Experimental Research On The Performance Of High Content RAP Thermal Recycling Material

In recent years,highway construction in our country is developing rapidly.In the current pavement forms,asphalt pavement occupies a considerable proportion,especially for high-grade highways,more than 90%of which are asphalt pavement forms.With the advent of the maintenance and repair stage,a large number of waste asphalt pavement materials(RAP)are produced,and the research on the regeneration technology of waste asphalt mixture is the general trend.However,in the regeneration process,a small amount of RAP can no longer solve the growing problem of recycled RAP materials.The low utilization rate of recycled RAP materials leads to insignificant benefits of recycled mixtures.Therefore,this article has carried out research on the application of high RAP content in asphalt mixtures.This article focuses on the application technology of recycled asphalt mixture with high RAP content in the laboratory.Starting from the performance evaluation of RAP,study the characteristics of RAP material and the effect of additives on the performance improvement of old asphalt.On this basis,the key production process,mixture composition design and road performance evaluation of high RAP content hot reclaimed asphalt mixture are carried out.The main results are as follows.(1)This article analyzes the mechanism of asphalt aging.Based on the research of asphalt aging mechanism,the RAP old material was extracted and analyzed,and the RAP gradation,moisture content,old asphalt performance,old aggregate performance,etc.were evaluated and studied.Through asphalt shear rheology test and performance index test,the effect of regenerating agent and Sasobit REDUX additive on the performance of new and old asphalt was studied.It was determined that the regenerant content was 10%and the content of Sasobit REDUX was 3%.(2)Research and discussion are carried out around the key production processes in the thermal regeneration process,focusing on the control of the heating temperature of the RAP material and the new aggregate in the thermal regeneration process,and the optimal output of the recycled mixture after adding Sasobit REDUX has been determined.Determine the best preheating temperature for newly added mineral materials and RAP materials.The experiment analyzed the effects of mixing time and the order of addition of various materials during the regeneration process on the production quality of high-volume RAP hot-recycled asphalt mixtures.The optimal combination of the regeneration process is determined by the gray ratio analysis method:RAP material mixing;Sasobit REDUX is mixed with asphalt first;the total mixing time is 180s.(3)On the basis of the performance evaluation research of RAP material,new asphalt,new aggregate,Sasobit REDUX additive and regenerating agent,the Marshall volume design method was used to carry out 40%,50%,60%,70%The mix ratio design of the recycled asphalt mixture with RAP content determines the optimal asphalt content.The aggregate clearance ratio and asphalt saturation of the recycled asphalt mixture with 70%RAP content are beyond the range required by the specification,while the Marshall indicators are all qualified under other content.(4)Through laboratory tests,the high-temperature stability,water stability and low-temperature cracking resistance of recycled asphalt mixtures with high RAP content were studied.The results show that with the increase of the amount of RAP,the dynamic stability and freeze-thaw splitting strength ratio gradually decrease,and the bending failure strain gradually increases.After adding RAP,the high temperature stability and water damage resistance of the mixture have decreased,while the ability to resist cracking damage has been improved.The designed 40%-70%RAP content of the recycled mixture can meet the requirements for various road performances.