Experimental Study On Fatigue And Fracture Properties Of Emulsified Asphalt Cold Recycled Mixture Under Bending Load

The cracking problem of emulsified asphalt cold recycled pavement seriously restricts its use.In order to understand the reasons that affect the cracking of the emulsified asphalt cold recycled mixture,the fatigue and fracture properties of it under bending load were studied in this paper.Firstly,making research plans of this paper by the current research situation at home and abroad.Three kinds of cold recycled mixtures,including ordinary emulsified asphalt,SBR modified emulsified asphalt,and externally mixed basalt fiber was selected,and the mixing ratio design was completed.Then the four-point bending strength test of beams with prefabricated cracks,the four-point bending fatigue test of beams without prefabricated cracks,and the acoustic emission test.The fracture mechanics method evaluated the fracture properties of three cold recycled mixtures.The fatigue properties of three cold recycled mixtures were analyzed by phenomenological theory and energy analysis method,and the acoustic emission parameters were analyzed by characterization parameter analysis method.Finally,a scanning electron microscope(SEM)was used to explain the influence of the micro-morphology of the mixture on the macro-mechanical properties from a microscopic point of view.The test results show that SBR-modified emulsified asphalt and the addition of basalt fiber can effectively improve the fatigue resistance and fracture resistance of cold recycled mixture and reduce the risk of cracking.The fracture of emulsified asphalt cold recycled mixture mainly occurs at the interface between asphalt mortar and fine aggregate.SEM test results show that the interfacial performance can be improved by adding fiber.The calculation results of dynamic modulus show that for the same kind of cold recycled mixture,the attenuation degree of dynamic modulus at failure has little relationship with the stress level but is closely related to the type of cold recycled mixture.SBR modified emulsified asphalt and externally mixed basalt fiber improve the average dissipated energy of emulsified asphalt cold recycled mixture during a single fatigue cycle in the fatigue test.Acoustic emission parameters can better characterize the fatigue test process and fracture performance of emulsified asphalt cold recycled mixture.This paper has particular reference significance for improving the crack resistance design of cold recycled mixture and promoting the application of acoustic emission technology in asphalt mixture research.