Study On Quality Control And Application Technology Of Hot Recycling Asphalt Mixture

With the continuous increase of highway maintenance mileage in China,a large number of waste asphalt mixture(RAP)produced in the process of road maintenance and reconstruction need to be processed.It is an effective method to reuse RAP by plant-mixed hot recycling technology.However,there are still many problems in the application of plant-mixed hot recycling asphalt mixture in China.RAP sampling is relatively random,which leads to insufficient representativeness of samples and cannot reflect the real situation of the pile,thereby affecting the accuracy of mix design results of plant-mixed hot recycled asphalt mixture.In addition,the production process has a great influence on the performance of plant-mixed hot recycled asphalt mixture,which is easy to lead to unstable quality and performance of recycled asphalt mixture.Therefore,it is of great practical significance to carry out research on quality control measures such as reclaiming method,mix proportion design and production process for plant hot recycled asphalt mixture to improve RAP utilization rate,improve road performance of plant hot recycled asphalt mixture and promote its engineering application.This paper relies on the G206 overhaul project in Yantai City,Shandong Province.Firstly,the RAP material piles are pretreated by crushing,screening,transportation and stacking.Representative samples are collected from the graded RAP material piles(10-20 mm and 0-10mm)by bulk sampling method and bulk sampling method,respectively.The variability of RAP under the two sampling methods is compared and analyzed by RAP asphalt content and mineral grading index,and a more scientific RAP sampling method is proposed.The results show that the variability of asphalt content and the variability of mineral aggregate gradation of the material taken by the heap sampling method are smaller than those of the whole heap sampling method.The material taken by the heap sampling method can improve the uniformity of RAP,which can better represent the actual situation of RAP heap.Then,based on the RAP samples of the whole heap sampling method and the heap sampling method,the Marshall design method was used to carry out the mix proportion design and road performance research of the plant-mixed hot recycled asphalt mixture with different RAP contents.The effects of the two sampling methods and RAP content on the road performance of the plant-mixed hot recycled asphalt mixture were compared and analyzed.The results show that under the same RAP content,the low temperature crack resistance and water stability of hot recycled asphalt mixture prepared by bulk sampling RAP are significantly better than those prepared by bulk sampling RAP.Then,on the basis of RAP content of 20 %,the influence of different mixing temperature,mixing time,mixing sequence,dry mixing time and storage time on the road performance of plant-mixed hot recycled asphalt mixture is studied.According to the fuzzy centralized decision analysis method,the production process and factors are sorted,and the suitable production process of plant-mixed hot recycled asphalt mixture is recommended.The results show that the optimum production process of plant hot recycled asphalt mixture with 20 % RAP content is as follows : mixing temperature is 165 °C.Firstly,RAP is mixed with new aggregates for 45 s,and then fresh asphalt is mixed for 45 s,and then mixed with preheated mineral powder for 90 s.Finally,the material is stored at 150 °C for 0.5 h.Finally,based on the large and mediumsized repair project of G206 in Yantai City,Shandong Province,the plant-mixed hot recycled asphalt mixture was applied in the physical engineering.Through the investigation of pavement diseases,the pavement regeneration scheme was proposed.Based on the target mix design results,the production mix ratio of hot recycled asphalt mixture is designed and verified.The quality control measures are put forward for the recovery,stacking,pretreatment and reclaiming of RAP in the construction process,and the mixing,paving and rolling of plant mixed hot recycled asphalt mixture.The pavement test results show that the recycled asphalt pavement is effective.Finally,based on the large and medium-sized repair project of G206 in Yantai City,Shandong Province,the plant-mixed hot recycled asphalt mixture was applied in the physical engineering.Through the investigation of pavement diseases,the pavement regeneration scheme was proposed.Based on the target mix design results,the production mix ratio of hot recycled asphalt mixture is designed and verified.The quality control measures are put forward for the recovery,stacking,pretreatment and reclaiming of RAP in the construction process,and the mixing,paving and rolling of plant mixed hot recycled asphalt mixture.The pavement test results show that the recycled asphalt pavement is effective.