| Waste rubber tire modified bitumen can not only enhance the road performance of virgin bitumen,but also effectively mitigate the pollution of waste rubber tires,which has great economic and environmental benefits.However,the significant physicochemical property differences between the rubber powder of waste rubber tires and the bitumen matrix cause the poor storage stability of the modified bitumen and limit the development and application of rubber powder modified bitumen.The compatibility of modified bitumen originates from the interaction between the modifier and bitumen,but the interaction mechanism between rubber powder and bitumen matrix is not well understood.In this study,the performance evaluation index of waste rubber tire modified bitumen was proposed using the gray correlation method,and the interaction mechanism between waste rubber tire rubber powder and bitumen matrix was explored using molecular dynamics simulation,microscopic morphology observation and rheological performance test.The main contents of this study are as follows.Firstly,the applicability of the current bitumen road performance index system to the waste rubber tire rubber powder modified bitumen is utilized,the correlation between the indexes is analyzed,and the engineering performance technical indexes of rubber powder modified bitumen are proposed.On this basis,the effects of modified bitumen preparation temperature,mixing method and storage method on the needle penetration,ductility,softening point,viscosity and microscopic morphology of modified bitumen were systematically evaluated in order to derive a modified bitumen preparation scheme applicable to actual projects.The results show that the more excellent rubber powder modified bitumen preparation method is: the temperature is 180 ?,the method uses the shear method,in order to prevent aging,at most allow repeated heating once,the storage time should not exceed 4hours.In addition,rubber powder optimum admixture of 17%,the best mesh is 40 mesh,with the development of time,the greater the dissolution volume of rubber powder.Second,samples of waste rubber tire modified bitumen were prepared and systematically evaluated for fatigue resistance,crack resistance,shear deformation resistance,and rutting resistance.Fourier transform infrared spectroscopy and fluorescence microscopy were used to evaluate the microscopic morphology and modification type of rubber powder in bitumen matrix.Finally,the molecular model of the assembly method of bitumen was constructed,and the optimal polymerization degree of molecular simulation of natural rubber was obtained using solubility parameters,and the system models of matrix bitumen and scrap rubber tire modified bitumen were further obtained.The four-component content of the model and the glass transition temperature were calculated,and the results showed the correctness of the model.The interaction mechanism between the scrap tire and bitumen matrix was studied,and the binding energy and diffusion coefficient were calculated,and the results showed that the binding energy of scrap tire and bitumen four-component ranking is: aromatic > saturate >resin > asphaltene.When the scrap rubber tire is added to the bitumen matrix,it will adsorb the non-polar components(saturate and aromatic)and swell,and the movement of bitumen molecules will be limited.The non-polar molecules form a transition interface between the scrap tire and the bitumen matrix and transition the good elasticity of the scrap tire to the bitumen matrix. |
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