Research On Performance Of Cold Recycled Asphalt Mixture Based On Variability Of RAP Material

The recycling of RAP(Reclaimed Asphalt Pavement)material has a positive significance for the construction of resource-saving and environment-friendly transportation industry.While improving the utilization rate of RAP materials,it is an important research content to improve the large deviation between the design results of the current recycled materials and the actual performance.As one of the important components of recycled materials,RAP materials may come from different bid sections of the same project or different structural layers of the same bid section.Even the same structural layer may have different maintenance processes,construction materials,etc.The complexity of its source will inevitably lead to many difficulties in the design of cold recycled materials,which affects the representativeness of the design results of the single-graded mix ratio.According to the existing design methods of cold recycled asphalt mixture,it is necessary to explore the fluctuation range of recycled material performance by increasing the workload of material design,or it may bring about a dilemma that the result of material design is less representative.Numerical simulation test methods provide new ideas for solving the above-mentioned problems.Virtual mechanical tests can be used to explore the impact of different factors on the performance of recycled materials.Based on this,this article analyzes the different RAP materials,and designs a test plan to explore the impact of different factor variations on the performance of recycled materials;Establish a numerical simulation model to simulate the virtual splitting test,explore the stress distribution and change law of the model under different factor levels,and provide a reference for the material design stage of recycled materials.First,relying on the reconstruction and expansion project of the Yangmao section of the Shen Hai Expressway,the original pavement structure was milled layer by layer,and the main aspects of the variability were explored through the performance research of the pavement recycled materials at different levels.Design test plans to explore the influence of different factors on the performance of recycled materials.The results show that: When the gradation changes,the splitting strength and dynamic stability of the recycled asphalt mixture will decrease with the increase of the content of the fine RAP material,and the dynamic stability will deepen and increase with the aging degree of the old asphalt.The increase in the content of old asphalt is conducive to improving the water stability of recycled materials.The content and properties of old asphalt in RAP will affect the performance of recycled materials and should be considered in the material design stage.With the increase of RAP content,the splitting strength,high temperature stability,and water stability of recycled materials gradually decrease.In the material design stage,the content of RAP should be controlled reasonably to ensure that the performance of recycled materials meets the specification requirements.Secondly,based on CT scanning and digital image processing technology,establish the finite element numerical simulation model;Using computerized aggregate random placement algorithm program to randomly generate aggregates and voids in a specific model area through the program algorithm,which greatly improves the model generation speed while effectively controlling the aggregate content of each grade of particle size.The cohesive model is used to simulate the stress action at the interface between aggregate and mortar and inside the mortar,and the Burgers model is used to characterize the viscoelastic properties of asphalt mortar.The results of the uniaxial static load creep test are used to fit the model parameters.The results show that the parameter fitting results are close to the real situation,and the Burgers model can simulate the viscoelastic properties of asphalt mortar well.Finally,a virtual split test simulation was carried out on the numerical simulation model to explore the influence of different factor variations on the performance of recycled materials.Research indicates: The random model generated by the aggregate placement can replace the real CT model for virtual simulation analysis to a certain extent.During the splitting process,the specimen appears to be compressed at both ends and tensioned in the middle,and the compressive stress is much greater than the tensile stress.The overall performance on the horizontal axis is tensile stress,and the distribution presents the characteristics of small left and right ends,and large tensile stress near the middle position,so the splitting failure of the test piece mostly occurs from the middle position inside the test piece.Variations of different factors have different effects on the internal stress distribution of the model,which indicating that the macroscopic properties of recycled materials are affected by the microscopic structure performance.