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Individual effect of aging and rejuvenator recycling on basic properties of asphalt is readily recognized, but there is only limited understanding about whether the recycling of SBS- (styrene-butadiene-styrene-) modified asphalt is an inverse process of aging or not. To compare the effects of aging and rejuvenator on microproperties and molecular composition of SBS-modified asphalt, comprehensive performance tests and physical-chemistry experiments were conducted. The results of infrared spectroscopy tests demonstrate that the reticular crosslinking structure of asphalt was destroyed and SBS's modification effect was gradually lost after aging. This can cause the strengthening of high-temperature performance and reduction of the low-temperature anticrack property of SBS-modified asphalt. Scanning electron microscope shows that the island structure of SBS-modified asphalt disappeared after aging. Energy spectrum analysis shows that the C (carbon) content of aged SBS-modified asphalt has decreased, while the O (oxygen) content and S (sulfur) content have increased obviously. Results of the fluorescence microscope, SEM, and rheological tests show that the epoxy functional group compounds of aliphatic glycidyl ether resin had high reactivity; the triblock molecular structure of SBS and the mechanical performance of SBS-modified asphalt were recovered. [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]

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]

An asphalt mastic imparts most of its characteristics to the asphalt concrete mixture and also dictates several forms of distresses in asphalt mixtures and pavements. Several studies have demonstrated that the interaction between asphalt binder and mineral fillers has a significant impact on the properties and performance of asphalt mastics and mixtures. The objective of this study was to investigate the nature of binder adsorption on mineral filler surface while simultaneously quantifying the influence of such adsorption on the properties of the binder in the immediate vicinity of the interface and bulk. An adsorption test using mineral fillers and binders was conducted to achieve this goal along with measurements of asphaltene content and rheology on the original binder and the residual binder from the adsorption tests. Results show that polar fractions preferentially adhered to the surface of the mineral filler. Such preferential adsorption resulted in a significant increase in the complex modulus of the adsorbed or fixed asphalt with a concomitant decrease in the complex modulus of the free or bulk asphalt binder. These changes in complex modulus varied only slightly as a function of the frequency. The magnitude of adsorption was dictated by the mineral nature of the surface and more importantly by the specific surface area of the particles. The findings from this study are useful to better understand and model the failure mechanisms in the micro structure of asphalt composites. [ABSTRACT FROM AUTHOR]

