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The asphalt binder is exposed to unfavorable coupling aging of UV radiation, high temperature, and moisture, which accelerates the deterioration of the binder's rheological properties. To investigate the effect of this coupled aging on the rheological properties of asphalt binder, an accelerated environmental aging oven considering ultraviolet (UV) radiation, temperature, and moisture was used in this paper to carry out multifactor coupling aging tests for the binder. The coupling aging test parameters are determined by the central composite design-response surface methodology (CCD-RSM). The rheological properties of asphalt binder before and after aging were examined by dynamic shear rheometer, and the effects of the coupling aging on the viscoelastic, high-temperature, fatigue, and low-temperature properties of the binders were evaluated by employing the complex shear modulus (G*); the aging index (GI), which was established with G* ; the rutting factor (G*/sinδ); the Glover–Rowe (G-R) parameter; and the ratio of asphalt binder creep rate to stiffness modulus (m/S), respectively. Further, the effect of the coupling aging on the chemical properties of the asphalt binder was evaluated with carbonyl index obtained from the Fourier transform infrared spectrometer. The results showed that the optimal values (temperature: 68.3°C; irradiation intensity: 2,221 W/m2 ; spraying interval: 250 min) of the coupled aging parameters were determined by the CCD-RSM, and the relationship between the coupled aging time and the carbonyl index was established by the Verhulst model with an R2 value larger than 0.98. As the coupling aging degree increases, the G* , GI , and G*/sinδ show an increasing trend, whereas the G-R parameter, m/S , shows a decreasing trend, indicating that the aging increases the stiffness and high-temperature resistance of the binder and decreases its fatigue properties and low-temperature properties. Based on the correlation analysis, the G-R parameter showed good correlation with the GI , G*/sinδ (45°C, 55°C, and 65°C), m/S (−6°C , −12°C , and −18°C), respectively, and the average R2 value is larger than 0.98. Therefore, the G-R parameter can be used as a comprehensive index for evaluating the rheological properties of binders. [ABSTRACT FROM AUTHOR]

The adhesion between asphalt binder and aggregate is very important to the performance and durability of asphalt pavement. In order to explore the characterisation of modified asphalt binder in microstructure during aging and rejuvenation, the virgin asphalt binder and three kinds of modified asphalt binder (styrene‐butadiene‐styrene block copolymer (SBS), rubber powder and high viscosity and high elasticity [HVHE] modifier) in different aging and rejuvenation condition were prepared. The micromorphology and surface adhesion were measured by atomic force microscopy. The average roughness value was used as the index to evaluate the micromorphology of asphalt binder. The surface adhesion was used as the index to evaluate the adhesion properties of asphalt binder. Results show that the "bee" structure of SBS‐modified asphalt binder increased slightly after long‐term aging, and the recovery effect of aromatics oil was the closest to that of the unaged one. The rubber powder‐modified asphalt binder and HVHE‐modified asphalt binder showed the spot structure. And no matter for short‐term aging or long‐term aging, aromatics oil had the best recovery effect on micro morphology. The adhesion of the three modified asphalts would decrease gradually after aging. The effects of three kinds of rejuvenator on the adhesion of SBS‐modified asphalt binder and rubber powder‐modified asphalt binder were different. Rejuvenator, aromatic oil and warm mix asphalt mixture (WMA) additive could rejuvenate the loss of adhesion of HVHE‐modified asphalt binder to a certain extent. [ABSTRACT FROM AUTHOR]

The property of asphalt mastics consisting of asphalt binder and mineral fillers significantly affects the performance of asphalt mixture and also results in several forms of distresses in pavements. In addition to the materials properties, the interfacial interaction between asphalt binder and mineral fillers has a significant impact on the performance of asphalt mastics. This research aims to study the influence factors of interaction between asphalt binder and mineral fillers, and explore its relationship to viscoelasticity of asphalt mastics. Two kinds of asphalt binders, four kinds of mineral fillers and five filler/asphalt ratios were selected to prepare forty asphalt mastic samples. The interaction degree between asphalt binder and mineral fillers was characterised by a new introduced parameter C. The influence factors including the properties of asphalt and fillers were analysed. The correlations between interaction and mastics' rheological properties at different temperatures were statistically investigated. Results show that increasing the polar components ratio of asphalt binder, raising the specific surface area of fillers, making the size composition of fillers finer or increasing temperature all can increase the interaction degree between asphalt binder and mineral fillers. Linear relationship was considered to be an optimum type to represent the correlation between interaction degree and viscoelastic properties of asphalt mastic at temperatures between 15°C and 65°C. There was a very significant correlation between dynamic shear modulus/rutting factor/fatigue factor and C value when the temperature was between 25°C and 45°C. This kind of correlation weakened at 15°C and 55°C, but still significant. The phase angle of asphalt mastic has a significant correlation with interaction parameter C value only at 25°C and 35°C. [ABSTRACT FROM AUTHOR]

