Research On Mesomechanics Model Of Asphalt Mixture Oxidative Aging

During the service period of pavement,asphalt mixture is undergoing traffic load and environmental impact,which leads to reduced durability of pavement.The oxidation of asphalt mixture is considered as one of the most important factors affecting the durability of pavement.So far,the chemical process of asphalt oxidation has been well characterized.However,the research on the oxidation mechanism of asphalt mixture based on the meso-structure is fairly limited.Aiming to improve the oxidation model of pavement structure based on oxygen diffusion reaction principle,and to understand the damage behavior and mechanism caused by oxidation more deeply,establishing the micromechanical model of oxidation of asphalt mixture is helpful for revealing the diffusion phenomenon of oxygen in the meso-structure of asphalt mixture,and inspection for the production and evolution of damage from the mesoscopic point of view.In this paper,a micromechanical model was established utilizing digital simulation and image processing methods to analyze the influence of void ratio on the oxidation of asphalt mixture based on the relationship between carbonyl area and viscoelastic properties of asphalt FAM phase.First,the long-term aging of asphalt pavement was simulated.Reactor oxidative aging method was used to obtain the actual mixture samples.A micro extraction method was proposed to extract asphalt,and its feasibility was proved by a series of asphalt experiments.The formation area of carbonyl in the aging process of asphalt at different moments was tested by Fourier Transform Infrared Reflection(FTIR),while the formation rate model of carbonyl was established based on chemical kinetics afterwards.The relationship between the area of carbonyl and the viscoelastic properties of FAM phase was studied with the help of DMA and DSR,so different linear viscoelastic properties can be assigned according to the area of the carbonyl in the FAM phase.The two-dimensional structure of asphalt mixture was reconstructed by image processing method.The diffusion of oxygen in asphalt mixture was simulated on the basis of Fick's second law,and then the material properties of FAM phase were assigned according to the area of carbonyl utilizing the result of diffusion.The influence of material mechanical properties on the overall mechanical response of asphalt mixture with the change of time was investigated.Compared with the results of the dynamic modulus of the virtual specimens,the void structure of the asphalt mixture had an important influence on the change of the mechanical properties of the oxidation products of FAM phase.The uncertainty of the modulus of the asphalt mixture depended on two main factors:(1)service time and(2)the property of the air void.In the future research,it is necessary to consider the change rule of void ratio with time in the model,which can better predict the oxidative aging behavior of asphalt pavement.