Mix Design And Pavement Performance Study Of Layered Recycled Asphalt Mixture

At present,China has the world’s first freeway mileage.As a result of Pavement Renovation and maintenance,a large number of waste pavement materials(RAP materials)will be produced every year.Discarding these RAP materials will not only cause damage to the natural environment,but also a great waste of resources.The problem can be solved by using recycled asphalt mixture technology to treat RAP materials.However,the application technology of recycled asphalt mixtures in China is still immature,lacking perfect RAP material management system,ignoring the influence of RAP variability on the road performance of recycled asphalt mixtures,resulting in low RAP mixing ratio and instability of road performance of recycled asphalt mixtures.In this paper,the method of stratified recycling is used to control the variability of RAP material,and on this basis,research is carried out.The main research and work contents are as follows:Firstly,large pieces of waste pavement material are treated by artificial layered crushing to avoid the damage of milling process to the old aggregate;the influence of current old asphalt recycling methods on the performance of recycled asphalt is analyzed,and the old asphalt is recycled by vacuum filtration method and improved Aberson method,avoiding the influence of recycling process on the performance of recycled asphalt;and the influence of layered recycling and one-time recycling on the performance of recycled asphalt The influence of RAP asphalt-aggregate ratio,gradation and asphalt aging degree variability is analyzed.It is concluded that stratified recovery can effectively control RAP asphalt variability.The asphalt-aggregate ratio,gradation,old aggregate properties and asphalt properties of RAP asphalt in different layers are tested.It is concluded that layered recycling can effectively control the variability of RAP.The experiments on the oil-stone ratio,gradation,properties of old aggregate and asphalt properties of different layers of RAP are carried out.It is concluded that both the upper RAP and the lower RAP have undergone serious aging,and the aging degree of the upper RAP is more serious.Moreover,On the basis of previous studies,the aging and regeneration mechanism of RAP was analyzed,and the optimum dosage of regenerant was determined according to the viscosities of old asphalt and regenerant,and the regenerant was added by spraying with high pressure cylinder.The mixing process of regenerated asphalt mixture was studied,and the fusion degree of new and old asphalt was analyzed by preheating temperature,preheating time and mixing temperature.Influenced by different factors,the optimum preheating temperature > preheating time > mixing temperature,and the optimum mixing degree of old and new asphalt are as follows: preheating temperature110 C,preheating time 4 h,mixing temperature 180.Marshall design method was used to design the mix proportion of RAP mixture with different layers at different mixing ratios(0%,20%,30%,40%).In the last,the pavement performance test of recycled asphalt mixture was carried out after determining the mix ratio of different mix ratios.The test found that the addition of RAP can improve the high temperature performance of recycled asphalt mixture,but reduce the low temperature crack resistance and water stability performance;there are significant differences in the pavement performance of recycled asphalt mixture with different layers of RAP;and the pavement performance of RAP mixture was analyzed.Sensitivity: high temperature stability sensitivity > low temperature crack resistance sensitivity > water stability sensitivity.