Research On Performance Of Recycled Asphalt Mixture Based On Degree Of Miscibility

The plant hot recycling technology is widely used in the recycling of waste asphalt mixture（RAP）because of its stable quality and simple construction.It can effectively reduce construction costs and environmental load,and have significant social and economic benefits.However,there is a"black rock effect"in the production process of recycled asphalt mixtures,and it is difficult to completely peel off from the aggregate surface,this will result in an increase in the amount of virgin asphalt added during the mixing process;However,the virgin asphalt and the aged asphalt will be further miscible during use,which will cause the effective asphalt content of the mixture to exceed the optimal value and early disease.Therefore,it is very important for the quality control of the recycled asphalt mixture to find out the degree of miscibility of the virgin and aged asphalt and optimize the mix ratio design of the recycled asphalt mixture.In this paper,four kinds of regenerants are used to prepare regenerated asphalt,the effect of regenerating agents on the performance of aged asphalt is compared,the type of regenerating agent is optimized,and the optimal content is determined,and analyzes the wetting behavior of the regenerant on the surface of the aged asphalt,and studies the effect of temperature on the wetting speed of the regenerant-aged asphalt interface;Through the aging of the regenerated asphalt in a rotating film oven for different lengths,the effect of the regenerant on the thermal aging performance of the asphalt was studied,and use infrared spectroscopy to quantitatively analyze the growth rate of the functional group index of the regenerant-aged asphalt to evaluate the thermal stability of the regenerated asphalt;Carry out the regenerating agent-aged asphalt diffusion test that simulates the high temperature environment of road surface and transportation high temperature environment at 60℃and160℃,and analyze the diffusion efficiency of different oil-based regenerants in the asphalt layer.Based on"complete miscibility",the mix ratio design of recycled asphalt mixture（RAM）is carried out,and determine the best asphalt dosage for"partially miscible"recycled asphalt mixture;The optimal asphalt dosage was revised through"invalid asphalt dosage",and the process for determining the optimal asphalt dosage of RAM mix ratio was proposed and verified by road performance.By designing an ₃³orthogonal test to analyze the factors affecting the degree of miscibility of recycled asphalt,and studied the effects of RAP content,mixing temperature and dry mixing time on the degree of miscibility and porosity,and optimized the best mixing plan.Finally,the research results of this paper are verified by physical engineering.Research indicates:the ketone-carbonyl-containing bio-oil-based regenerant A（SRA）has the best recovery effect on the performance of aged asphalt;SRA has the best wetting performance on the surface of old asphalt at 130°C,and its surface adhesion work increases with the increase of the regenerant content;When SRA is mixed with aged asphalt,the growth rate of its carbonyl functional group index CI decreases,which improves the thermal stability of recycled asphalt;The effective ratio of the aged asphalt has a linear fitting relationship with the index of the carbonyl and sulfoxide functional groups in the recycled asphalt.Through simulation experiments and calculations,the amount of invalid asphalt in the RAM with 50%RAP content is 0.51%,and the optimal asphalt content is 4.79%after the B2 modification of the simulated transportation process;After modifying the amount of"partially miscible"RAM asphalt,its high temperature stability is increased,low temperature crack resistance and water stability are reduced,but they all meet the requirements of the specification.The significant effects of different factors on the miscibility of virgin and aged asphalt are as follows:RAP content>mixing temperature>dry mixing time;Combining the influence of different factors on the miscibility of the mixture and the amount of invalid asphalt,the optimal mixing plan is obtained as follows:40%RAP content,165℃mixing temperature and 90s dry mixing time.The physical engineering shows that the recycled asphalt mixture designed based on the"degree of miscibility"has a reasonable material composition and good road performance.