The interfacial behavior between asphalt binder and mineral fillers directly effects the performance of asphalt mastics or asphalt mixture. However, the understanding about the interfacial interaction between these components is very limited, although the role of individual ingredients on its performance is readily recognized. In order to study the interactions between asphalt binder and mineral fillers, it is necessary to propose an effective evaluation indicator. In this research, dynamic mechanical analysis (DMA) was used to obtain the viscoelastic parameters of different asphalt binder and asphalt mastics. The interfacial interaction parameters between asphalt binder and fillers were calculated based on the viscoelastic parameters and relevant theoretical models. The interaction parameters were compared and the calculated methods were improved. The results show that compared to interfacial interaction parameters Luis Ibrarra- A and K. Ziegel- B , C value based on Palierne theoretical model had the least sensitivity to the volume fraction of fillers. The checking of fitting goodness of improved interaction parameter C value shows a high determination coefficient. It demonstrates that the C value can effectively evaluate the interfacial interaction. The interfacial interaction becomes stronger with the temperature increasing. The higher the specific surface area of filler, he stronger the interfacial interaction between it and asphalt binder. [ABSTRACT FROM AUTHOR]

• The periodic perturbation method is adopted to calculate the ZSV of asphalt binder MD models. • Asphaltene and saturates more easily reorient their conformation in shear flow. • Short, unordered planar accumulations structures dominate asphalt binder microstructure. This study aims to develop molecular model of asphalt binder and investigate the reasonable simulation scale of molecular dynamics (MD) in researching the viscosity property and microstructure of asphalt binder. Eighteen MD models with atom numbers in the range of 10,000–750,000 for the three typical asphalt binder AAA-1, AAK-1, and AAM-1 in the Strategic Highway Research Program (SHRP) were constructed. Density, Zero Shear Viscosity (ZSV), and microstructure characters of the asphalt binders were analyzed by MD to compare with experiment data. The result shows that densities and the ZSV values of the MD models are all close to the experimental values. These models with atom numbers of 130,000–375,000 are well stabilized and have lower errors, which is recommended to research the density and viscosity properties. In the shearing process, the shear flow induces the conformational transitions of the asphalt binder, and most molecules tend to parallel the shear direction. Asphaltenes and saturates components are easier to reorient their conformation in shear flow. Through the density map obtained by MD simulation and the asphaltenes image from the High-resolution transmission electron microscopy in literature, we speculate that short and unordered planar accumulations structures dominate the asphalt binder microstructure, which is a further explanation of the colloidal theory. [ABSTRACT FROM AUTHOR]

• Investigated the effects of damage and thixotropy on viscoelastic parameters; • Obtained a linear relationship between G ∗ E and θ under the influence of thixotropy; • Developed a thixotropy model to characterize the change of G ∗ E under the influence of thixotropy; • Calculated damaged density separating the influence of thixotropy. Accurate characterization of the fatigue resistance of asphalt binder is of great significance to the prediction of asphalt pavement performance. Traditionally, apparent changes in viscoelastic parameters, including dynamic shear modulus and phase angle, with the number of loading cycles are used to define the fatigue performance of the asphalt binder. However, thixotropy also leads to changes in these viscoelastic parameters, and its contribution is not yet well understood. This study develops a method to quantify the effects of damage and thixotropy on the changes of viscoelastic parameters under the cyclic stress-controlled loading mode. The new method includes the four key steps: (1) determining the thixotropy influence-dominated phase; (2) establishing a thixotropy model to characterize the influence of thixotropy on the effective dynamic shear modulus; (3) calculating damage density from the apparent and effective dynamic shear moduli; and (4) characterizing thixotropy behavior based on Black space diagram. The effectiveness of the newly developed method is verified by the time sweep test, which is conducted on two types of asphalt binder under varying stress levels.with a loading frequency of 10 Hz and a test temperature of 25 °C. The results show that: (1) the change of dynamic shear modulus is resulted from the damage and thixotropy, while that of phase angle is only caused by the thixotropy; (2) thixotropy leads to the decrease of dynamic shear modulus and increase of phase angle; and its influence on viscoelastic parameters increases with the loading time and stress level increased; (3) under the influence of thixotropy, the dynamic shear modulus is linearly related to the phase angle, which is independent of the stress level applied and the damage accumulated in the asphalt binder. [ABSTRACT FROM AUTHOR]

