Study On Freeze-thaw Damage Characteristics Of Hot Recycled Asphalt Mixture With High Proportion Of Recycled Materials

China has done a lot of research on the road performance of recycled mixture,but the rap content is only less than 30%.The existing scholars have done a lot of research on the performance of recycled mixture with high proportion of rap content,including road performance and mechanical properties.Although they have done a more comprehensive and in-depth research,the research on the damage characteristics of recycled mixture with high proportion of rap content under freeze-thaw cycle is relatively less.Firstly,this paper studies the properties of recycled materials,and explores the performance damage characteristics of recycled mixture with high proportion of used materials under freeze-thaw cycles.Based on the recycling technical specifications,combined with the practical engineering experience and referring to the geographical environment characteristics of Liaoning Province,the single particle size aggregate is used for the new and old mineral aggregate,and the Marshall design method is used for mix proportion calculation to determine the optimal asphalt dosage.Secondly,uniaxial penetration test,low temperature splitting test and freeze-thaw splitting test are used to evaluate the decay law of high temperature,low temperature and water stability after freeze-thaw cycle.The test results show that the addition of rap can improve the high temperature performance of recycled asphalt mixture,reduce the low temperature performance and water stability.After adding recycled agent,the performance of aged asphalt and recycled asphalt mixture is obviously improved.Then,after repeated freeze-thaw cycles,the three kinds of road performance of recycled asphalt mixture with different contents are weakened.Comparing the three kinds of performance damage of recycled asphalt mixture after freeze-thaw cycle,it can be found that when rap content is 50%,the low temperature performance and water stability of recycled asphalt mixture are better than 60% and 70%,which can meet the requirements of pavement.Therefore,50% rap is the best content in the high proportion of old material.Finally,the damage degree of each performance index is fitted and calculated,and the correlation coefficient is above 0.96.Based on this,the freeze-thaw damage evolution model of rap hot recycled asphalt mixture is established,and the damage evolution law of rap hot recycled asphalt mixture under freeze-thaw cycle is explored.The model is used to analyze the practical significance of parameters of recycled asphalt mixture with different rap content after freeze-thaw cycle,discuss the influence of rap content on road performance of plant mixed hot recycled asphalt mixture,and determine the prediction method of freeze-thaw residual life of recycled asphalt mixture.