Study On High Modulus Design Theory And Performance Of Recycled Asphalt Mixture With Large Amount Of RAP

The traditional regeneration technique is to use organic rejuvenators to recover the performance of aged asphalt by softing it.Its disadvantage is that the amount of recycling asphalt pavement(RAP)is low.In this paper,the technical route of high modulus design concept for asphalt pavement recycling is proposed.In this technical route,the characteristics of hard asphalt and fine aggregate of RAP are fully utilized.By adopting the design concept of high modulus asphalt mixture,the recycling of large amount of RAP can be realized,and the performance and service life of the recycled pavement are improved.Firstly,the existing design method for hot-mix recycled asphalt mixture and design method and performance of high modulus asphalt mixture were studied.It is pointed out that fine gradation and hard asphalt are common to RAP and high modulus asphalt mixture,and provides a theoretical basis for high modulus design of recycled asphalt mixture with regeneration of large amount of RAP.Through the analysis of a large number of engineering examples across the country,it is found that RAP gradation has good stability and uniformity,and its gradation does not change significantly with the region and service life.This paper defines it as the inherent value of RAP gradation.In view of the fact that most of the RAP is in the form of agglomeration in the reclaimed asphalt mixture,the agglomeration condition of RAP is studied.The composition state of clusters of RAP and its effect on the performance of recycled asphalt mixture were clarified.In this paper,the experiment of water film thickness is designed to test the distribution of asphalt film on aggregate surface.The research results show that the asphalt film on the aggregate surface is not uniformly distributed,and the asphalt film thickness can differ by as much as 7 times on the surface of particles with different sizes.At the same time,the thickness of the asphalt film on the surface of clusters of RAP with different sizes was determined.The compatibility of hard asphalt used in high modulus asphalt mixtures and aged asphalt was studied,and the similarity of penetration of aged asphalt was proposed as the standard for preparing hard asphalt.By utilizing the characteristics of RAP,including fine gradation and hard asphalt,and the preparation and use of hard asphalt,a high modulus design method of recycled asphalt mixture with regeneration of large amount of RAP is established.Based on the EME gradation and inherent value of RAP gradation,the gradation range of the large amount of recycled asphalt mixture was determined.The calculation method of asphalt content based on the composition state of clusters of RAP is given.The test results show that under the condition of 50%～100%RAP content,the high temperature performance and low temperature performance of recycled asphalt mixture can all be achieved through high modulus design.Its high and low temperature performance and anti-fatigue performance are better than the AC20 mixture using new asphalt,realizing the unity of large amount of RAP and high performance.