Highlights: [•] Long rest periods and few loading cycles result in improved healing. [•] The effect of terminal cases on healing is greater than the effect of rest periods. [•] We established a universal healing evaluation index for asphalt binder. [•] The healing ranking of binders suggested by HIm-c, HIem-c and HIvm-c are the same. [•] The healing ranking of the binders is the same as the ranking of the corresponding. [ABSTRACT FROM AUTHOR]

Abstract: Asphalt binder has a critical effect on the performance of asphalt mixtures. Thus, asphalt binder is of great concern to pavement engineers and researchers. Usually, asphalt binder is studied in dynamic space and steady-state space separately, and the property indices are researched separately. As researchers delved deeper, they found that it is important to combine the dynamic properties and steady-state properties, especially for establishing rheological curves and constitutive equations. The Cox–Merz relationship can connect the properties in dynamic space to those in steady-state space. This relationship is widely used in polymer system and shows good results. This study focused on the applicability of the Cox–Merz relationship as it pertains to asphalt binder. The Cox–Merz relationship was applied to six neat asphalt binders. Then, the applicability of the Cox–Merz relationship for asphalt binder was studied and the criterion to verify whether the Cox–Merz relationship is followed or not was established. Finally the viscosity functions when the Cox–Merz relationship used were studied, and the Cross model and the Carreau model were compared. The results show that the Cox–Merz relationship is followed in the shear-thinning region and not always followed in the zero-shear-rate-limiting viscosity region, and it is useful when obtaining the viscosity function. [Copyright &y& Elsevier]

Abstract: The healing performance of asphalt binder has a critical impact on the fatigue performance of asphalt binders, mixture and pavement. Although studies of the healing characteristics of asphalt binder can be found in some references, the subject has not been researched thoroughly. No universal healing evaluation index currently exists, and the fatigue and healing processes are not fully understood. For this study, experiments were performed to characterize the healing characteristics of four typical asphalt binders. Healing indices are put forward, and factors that affect healing performance are examined in this paper. Finally, the fatigue and healing processes of asphalt binder are investigated by analyzing test specimen cross-sections. The findings from this study, although based on a limited number of binders, suggests that HI1 (the modulus ratio) and HI2 (the cycle number ratio) are suitable healing indices. Rest periods and microstructural configurations significantly affect the healing performance of asphalt binder. Healing affects the fatigue performance only when the modulus value is greater than the modulus value when rest periods are applied. During fatigue testing, damage starts at the outer edge of the specimen, and then develops towards the middle of the specimen. [Copyright &y& Elsevier]

[Display omitted] • Cracking performance of asphalt binder was studied using various rheological indicators. • G-R parameters and ΔT c are most sensitive to aging effects. • G-R parameter is the potential indicator for evaluating the low-temperature cracking of asphalt binders. • The aging model using G-R parameter could describe the aging rule of asphalt binder. The cracking resistance of asphalt pavement is significantly affected by the aging of asphalt binder. A better understanding of the effect of aging on the cracking resistance of virgin asphalt binders can help to determine the optimum maintenance time. In this study, the rolling thin film oven test (RTFOT) and pressure aging vessel (PAV) test were conducted to simulate short-term aging and long-term aging of asphalt binders, respectively. Frequency sweep tests were conducted on two asphalt binders at different aging conditions. The Glover-Rowe (G-R) parameter, stiffness modulus (S), creep rate (m), continuous grading temperature (T c), critical temperature difference (ΔT c), relaxation time (λ), dissipation energy ratio (W d /W s), low-temperature indicator ratio (m/S), low-temperature comprehensive compliance parameter (J c) were obtained. Meanwhile, the sensitivities of different indicators to aging were analyzed and the correlations between G-R parameter and various low-temperature indicators were discussed. Subsequently, a nonlinear model of asphalt binder aging was established by a rheological indicator. The results showed that aging had a significant impact on the low-temperature properties of asphalt binder. G-R parameter, T c , λ increased with the growth of aging severity, whereas m , ΔT c , W d /W s were contrary to this trend. S , m/S , J c had no significant relationship with the degree of aging. Moreover, G-R parameter and ΔT c were very sensitive to aging. The G-R parameter had a good correlation with m , T c , λ, ΔT c and W d /W s , respectively. It indicated that G-R parameter was closely related to the low-temperature properties of asphalt binders. The aging nonlinear model containing G-R parameter could exactly describe the aging evolution of virgin asphalt binder. It is helpful for the prediction of cracking resistance of asphalt binder and determination of maintenance plan. [ABSTRACT FROM AUTHOR]

