Multi-scale Characterization Of Self-healing Behaviors Of Asphalt Material Damage And Its Acoustic Emission Diagnosis

Asphalt mixture is a kind of complex multi-phase composite materials and its selfhealing ability has an important impact on the service life of asphalt pavement.Due to the lack of effective methods for studying the damage and self-healing behavior of asphalt mixture,the objective of paper was to reveal the self-healing mechanism of asphalt damage from a multi-scale perspective and perceive the damage and self-healing evolution of materials by using the acoustic emission(AE)technology.In this paper,the AE nondestructive technology was used to dynamically diagnose the damage mode of asphalt mixture and perceive its self-healing behavior.Firstly,through the multi-scale method,the rheological behavior and fracture surface morphology of asphalt material were discussed to investigate its inherent healing mechanism and to quantify its damage self-healing ability.Secondly,by establishing a specific device,the adhesive failure tests and cohesive failure tests of asphalt mixtures were carried out to explore the AE characteristics of different damage modes.Thirdly,the AE signals were classified by combining K-means and SVM method to realize the accurate diagnosis and recognition of damage modes of asphalt mixture.Finally,the AE parameters were utilized to characterize the damage self-healing behavior of asphalt mixture,the cumulative energy parameters were used to build the evaluation index of damage self-healing performance of asphalt mixture,and the influence of temperature was discussed.The result shows that the self-healing ability of asphalt binder could be given full play at the softening point,in the stage of microcrack generation and propagation.Once entering the macro failure stage,the mechanical properties of asphalt binder could not be fully recovered with the increase of temperature.The self-healing index established by dissipation energy can effectively evaluate the damage self-healing performance of asphalt binder.The damage evolution process of asphalt mixture could be divided into the initial damage stage in which the damage of asphalt aggregate interface and the damage of cement occur at the same time,the crack concentration and expansion stage in which the damage of asphalt aggregate interface dominates,and the macro fracture stage in which the damage of stone dominates.The AE felicity effect can well reflect the damage self-healing behavior of asphalt mixture.The better the damage self-healing performance is,the more significant the felicity effect is.The cumulative energy ratio of AE can be used to evaluate the damage selfhealing performance of asphalt mixture.The study focuses on diagnosing the damage evolution process and quantitatively evaluating the self-healing property of asphalt material by using AE technology,which achieves the integration of microscopic,mesoscopic and macroscopic researches for asphalt materials and would have important academic significance and practical value.