temperature sensitivity of asphalts. Notably, it is found that the aged asphalt has a healing inertia zone with low healing temperature sensitivity, in which the healing ability of asphalt is at a relatively low level. Furthermore, four kinds of various index temperatures are put forward as the evaluation indicators to quantitatively characterize the influence of WAA on the healing temperature sensitivity, i.e. inert extended temperature at healing rate curve, inert extended temperature at healing percentage curve, top healing temperature (THT) shift value and complete healing temperature range (CHTR) shift value. Moreover, the greater the WAA resistance of asphalt, the smaller the WAA influence on its healing temperature sensitivity. The WAA reduces the differences of healing temperature sensitivity among various asphalts. Lastly, the thermal stability and phase behavior investigations reveal that the molecular compositions and phase state transition (PST) of asphalt will be changed after WAA, eventually inducing the healing temperature shift and the appearance of healing inertia zone. Image 1 • Four index temperatures are proposed to evaluate the influence of weather accelerated ageing (WAA). • Terminal blend rubber modification impart pronounced influence on healing temperature sensitivity of asphalt. • Weather accelerated aged asphalt has an obvious healing inertia zone with very low healing temperature sensitivity. • The greater the WAA resistance of asphalt, the smaller the WAA influence on healing temperature sensitivity. • WAA reduces the differences of healing temperature sensitivity among various asphalts. [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] • 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]

Asphalt rejuvenation technology is an effective method to recycle reclaimed asphalt pavement (RAP) for the production of high-quality recycled asphalt mixtures. This approach contributes to mitigating environmental pollution and facilitating resource recycling. In this study, the impact of rejuvenator molecules on the rejuvenation process was explored by utilizing theoretical models and dynamics simulations. Free volume theory models were used to calculate the diffusion coefficient, while molecular dynamics (MD) simulations revealed the internal energy changes during diffusion. Molecules with high interaction with aged asphalt are easier to reach the homogeneous state in diffusion systems under higher temperatures. The quantification of blending by Fick's 2nd law suggests that the blending process consists of three stages: an intense diffusion phase, a stabilization phase, and a homogeneous state phase. The time taken to reach the homogeneous stage depends on the chemical structure of the rejuvenators and the temperature. This study elucidates the molecular-scale mechanism of RAP rejuvenation and provides a roadmap for improving environmentally friendly RAP rejuvenation technology. • Blending process consists of three phases. • Interactions and free volume control the diffusion process. • Saturated-based molecules is more susceptible to high-temperature excitation. [ABSTRACT FROM AUTHOR]

Abstract Application of recycled concrete aggregate (RCA) in hot mix asphalt (HMA) is a sustainable alternative to natural aggregate. However, the increased asphalt consumption and decreased mechanical properties induced by the incorporation of RCA limit the extensive substitution of natural aggregates with RCA in HMA. In this paper, an experimental program was carried out to investigate the potential of recycled concrete aggregate pretreated with waste cooking oil residue (WCOR) with the expectation of reducing asphalt consumption and enhancing performance of HMA. The optimum pretreatment process for coarse and fine RCA in terms of content of WCOR, curing time and curing temperature was determined by an orthogonal design method and the grey correlation analysis. Subsequently, a laboratory characterization of HMA incorporating 40% coarse RCA, 40% coarse RCW (RCA pretreated with WCOR), 20% fine RCA and 20% fine RCW was further conducted in terms of optimum asphalt content, resistance to permanent deformation, cracking resistance at low temperature, fatigue performance, moisture sensitivity and dynamic modulus. Finally, scanning electron microscopy (SEM) test and fluorescence microscope (FM) test were performed to provide insight into the mechanism of WCOR-induced performance alteration. The experimental results showed that the pretreatment of RCA with WCOR decreased the optimum asphalt content from 5.4% to 4.5% for HMA incorporating 40% coarse RCA, from 5% to 4.5% for HMA incorporating 20% fine RCA. Moreover, RCA pretreated with WCOR enhanced significantly fatigue life and low temperature performance of HMA, while had a slight adverse effect on moisture sensitivity, permanent deformation resistance and dynamic modulus. Based on the SEM and FM tests, WCOR was observed to penetrate into tiny voids of cement mortar attached on RCA, which contributed to the reduction of optimum asphalt content and enhancement of fatigue life and low temperature performance of HMA. [ABSTRACT FROM AUTHOR]

Waste cooking oil residues (WCOR) based bio-asphalt is a potential substitute for petroleum asphalt. This study aims to prepare a bio-asphalt with high percentage of WCOR derived from esterification reaction for biodiesel. According to the uniform design results, the optimum mass ratios of materials were determined as WCOR of 33.3%, resin (RE-1) of 30.3%, hard asphalt particles (HAP) of 31.8%, low density polyethylene particles (LDPE) of 4.6% and linear SBS (L-SBS) of 4%. Based on the orthogonal design results, the WCOR based bio-asphalt would have the best performance when stirred for 40 min and sheared for 50 min (4000 rpm) under the condition of 170 °C with the optimum mass ratios. Rotational viscosity (RV) test results indicated that the viscosity of optimal bio-asphalt (OBA) was between PEN 70 base asphalt (PEN 70) and SBS modified asphalt (SBS-MA). Dynamic shear rheometer (DSR) test and bending beam rheometer (BBR) test results proved that OBA exhibited excellent high-temperature performance similar with SBS-MA, and it had superior low-temperature performance to SBS-MA and PEN 70. Furthermore, the effect of thermo-oxidative aging on the properties of OBA was studied. DSR test results revealed that the complex modulus and phase angle of thin film oven (TFO)-aged OBA both increased with the elevated aging level, indicating an increase in viscosity during aging process. Fourier transform infrared spectroscopy (FTIR) test results showed that there was no obvious variation on the functional groups of OBA after 15 h TFOT aging process. It was confirmed that less aging susceptibility of OBA was found compared with PEN 70, which demonstrated that OBA had a better aging resistance performance. [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]

In this study, the correlation between low-temperature performance of the crumb rubber modified asphalt (CRMA) binders and their chemical fractions was investigated. The low-temperature properties of CRMA binders were firstly characterized by creep stiffness and creep rate using the bending beam rheometer (BBR) test. Secondly, the SARA fractions, namely saturates, aromatics, resins, and asphaltenes, were separated from CRMA binders using an improved column chromatography method. Meanwhile, the functional groups and the derived indexes of CRMA binders and SARA fractions were characterized using Fourier transform infrared (FTIR) spectra, respectively. Finally, statistical modeling was conducted between low-temperature properties and functional groups of CRMA binders and their SARA fractions. The results showed SARA fractions from CRMA binders contained substances released from the partially degraded crumb rubber modifiers, indicated by the emergence of peaks at 1100 cm−1, 967 cm−1, and other wavenumbers in FTIR spectra. The substance exchanges played a positive role in improving the low-temperature performance of CRMA binders. Meanwhile, the addition of crumb rubber could effectively inhibit the increase of polar functional groups in the aging process, such as carbonyl of aromatics, resins, and asphaltenes fractions. This thus significantly resisted the aging and improved the low-temperature performance of CRMA binders. Finally, the statistical modeling showed the stiffness modulus and creep rate of CRMA binders were highly correlated with functional groups of aromatics, resins and asphaltenes. This indicated that SARA fractions significantly affected the low-temperature properties of CRMA binders. [Display omitted] •SARA fractions were separated from CRMA binders using an improved column chromatography method. •FTIR spectra of base and CRMA binders as well as SARA fractions were compared. •Statistical modeling was conducted between the low-temperature properties of CRMA binders and functional groups of their SARA fractions. [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]

• 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]