Study On Constitutive Model Of Asphalt-Aggregate Interface And Mesomechanics Based Mixture Viscoelastic Creep Performance

Asphalt mixture is one of the most important road construction materials,which consists of aggregate,asphalt,void and asphalt-aggregate interface.The asphalt-aggregate interface is often considered as the weakest link in asphalt mixtures with respect to its deformation,strength and durability.The study took the asphalt-aggregate interface system as the main research object.Firstly,based on the self-design interface testing system,we conducted an investigation on the influence of different factors,including aggregate surface roughness,asphalt binder aging,temperature,loading rate,aggregate types,etc.,on the asphalt-aggregate interface by means of oblique shear tests and direct shear tests.The results suggest that it should consider both the strength index and energy index to better evaluate the asphalt-aggregate interface performance.Secondly,the interface bonding failure process was quantitatively sensed by the testing system to establish an asphalt-aggregate interface bond-slip constitutive model.The grey relational analysis(GRA)has been successfully used to identify the significant factors that affect the constitutive model parameters.It was shown that the aging is of the most important factor,followed by the loading rate,temperature,normal stress and the aggregate roughness.Finally,based on the bond-slip constitutive model of asphalt-aggregate interface,a meso-scale finite element model of asphalt mixture that consider interfacial effect was established.The numerical simulation of the three-point beam creep test was carried out and verified by the laboratory test results.Furthermore,a series of factors,including the gradation,angular and elastic modulus of coarse aggregate,void ratio and asphalt-aggregate interface parameters etc.,were considered to investigate the influence on the mechanical behavior of asphalt mixtures.The results indicated that the higher interfacial fracture energy and bonding strength are,the better resistance to interfacial crack and permanent deformation of asphalt mixtures.The creep performance of medium gradation asphalt mixtures was better than that of fine-grained asphalt mixtures,the larger the angular index of coarse aggregate was,the better ability of asphalt mixture to resist deformation.As to the suspended dense structure asphalt mixtures,with the increase of void ratio,the creep deformation increase gradually,and the excessive void ratio would lead to the fracture of the interface.The results of the study depict the whole failure process of asphalt-aggregate interface damage on meso-scale mechanics,which could provide a theoretical support for the complex mechanical analysis of asphalt mixtures,and would hopefully give an insight into the understanding of the failure behaviors of an asphalt-aggregate interface in support of the optimization design of asphalt mixtures with highly academic significance and practical value.