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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]

To understand the effect of particulate contaminants on pavement skid resistance, the friction numbers of three surfaces under different pollution conditions (particle size, coverage fraction, and shape factor) were measured using a British Pendulum Tester (BPT). The results show that less than 45% coverage fraction of the particles above 0.3 mm even results in almost 50% friction loss at a low speed of 10 km/h. In this situation, the rougher surface has a stronger holding particles capacity. Moreover, the particle size determining the lowest friction level gradually increases as the surface roughness increases. The particle size of 1.18–2.36 mm is the most typical size range leading to a low friction level. In addition, the friction first drops sharply and then increases slowly with the coverage fraction increases, which also conforms to the Stribeck curve. The skid resistance of road surfaces covered with particles was tested. Effects of particle size, coverage fraction, and shape on friction were analysed. Potential hazard scenarios with particulate contaminants were discussed. [ABSTRACT FROM AUTHOR]

Crumb rubber can not only solve the environmental pressure but also improve the properties of bituminous pavement. To study the characteristics and mechanism of ozone aging on CRMB, the effects of ozone aging on the rheological properties and chemical composition of crumb rubber-modified bitumen (CRMB) were explored. It was also compared with thermal oxygen. The results show that the macromolecules such as aromatic rings and polar functional group were formed after ozone aging, and the average molecular weight of CRMB increased. Ozone reacted rapidly with the CRMB surface at the beginning of the reaction and leaded to an increase in surface roughness. The risk of fatigue cracking increased. The effect of ozone aging (3 days, 60°C, 1000 ppb) on CRMB was similar to that of long-term aging. The effect of ozone on CRMB was mainly due to the ozone sensitivity of the crumb rubber modifier. [ABSTRACT FROM AUTHOR]

This study focuses on mechanical strength and gradation optimisation of inorganic binder-stabilised material with iron tailings for pavement engineering. The mechanical strength and compatibility of iron tailings mortar with various inorganic binders were explored. Mechanical strength formation of iron tailings mortar was analysed using hydration products, micromorphology and microstructures. Composition optimisation of inorganic binder-stabilised material with iron tailings was discussed using the central composite design-response surface method. Results showed that the mechanical strength formation of iron tailings mortar is primarily dependent on ettringite and calcium silicate hydrate (C–S–H) gels. Iron tailings mortars with an appropriate amount of lime or fly ash replacement of cement exhibit a denser structure and adequate pore structure distribution that help improve their mechanical properties compared with cement iron tailings mortars. To balance the amount of iron tailings and the strength of cement-stabilised material, optimal application conditions were proposed for different levels of highways. [ABSTRACT FROM AUTHOR]