Micromechanical Model Of RAP Hot Regeneration Mixture And Analysis Of Influencing Factors Of Modulus

In recent years,with the country's attention to the construction of environmentally friendly and resource-saving society,the recycling and utilization of materials has become the focus of attention of all industries,also Thermal Regeneration Technology of Pavement with some RAP added into asphalt mixture has become a hot spot of pavement maintenance.Although RA can restore the performance of aged asphalt,as a result that the content of RAP mixed with RA can be increased in bituminous mixture,the utilization rate of recycled materials is still low.At present,there are still a lack of regenerative agent mixing amount and health conditions of the reference standard,to ensure that the performance of RAP hot regenerative mixture meet the design requirements.Therefore it not only can improve the reuse of resource efficiency,protect the environment and is of great significance of asphalt mixture proportion design and construction to establish the micromechanical model of RAP mixture,estimate the response parameters of RAP mixture through the micromechanical model,and analyze the influence rule of RA dosage and other factors on the modulus.This paper has done a lot of theoretical derivation and experiments.Firstly,based on the four-phase model in the micromechanics of composite materials,a two-dimensional four-phase model of single aggregate inclusion in the shape of sphere,ellipsoid and rectangle in RAP mixture was constructed.Based on the four-phase model of single aggregate inclusion,the two-dimensional microstructure of RAP mixture in the shape of sphere under the four-layer embedded system with the voids in RAP mixture was established.Some formulas was got from the relations with basic properties of the layers of material on the basis of the relationship between stress and strain in viscoelasticity,boundary continuity conditions,strain energy consumption in macroscopic and microscopic,so the micromechanical model of asphalt mixture under the two-layer embedded system was derived,and then the micromechanical model under the three-layer embedded system was derived.Finally,the micromechanical model of RAP mixture under the four-layer embedded system was obtained.It is found that the modulus of recycled asphalt layer was the main influencing parameter of the modulus of RAP mixture.Secondly,in order to analyze the influence of RA incorporation ratio,health condition and other factors on the modulus of recycled asphalt through the modulus changes of different recycled asphalt test groups,Brinell Viscometer,Dynamic Shear Rheometer method and Three-point Bending of asphalt trabeculae were used to study the variation rules of viscosity,viscoelastic parameters and stiffness modulus of recycled asphalt.Also based on sandwich beam theory,the influence of diffusion characteristics of regenerator and aging efficiency of regenerated asphalt on modulus was analyzed with the "Sandwich recycled asphalt trabeculae" which was prepared to simulate the diffusion process of RA.Finally,to verify the influence parameters of modulus,uniaxial compression dynamic modulus test and trabeculae three-point bending test were used to explore the change trend and change ratio of RAP mixture modulus.In the research,the relation between the response parameters and microstructure of the mixture was established,the construction process of micromechanical model of RAP mixture was described,the influence of the ratio of RA and health condition on the modulus of recycled asphalt was studied,the influence trend of recycled asphalt layer on the overall modulus of asphalt mixture was analyzed.Which can provide the basis for RAP mixture design and is helpful to study the diffusion characteristics of regenerant.