Research On Interface Strength Mechanism Of Emulsified Asphalt Cold Reclaimed Mixture

Considering the complicated structure and component in emulsified asphalt and cement cold reclaimed mixture,this paper started with four different mixing orders: mixing RAP with cement first and then adding emulsion;mixing RAP with emulsion first and then adding cement;mixing RAP,cement and emulsion at once;mixing cement and emulsion first and then adding RAP(order A to D).The crystallite composition and micro-morphology,microstructure and properties of the components are studied through a series of experiments.The main work of the thesis includes the following aspects:Firstly,this paper started with the macroscopic strength and performance of cold reclaimed mixture,by evaluating the indexes of the splitting strength,dry-wet splitting strength ratio,dynamic resilient modulus and dynamic modulus of the cold recycled mixture under four different mixing orders.The results showed that the mechanical properties of the cold reclaimed mixture under different mixing orders are quite different.The overall performance of mixing order D and B is better than mixing order A and C.Then,this paper focused on composing materials affecting the cold reclaimed mixture strength.It was found that the reclaimed asphalt pavement materials have a deeper interaction with the asphalt emulsion than the virgin aggregate,in which virgin asphalt and old asphalt begin to form the new effective binder that is essentially associated with the second phase of the curing and further cohesion build-up of recycled mixtures.Secondly,the distribution characteristics of two-phase materials,(cement with virgin aggregates,cement with RAP materials,asphalt with virgin aggregates,and asphalt with RAP materials)are studied by scanning electron microscopy with backscattering observation technology and digital image processing.The gray threshold segmentation can effectively segment each phase products.Cluster analysis,Weibull distribution and sensitivity analysis were used to analyze the characteristics of voids,fillers and binders of two-phase materials,and the interface transition zone between the void content and the cement hydration products,and the old asphalt content.The thickness of the interface zone of the two-phase material differed: asphalt with virgin aggregates < asphalt with RAP materials < cement with virgin aggregates <cement with RAP materials.Finally,the differences in the micro-morphology of the pure mortar and the mortar in mixture were compared respectively.Then,the difference of the topographical characteristics and the difference of the material composition of the cold reclaimed mixture under different mixing orders were compared.According to the results of energy spectrum analysis,the layered mortar in each mixing order were existent and dispersed phases of cement,asphalt and filler.The point lies in the difference in the relative content of cement and asphalt,and the composition of cement asphalt.The internal mechanism,of which the mixing order B and D is better than the mixing order A and C,is that the thicker main phase of asphalt in transition zone is not conducive to interfacial bonding,and the pre-mixing of asphalt and cement is beneficial for the mortar to form effective compound binder.