Although the role of individual ingredients of hot mix asphalt (HMA) such as asphalt binder and aggregates on its performance is readily recognized, there is only limited understanding about the interactions between these components and the properties of binder-aggregate interface. In order to study the interactions between asphalt binder and mineral aggregates, an interfacial test method was developed and its effectiveness was evaluated. Interfacial interactions were evaluated by testing thin films of an asphalt binder interfaced with the surface of aggregates under two different modes of loading in shear: sinusoidal oscillation and monotonically increasing. An Interaction Parameter ( IP ) was proposed to quantify the binder-aggregate interfacial effects. The results show that the methodology used in this study can quantify the effects of interaction between the asphalt binder and mineral aggregates. Furthermore, this research also investigated the interaction of an asphalt binder with the surface of simulated reclaimed asphalt pavement (RAP) aggregates. The results from this research not only provide an insight to the effects of binder-aggregate interaction, but can also help practitioners to better understand the effect of mixing conditions on the properties of mixtures produced using different materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • The accelerated thermal cycling test was conducted on two asphalt mastics. • Microstructural characteristics evolution was measured using AFM. • Correlation between macro and micro properties was established. • SBS modified asphalt mastic demonstrates great resistance to cyclic temperature variations. • Bee structure ratio, adhesion, and I RAD can characterize the thermal cycling deterioration. Environmental temperature-effect is the primary factor responsible for asphalt pavement failure. Asphalt pavement exposed to the atmosphere is constantly subjected to the thermal cycles induced by environmental temperature fluctuations, and the resulting thermal cracks significantly reduce the durability of asphalt pavement. Nevertheless, the influence of cyclic temperature variations on the performance degradation of asphalt binder materials is often overlooked. To address this, accelerated thermal cycling test was conducted on two asphalt mastics to simulate repeated environmental temperature variations. Dynamic shear rheological test (DSR) and atomic force microscopy test (AFM) were performed to characterize the evolution of the macroscopic rheological properties and microstructural characteristics under five cyclic temperature ranges. Pearson correlation analysis was utilized to explore the correlation between macro and micro properties. Following thermal cycling, it was observed that the two asphalt mastics experienced a decline in their viscous properties and became more elastic, resulting in a decrease in their stress relaxation capacity and asphalt-aggregate interaction on a macroscopic level. The microstructure transitioned from a multiphase to a homogeneous structure, while the expansion of the valley structure indicated the accumulation of microscopic defects. The larger the temperature variations and the higher the cyclic temperatures are, the more severe the deterioration in the viscoelasticity and microstructures of asphalt mastics is; the degradation of the micromechanical characteristics directly affects the macroscopic rheological properties. The bee structure ratio, the adhesion, and relaxation properties are sensitive to cyclic temperature variations and recommended to characterize the thermal cycling resistance. In comparison to 90# asphalt mastic, the SBS modified asphalt mastic exhibits great resistance to thermal deterioration. This study deepens the understanding of the causes of asphalt pavement performance deterioration in regions with frequent environmental temperature fluctuations. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Foamed asphalt mastic with different filler-asphalt binder ratios was produced. • The addition of filler into foamed asphalt exhibited a significant effect on rheological property. • The time-temperature superposition principle can be employed in foamed asphalt mastic. • The distribution of filler in base asphalt mastic was inferior to that in non-foamed asphalt mastic. Abstract Foamed warm asphalt has become an effective option to common asphalt technologies. It is quite significant for foamed asphalt to be used widely with regard to the mechanical investigation of foamed asphalt mastic. The objective of this study is to explore the rheological properties of non-foamed (base) and foamed asphalt mastics with different filler-binder ratios completely, by using the dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests, respectively. Also, the influence of filler-asphalt ratio on the high and low temperature performance of the base and foamed asphalt mastic was analyzed, and the effectiveness of time-temperature superposition principle was discussed for the foamed asphalt mastic. The master curves of base and foamed asphalt mastic were established and then the master curve was used for that to perform a rheological properties analysis over a wide range of temperatures and frequencies. In addition, this study investigated the micromechanics of the base and foamed asphalt mastic by using direct microstructure observations and thermal property testing, including scanning electron microscope (SEM) and differential scanning calorimeter (DSC). It was found that the addition of mineral filler into the foamed asphalt exhibited a significant influence on the high and low temperature performance. The time-temperature superposition principle can be employed in the foamed asphalt mastic. The foamed asphalt mastic showed better high temperature performance than the base asphalt mastic over a wide range of frequency. The low temperature PG grade of the foamed asphalt mastic indicated a favorable consistency with that of the base asphalt mastic. The distribution of filler in the base asphalt mastic was inferior to that in the basic asphalt mastic. The thermal stability of foamed asphalt mastic performed an obvious increase as compare to that of base asphalt mastic. [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]

Moisture vapor diffusion resulting from the difference in relative humidity between air and pavement material contributes to moisture damage. Understanding moisture vapor diffusion in asphalt pavement is the first task in the analysis of moisture damage. Analysis was conducted in an automated environmental chamber with a temperature precision of ± 0.5 °C and relative humidity precision of ± 3%. Moisture uptake profiles for fine aggregate mixtures (FAMs) under various environmental conditions (relative humidity and ambient air temperature) and constituent materials (aggregate and asphalt binder) were measured. Preliminary data analysis showed the existence of Non-Fickian diffusion behavior. Therefore, two non-Fickian and one Fickian models were introduced to fit the measured moisture uptake data and determine FAM diffusion characteristics, such as diffusion coefficient, diffused moisture phase, and time-variable diffusion. Based on the variation in FAM diffusion characteristics under various experimental conditions and constituent material combinations, sensitivity analysis was conducted with one-way ANOVA and the determinants of FAM vapor diffusion characteristics were proposed. [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]