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In this study, the semicircle three-point bending tests of ordinary asphalt concrete and basalt fiber asphalt concrete were carried out and acoustic emission parameters were collected during the test. The differences of the characteristics of acoustic emission parameters between basalt fiber asphalt concrete and ordinary asphalt concrete were analyzed, and the damage stages were divided based on the variation of acoustic emission parameters; Rise Angle and Average Frequency were introduced to study the cracking mode and crack resistance mechanism of asphalt concrete with basalt fiber. The results show that the acoustic emission parameters can well represent the toughening and crack resistance effect of basalt fiber in asphalt concrete, and the damage stages can be divided into three stages: microcrack initiation stage, fracture stage, and residual stage. The duration of the fracture stage and the load resistance time of the specimen were greatly prolonged. The proportion of shear events in the whole failure process increased greatly after the basalt fibers were added, especially in the fracture stage, which reduced the tensile failure tendency of the specimens, and thus improved the bending and tensile performance of the specimens and played a toughening and crack resistance role in the fracture stage. [ABSTRACT FROM AUTHOR]

• The effect of fiber on the mechanical properties of emulsified asphalt cold recycled mixture is analyzed. • Basalt fiber improves crack resistance of emulsified asphalt cold recycled mixture. • Fracture behavior of fiber reinforced emulsified asphalt cold recycled mixture is studied using acoustic emission (AE). • The acoustic emission parameters are consistent with the change of the load–displacement curve. • Micromorphology and microstructure of basalt fiber emulsified asphalt cold recycled mixture were observed. In the present study, to solve the problem of poor early strength and crack resistance of emulsified asphalt cold recycled mixture, the enhancement and fracture mechanism of fiber on emulsified asphalt cold recycled mixture were studied from multi-scale. The effect of fiber on the macroscopic mechanical properties of emulsified asphalt cold recycled mixture was studied by early and molding strength, dry-wet splitting ratio test and fracture energy index of semi-circular bending specimen. Optimum fiber types and dosages for emulsified asphalt cold recycled mixes have been selected. The relationship between crack evolution and acoustic emission parameters activity of fiber emulsified asphalt cold recycled mixture is studied, which reflects the microscopic failure mechanism of the material. The microstructure and morphology of fibers in the mixture were observed by scanning electron microscopy (SEM). The results show that both fibers can improve the strength and crack resistance of emulsified asphalt cold recycled mixture. Basalt fiber has better adsorption and anchoring effect on asphalt due to its high modulus and rough surface texture. The optimum dosage is 0.3 % of the mixture quality. Fracture characteristics of fiber emulsified asphalt cold recycled mixture are reflected by acoustic emission parameters. At the optimum fiber content, the acoustic emission parameters showed that the time from micro-cracks to macro-cracks in the fiber-emulsified asphalt cold recycled mixture was 122.22% longer than that in the control group. Basalt fiber plays the role of reinforcing crack resistance and anchorage in emulsified asphalt mixture, delaying the expansion of micro cracks. [ABSTRACT FROM AUTHOR]

In this study, asphalt concrete specimens were subjected to a semicircle bending test at −10 °C to simulate the process of the development of cracks in asphalt concrete at low temperature. The acoustic emission parameters were collected during the test, the variation characteristics of acoustic emission parameters were analyzed, and the peakedness value was introduced to evaluate the damage of asphalt concrete. The dynamic evolution of fracture development was analyzed by periods with acoustic emission source location. The results indicate that the damage of asphalt mixtures shows an obvious brittle characteristic at low temperature, acoustic emission signals mainly originate from the crack damage caused by tensile stress, and the strength and number of signals can reflect the degree of crack development. Based on acoustic emission parameters and load curves, the cracking damage of asphalt concrete at low temperature in this study can be divided into three periods: a calm period, a stable development period, and a rapid fracture period. The crack point occurred and propagated upward rapidly in the rapid fracture period. During this period, acoustic emission parameters such as ringing count, acoustic emission energy, and amplitude increased suddenly; furthermore, the peakedness value reached its peak in this period and corresponded well with the low-temperature damage of asphalt concrete. Acoustic emission source location technology can track position of crack points and the propagation path of cracks, reflecting the dynamic evolution process of asphalt concrete crack damage at low temperature. [ABSTRACT FROM AUTHOR]

The self-healing properties of asphalt pavements reduce the need for frequent maintenance and repair of cracks and promote road sustainability. In this study, multiple healing tests were conducted under different healing conditions using the semicircular bending "crack-heal-crack" test. The beneficial effects of the healing temperatures and times were determined. However, below 60 °C, the healing index of asphalt mixture does not exceed 0.4. The peak healing indices of the 70# asphalt mixture in the fourth healing stage were 86% of the initial healing index. This correspond to the SBS# asphalt mixture parameters of 88%. Using the acoustic emission system, changes in the ring count and energy of the specimens before and after the healing were compared. The healing index of the cumulative ring count proposed in this study sufficiently correlates with that of the peak load. According to the three-dimensional time-difference positioning method, at the initial loading stage of the prehealing specimen, cracks first appeared at the top of the specimen in contact with the load, then concentrated near the prefabricated incision at the bottom, and finally expanded upward. When the specimen was loaded once again after healing, cracks mainly developed from the bottom upward. • The crack-healing ability of asphalt mixture was compared by acoustic emission system. • The peak healing indices of asphalt mixtures were higher than the fracture healing indices. • The healing of the asphalt mixture after forming macrocracks is significantly difficult. • The process of cracking and healing was analyzed according to 3D time difference localization method. [ABSTRACT FROM AUTHOR]