The high- and low-temperature performance of asphalt binders have an important effect on the rutting and cracking resistance of asphalt pavements, thus these are two of the most important performance of asphalt binders. Nowadays, there are many indices to evaluate the high- or low-temperature performance of asphalt binders respectively. But there is still no unified option about which index is better. As a kind of typical viscoelastic materials, both of the high-temperature performance and the low-temperature performance of asphalt binders are related to viscoelastic characteristics of asphalt binders, but they are opposite to each other. That is, a binder needs to have more elastic part for high-temperature performance but more viscous part for low-temperature performance. So the ratio of viscous part to elastic part is important to high- and low-temperature performance of asphalt binders. Based on that thought, a new index based on viscoelastic characteristics, referred to as R J , is developed in this study. Different high- and low-temperature evaluation indices including R J were analyzed by comparing the performance ranking evaluated by them with the ranking of the corresponding mixtures. The correlation between performance of binders evaluated by different indices and the performance of the corresponding mixtures were also analyzed. Based on the results, zero shear-rate viscosity and non-recoverable stiffness is found to be suitable for evaluating the high-temperature performance of asphalt binders, stiffness at 60 s from BBR is found to be suitable for evaluating the low-temperature performance of asphalt binders. The established evaluation index, R J , is found to be suitable for evaluating both performances of asphalt binders. [ABSTRACT FROM AUTHOR]

• A complex index was developed to fully capture the recovery evolution of asphalt binder. • Modulus recovery and fatigue recovery of asphalt binder were quantified through the real and imaninary components of the complex index, respectively. • The fatigue resistance recovery always lags behind the modulus recovery. • The property recovery evolution of a damaged asphalt binder can be divided into three stages with different dominant mechanisms. Accurate quantification of recovery potential of asphalt binder is crucial to the asphalt pavement performance assessment and pavement design. A new unified complex recovery index was developed to effectively capture the asphalt recovery evolution after cyclic loading, including the modulus recovery and the fatigue resistance recovery. The recovery master curve was developed based on the rest-damage superposition principle (RDSP), which can quantify the recovery of modulus and fatigue resistance over a wide rest time range. Results indicate that the recovery process can be divided into three stages, in which the fatigue resistance recovery always lags behind the modulus recovery. [ABSTRACT FROM AUTHOR]

• G ∗ and δ satisfy a linear relationship under the influence of thixotropy. • Thixotropy is the only physical phenomenon leading to the recovery of δ. • The recovery of G ∗ is resulted from self-healing and thixotropy. • Healing ability is overestimated without separating the influence of thixotropy. Considering the self-healing property of asphalt binders in material selection and pavement design can help improve pavement performance and reduce maintenance costs. The study of self-healing of asphalt materials gradually is becoming an important step in the design of durable pavements. Traditionally, the performance recovery of asphalt binders has been attributed only to microcrack healing, which may lead to an overestimation of the self-healing ability. This is because an increasing number of studies have shown that the driving mechanism of asphalt binder performance recovery includes not only self-healing but also thixotropy. In order to accurately quantify the self-healing ability of asphalt binders without the influence of thixotropy, a novel test procedure and a three-step analysis method are proposed. The novel test procedure includes the large amplitude time sweep test and the small amplitude time sweep test. The three-step analysis method consists of establishing a thixotropy relationship between the dynamic shear modulus and the phase angle, calculating the effective modulus from the phase angle data via the thixotropy relationship, and determing the healing degree of asphalt binders by separating the thixotropy. The results show that the recovery of the dynamic shear modulus of asphalt materials results from the combined action of thixotropy and self-healing. And thixotropy plays a prominent role in the dynamic shear modulus recovery at the initial resting period. The contribution of self-healing to dynamic shear modulus recovery gradually increases with increasing resting time. Without excluding the influence of thixotropy, the self-healing ability of asphalt binders is overestimated, especially the short-term self-healing ability. [ABSTRACT FROM AUTHOR]

