Research On The Key Technologies Of High Performance Recycled Asphalt Pavement With High Reclaimed Asphalt Pavement Content

Hot in-plant recycling is the most widely used renewable technology in road engineering,but the content of reclaimed asphalt pavement(RAP)is usually low,so the regeneration economic efficiency and effectiveness of hot in-plant recycling are affected.Besides,there's a lack of corresponding theoretical basis and guidance of design and construction of hot in-plant recycling asphalt mixture with high RAP content.This paper analyzed the deficiencies in the corresponding research on hot in-plant recycling and studied the key technologies in the process of hot in-plant recycling with high RAP content.Firstly,the law of asphalt aging and rejuvenating was analyzed through a large number of indoor simulation tests,and it was found that the penetration and ductility of bitumen were dropping and the softening point and viscosity were raising while the aging was growing on.In contrast,the addition of asphalt rejuvenate agent would reduce the viscosity of the aged bitumen and restore its rheology.Then,the mechanism of asphalt aging and rejuvenating were studied at the micro level based on the atomic force microscope.The result of the research showed that the light component of asphalt was greatly reduced in the aging process while the internal component structure of asphalt did not change after the regeneration.Secondly,according to the deficiency of evaluation methods of asphalt rejuvenate agent,the paper put forward a new method using asphalt mortar to evaluate the asphalt rejuvenate agent and designed different methods for sample preparation,which simulated different diffusion conditions of asphalt rejuvenate agent.The feasibility of this method was then verified by experiment.On the basis of this evaluation method,this paper further gave a complete process to determine the optimum amount of the asphalt rejuvenate agent and the method for the comparison of the asphalt rejuvenate agent.Thirdly,the paper studied the influence of variability of high RAP content on the optimum asphalt aggregate ratio,material temperature,paving temperature,gradation segregation and temperature segregation etc.of the recycled asphalt mixture through indoor simulation experiment and theoretical research.The results revealed the problems and effects of variability of high RAP content in production and construction of recycled asphalt mixture and provided some guidance for the construction of hot in-plant recycling with high RAP content.Finally,aiming at the problem of performance variation caused by the variability of RAP grading,the paper took control of 4.75mm sieve rates to the upper limit to reduce the effects of variability of RAP on the mixture performance,on the basis of the strength composition principle of recycled asphalt mixture.The mixture performance test verified the superiority of the design method and the method provided a reference for the designing of high performance recycled asphalt mixture with high RAP content.