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Mesoscale contact networks for asphalt mixtures play a crucial role in load resistance. However, there is a lack of quantitative characterization methods for contact networks. Topology can describe the contact relationships between multiple objects through points and lines. In this study, aggregate information was extracted by industrial computed tomography (CT) and digital image processing technology (DIP). The classification of disruption aggregates was determined by a two-dimensional (2D) topological contact model. Then, the correlation mechanism between topological indices and topologies was established based on the topological matrix. The algebraic connectivity (La) of nine different asphalt mixture disruption aggregates was analyzed. The results revealed that each type of asphalt mixture disruption aggregate was dominated by a certain La with higher frequency. As the nominal maximum size (NMAS) increased, there was a shift in the dominant topologies of different asphalt mixture disruption aggregates from those associated with lower La to those linked to higher La. Based on the higher frequency of La, there were 8 topologies with frequencies exceeding 20%; 5 with frequencies surpassing 10%; and 14 and 17 with frequencies greater than 5% and 2%, respectively. Furthermore, it was observed that the topologies of disruption aggregates predominantly consisted of simple topologies. Additionally, the frequency of complex topologies decreased as the number of nodes and connectivity increased. [ABSTRACT FROM AUTHOR]

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]

This study investigated the effects of a diatomite/tetradecane composite shaped phase change material (CSPCM) on the mechanical properties and thermoregulation performance of styrene-butadiene-styrene (SBS)- and styrene-butadiene-styrene/crumb rubber (SBS/CR)-modified asphalt binders. The heat transfer and latent heat characteristics of phase change asphalt mortars (PCAMs) were analyzed using a thermal constant analyzer and differential scanning calorimeter. Furthermore, a thermoregulation test was devised to confirm the temperature-regulating characteristics of PCAMs. The rheological properties of PCAMs were analyzed using the dynamic mechanical analysis (DMA) method, and low-temperature fracture characteristics were evaluated using the single edge notched beam (SENB) test. The results indicated that the incorporation of CSPCM decreased the thermal conductivity and thermal diffusivity of SBS- and SBS/CR-modified asphalt binders but increased their specific heat capacity. CSPCM can be stably present in modified asphalt and still have good phase change properties in the phase change temperature range, as well as the temperature regulation effect of PCAMs is excellent. The melting enthalpy for the PCAMs was as high as 73.29 J/g. Compared to the modified asphalts, the heating time of the PCAMs increased by up to 34.1% as the dosage of CSPCM gradually increased. The incorporation of CSPCM enhanced the viscous components of modified asphalt binders, improved intermediate-temperature fatigue resistance and low-temperature fracture resistance, and reduced high-temperature permanent deformation resistance. [ABSTRACT FROM AUTHOR]

In order to effectively evaluate the regeneration effects of different rejuvenators on aged asphalt binder, this study carried out a series of tests and evaluations on the macroperformance of virgin asphalt binder at various aging-regeneration stages. A commercial rejuvenator, aromatic oil, and warm mix agent were selected as rejuvenators. Fifteen asphalt binder samples involved various aging methods, including water-ultraviolet aging, water-free ultraviolet aging, rolling thin film oven test (RTFOT), and accelerated aging by pressurized aging vessel (PAV). High-temperature properties of asphalt binders were evaluated by softening point, and low-temperature properties of asphalt binders were evaluated by stiffness modulus and m-value. The viscoelastic properties were evaluated by complex modulus G*. Test results show that the regeneration effects of different rejuvenators were reflected in the reduction of softening point, stiffness modulus, and complex modulus. Based on performance changes of asphalt binder before and after aging, the reversibility indexes Rsp , RG* , RS , and Rm for quantitative evaluation of macroperformance of rejuvenated asphalt binders were proposed. Through linear fitting, it was found that R2 between the reversibility index Rsp and the reversibility index RG* reached 0.7574, and R2 between RS and Rm reached 0.8683. This provided the possibility of mutual transformation between those reversibility indexes. Last, the macroreversibility index of virgin asphalt binder (ARIV) was proposed. The softening point and stiffness modulus were taken as representative indexes to comprehensively evaluate the recovery of high-temperature, low-temperature, and viscoelastic properties of aged asphalt binder by different rejuvenators. This study provided a unified indicator to quantitatively evaluate the regeneration effect of rejuvenator on virgin asphalt binder. It is helpful for better understanding the aging-regeneration process of virgin asphalt binder and determining the optimum regeneration time and rejuvenator. [ABSTRACT FROM AUTHOR]