Mix Design And Performance Research On Soft BRA Modified Hot Recycled Asphalt Mixture

Soft Buton rock asphalt(BRA)contains more light components such as diesel oil etc.,and its softening point and high temperature performance are relatively lower.Other performances are similar to those of hard BRA.These light components can be used as an excellent regeneration agent.The incorporation of soft BRA into reclaimed asphalt pavement(RAP)can play a role in softening aging asphalt,improving compatibility and improving pavement performance etc.However,at present,there is still a lack of in-depth research in this area at home and abroad.Therefore,in this thesis,soft BRA is used as a regeneration agent,and AC-20C in the middle surface layer is used as the research object to carry out the research on mix design and pavement performance for soft BRA modified hot recycled asphalt mixture,so as to provide a new type of green regeneration technology for asphalt regeneration.1)The performances of raw materials used in soft BRA modified hot recycled asphalt mixture were tested,including coarse aggregate,fine aggregate,mineral powder,A-70#matrix asphalt,soft BRA and RAP etc.which meet the technical requirements of the specifications.2)The mix design and test of modified hot recycled asphalt mixture with five different soft BRA contents(1%～5%)and five different RAP contents(10%～50%)were carried out based on response surface optimization method.The results show that with the increase of soft BRA and RAP contents,the optimum oil-stone ratio of the mixture increases,and the actual oil-stone ratio of the matrix asphalt decreases.However,the variation of the optimum oil-stone ratio is gentler than that of the matrix asphalt,and the difference between the two increases from 0.72%to 3.59%.It indicates that the higher the contents of soft BRA and RAP are,the more the content of matrix asphalt is reduced,that is,the asphalt in soft BRA and RAP plays the role of binder.In order to ensure a reasonable amount of matrix asphalt and the mixture performance,the optimal content of soft BRA is determined to be 3%.3)The pavement performance tests of five kinds of modified hot recycled asphalt mixture with different RAP contents(10%～50%)under 3%soft BRA content were carried out.The results show that the higher the RAP content,the better the high-temperature stability.When the RAP content is less than 30%,the lower the content,the better the low-temperature performance.When the RAP content is 30%,the water stability is the best.When the RAP content is 20%,the dynamic moduli at high and low temperatures are the best,and the viscoelasticity and deformation resistance are the best.The impermeability and skid resistance of the mixture with all RAP contents meet the specification requirements.Accordingly,the suitable content range of RAP is determined as 10%～30%.4)By analyzing and evaluating the technical feasibility and economic,social and environmental benefits for soft BRA modified hot recycled asphalt mixture,the technology meets the requirements of low carbon and environmental protection,and has high performance price ratio.In summary,the soft BRA as a regeneration agent for RAP modification and hot recycled proposed in this thesis is technically feasible and economically reasonable,and the research results can provide reference for its popularization and application.