[Display omitted] • The adhesions between asphalt binder and material aggregate in different environments were quantitatively analyzed. • Ultrasonic wave can simulate the dynamic water pressure removing the asphalt binder from the mineral aggregate surface. • A high degree of correlation exists between the work of adhesion index and the pull-off strength index. The adhesion between asphalt binder and mineral aggregate directly determines the performance of asphalt pavement, which could be effected significantly affected by light, oxygen, water and other natural conditions. In order to investigate the effect of different environmental conditions on the adhesion between asphalt binder and mineral aggregate, virgin asphalt binder with 70 (0.1 mm) penetration and SBS modified asphalt before and after aging were used as test samples in this study. The effect of aging, testing temperature and relative humidity on adhesion between asphalt binder and mineral aggregate was quantitatively analyzed by using the surface energy theory. The results show that aging reduced the content of resin, increase the content of asphaltene, which resulted in the deterioration of adhesion performance of asphalt binder. The anti-aging performance of SBS modified asphalt was better than virgin asphalt binder in terms of adhesion. The work of adhesion between asphalt binder and mineral aggregate increased when the testing temperature of asphalt binder increased from 0 °C to 80 °C. The work of adhesion between virgin asphalt binder and material aggregate increased much higher than SBS modified asphalt. Asphalt binder was not sensitive to the change of relative humidity, but the total amount of surface energy parameters of the mineral aggregate decreases linearly with the relative humidity increasing. The work of adhesion between asphalt binder and granite aggregate was more likely to be affected by external gaseous water molecules. In order to simulate the real hydrodynamic pressure, the pull-off test was improved by adding ultrasonic wave. The ultrasonic tests' results show that the water invaded the interface between asphalt binder and material aggregate, accelerated the adhesion failure. A strong linear correlation exists between the work of adhesion and the ultrasonic pull-off strength. [ABSTRACT FROM AUTHOR]

[Display omitted] • The reversibility index R M of aging and rejuvenation of modified asphalt is proposed. • R M can be used to evaluate the effect of different rejuvenators. • R M can characterize the recovery of rheological properties of asphalt. • The aging and rejuvenation process of virgin and modified asphalt is different. In order to study the reversibility between aging and rejuvenation of modified asphalt binder, a kind of virgin asphalt was selected, and then three kinds of modified asphalt were prepared based on this virgin asphalt. The short-term and long-term aging tests were carried out for the four asphalts. Then three kinds of rejuvenation tests were carried out for the aged asphalt, including commercial rejuvenator, aromatic oil and warm mix rejuvenator. Dynamic shear rheometer (DSR) was used to carry out frequency scanning tests at different temperatures. According to the principle of time temperature equivalence, the master curves of different modified asphalts were constructed, and the rheological properties of asphalt during aging and rejuvenation were studied. By comparing the parameters including complex modulus and hardening index, the rejuvenation effects of viscoelastic properties of modified asphalt were evaluated. Based on the complex modulus of virgin asphalt and modified asphalt, the aging rejuvenation reversible index R M of modified asphalt is proposed to evaluate the recovery of rheological properties of asphalt by different rejuvenators. The results show that the modulus of three kinds of modified asphalt will increase with the deepening of aging. Warm mix rejuvenator can reduce the complex modulus of virgin asphalt, SBS modified asphalt and rubber powder modified asphalt most significantly, followed by the rejuvenator, and the aromatics oil reduced least obviously. This applied to both short-term aging and long-term aging. This research provides a better understanding on the effectiveness and limitation of current rejuvenation techniques and rejuvenators on common asphalts, which is good for the further improvement on production and techniques. [ABSTRACT FROM AUTHOR]