Study On The Influence Of RAP Variability On Road Performance Of Foamed Asphalt Mixture

Under the overall trend of "from construction to maintenance",the scale of maintenance is growing day by day.Although the recycling technology of asphalt pavement can reuse the old asphalt mixture produced in the maintenance process,the low utilization rate of the old asphalt mixture can no longer meet the demand of pavement maintenance at present.Cold recycling technology of foamed asphalt can improve the utilization rate of old materials and protect the ecological environment on the premise of ensuring the road performance of mixture,which is in perfect agreement with the green development concept in China.At the beginning of the 21 st century,scholars in China have carried out a series of researches on foam asphalt raw materials,strength,durability,shear resistance and dynamic modulus of foam asphalt cold recycled mixture,and paved test sections.However,there is little research on the variability of old asphalt mixture and its influence on the variability of foamed asphalt mixture,and the research on the variability of old materials mainly focuses on the field of thermal regeneration.Taking RAP variability as an object,this paper analyzes the causes of RAP variability and its influence on road performance of foamed asphalt mixture,and controls the variability of old asphalt mixture through construction technology and mix design,so as to obtain stable foamed asphalt mixture and improve its performance.It is found that RAP variability is different with different milling speeds,different lanes and different horizons.In this paper,the weight of influencing RAP variability is obtained by orthogonal test: milling speed > horizon > pavement diseases > different lanes,and the optimal milling speed is determined as 6-8m/min.Based on RAP variability,this paper studies the influence of RAP variability on the road performance of foamed asphalt mixture.It is found that asphalt content and RAP gradation variation have the greatest influence on the mixture performance,while old asphalt properties have little influence on the mixture performance.By comparing the RAP gradation with the extracted gradation,it is found that there is a big gap between the passing rates of the two gradations,and it is more reasonable to use RAP gradation for mixture ratio design.Based on this,the RAP is crushed and screened,and the RAP content control method is adopted to design the mixture ratio.The practical engineering application in western Chongqing proves that the variability of the mixture has been effectively controlled.Based on BP neural network,the performance of foamed asphalt mixture after RAP variability treatment is pre-estimated,and the experimental data is analyzed in a more accurate and efficient way to improve the scientific nature of the test.