This paper aims to optimize the asphalt-mortar interface characteristics of semi-flexible pavement coating material (SFPCM), three types of the interface modifiers, namely the silane coupling agent, carboxylated styrene-butadiene latex, and cationic emulsified asphalt, are selected to add into the cement mortar to optimize the asphalt-mortar interface. The microscopic characteristics of the asphalt-mortar interface and the macroscopic pavement performance of the SFPCM after the interface optimization are investigated to reveal the effect of interface modifiers and determine the best formula. Results show that: (1) The dry shrinkage of the cement mortar is increased with the increased dosage of the interface modifiers, while the strength is decreased accordingly; (2) the optimum dosages of the silane coupling agent, carboxylated styrene butadiene latex, and cationic emulsified asphalt are 0.5%, 10%, and 5%, respectively; (3) the microscopic asphalt-mortar interface characteristics of the SFPCM with different interface modifiers have significant differences; (4) the SFPCM with the cationic emulsified asphalt presents the best pavement performance, particularly the high-temperature stability. These results can be attributed to improve the pavement properties of SFPCM.

The low-temperature crack of asphalt concrete is considered to be one of the main deteriorations in asphalt pavements. However, there have been few studies on the composite effects of the aggregate characteristics and fracturing modes on the low-temperature cracking of asphalt concrete. Hence, the edge cracked semi-circular bend tests and the discrete element modeling approaches are combined to investigate the effect of the aggregate contents, aggregate morphological features and aggregate distributions on the fracture behavior of asphalt concrete in different fracturing modes at different temperatures. The results show that the fracture toughness and the crack extended time reduce with the increasing aggregate orientation and flatness and the decreased aggregate content. The effect of aggregate flatness is nonlinear, and its reduction trend grows gradually with the increasing flatness. The total number of failed contacts is reduced with the increasing aggregate orientation and flatness, particularly at 10 °C. The number of failed contacts that occurred in the aggregate–mastic interface in Quasi-Mode II fracturing is slightly higher than that in other fracturing modes. The aggregate distribution in the crack initiation zone greatly influenced the crack resistance, particularly at 10 °C. The research is beneficial to better understand the fracture mechanisms of asphalt concrete at low-temperature.

Ceramsite concrete is one of the most widely used lightweight concretes at present. Although mechanical properties of ceramsite concrete have been extensively discussed, its permeability characteristics are neglected in previous studies. Considering the importance of permeability resistance to concrete, the permeability grade and residual compressive strength after permeability of ceramsite concrete are analyzed in this study. The influence of ceramsite content and size on the permeability grade and residual strength of ceramsite concrete were investigated by the orthogonal experimental method. To further understand the above influence, an improved Bayesian framework for small sample data is also established to analyze the permeability grade and residual strength. Results show that the water–binder ratio and the content of 20–30 mm ceramsite aggregates are the most and least significant influencing factors affecting the permeability characteristics, respectively. The 5–10 mm and 10–20 mm ceramsite aggregates play secondary roles. Increasing 5–10 mm and 10–20 mm ceramsite aggregates is not helpful for improving the permeability resistance of ceramsite concrete. Compared with the orthogonal method, the proposed Bayesian framework is a useful tool for revealing the effects of various factors, which can cut the time cost and provide parameter visualization for the analysis process. Results show that the permeability resistance and residual strength of ceramsite concrete are improved significantly under optimal conditions. The permeability grade and residual strength are increased 200% and 80.3%, respectively. In addition, the residual strength may be more suitable for evaluating the permeability characteristics than the permeability grade.

The variation law and mechanism of the permeability characteristics of coal gangue ceramsite lightweight aggregate concrete (CLAC) remain unclear. Therefore, in this study, the effect of the ceramsite size and replacement ratio on the pore structure characteristics of the CLAC was analyzed by mercury pressure test. Moreover, based on a fractal approach, the relationship between permeability characteristics and pore structure of the CLAC was established. The results indicate that incorporating coal gangue ceramsite effectively decreases the maximum pore size. The fractal dimension increases as the replacement ratio of 20–30 mm and 10–20 mm ceramsite rises, whereas an opposite trend is observed when the content of 5–10 mm ceramsite increases. At moderate replacement levels, the introduction of ceramsite aggregates can reduce the fraction of detrimental pores and promote the formation of harmless and slightly harmful pores; however, at high replacement levels, the fraction of harmful and macropores may increase. Moreover, the fractal dimension is negatively correlated with the permeability grade and residual strength, but positively correlated with the strength degradation rate.

Estimating moisture susceptibility of asphalt modified with alumina trihydrate The moisture susceptibility of asphalt containing alumina trihydrate (ATH) was assessed through the surface free energy. Physical properties and flame retardancy of ATH samples were also investigated. For research purposes SBS modified asphalt samples with different dosages (0-14 %) of ATH were prepared. Increased viscosity, softening point limiting oxygen index and lower penetration ductility, were investigated for the ATH modified samples. ATH has a significant negative effect on the moisture-induced damage potential of asphalt mixture from the view of micromechanisms.