Study On Fatigue Performance Of Recycled Aggregate Asphalt Mixture Of Concrete Construction Waste Under Temperature Humidity Coupling

In recent years,the output of construction waste in Beijing area keeps high.The asphalt mixture prepared by using Recycled Concrete Aggregate（RCA）and applied to the middle and lower layers of asphalt pavement is of great significance to the high-value and large-scale utilization of construction waste Recycled Aggregate.Aiming at RCA asphalt mixture under the effect of temperature-humidity coupling blank in the research of fatigue performance,and simulation in the Beijing area temperature-coupling equivalent fatigue test under wet condition,based on the characteristics of RCA,build suitable for RCA fatigue test method of asphalt mixture,the RCA asphalt mixture under the effect of temperature-wet coupling of fatigue properties change law and mechanism,It provides a theoretical basis for the high value application of RCA in asphalt pavement.Firstly,the basic properties of RCA from 4 different sources in Beijing area were analyzed,including appearance morphology,chemical composition,physical and mechanical properties,etc.,and the brick mix content of RCA was calculated based on color recognition method.The crushing value,Los Angeles abrasion loss,apparent relative density,gross volume relative density,water absorption,needle particle content and brick content were selected as RCA characteristics.Secondly,AC-20C RCA asphalt mixture was designed.Based on the physical and chemical characteristics of recycled aggregate and its crushing and thinning behavior during mixing and compaction,the initial grading of RCA asphalt mixture was modified by using the full mesh grading modification method and the synthetic density modification method.It is found that the coefficient of variation between the revised pass rate of each grade and the target gradation is less than 0.05%,and the variance is less than 0.1,so as to build the RCA asphalt mixture proportion design method.Thirdly,based on the data processing technology and probability statistics theory,the meteorological data of Beijing area in the past 20 years were mined and analyzed,and the equivalent fatigue test under the temperature-humidity action in Beijing area were simulated,that is,the maximum number of annual freezing-thawing alternating action was 65 times,the interval of freezing-thawing alternating temperature was-8～10℃,and the average relative humidity was 47%.,and in combination with indirect tensile fatigue test,the fatigue test method of asphalt mixture under temperature-humidity coupling action was established.Finally,the change rule and action mechanism of fatigue performance of 4 kinds of RCA asphalt mixtures and natural Limestone aggregate（LSA）asphalt mixtures under the action of temperature-humidity coupling were studied.It was found that the initial fatigue performance of mixtures was in the order of LSA>RCA₁>RCA₂>RCA₃>RCA₄.The fatigue damage of asphalt mixture is in the stage of rapid accumulation when the number of temperature-humidity coupling action is 150 times（equivalent to 2 years）.After 150 times（equivalent to 2 years）,the fatigue performance of asphalt mixture tends to be stable.After 650 times（equivalent to 10years）,the fatigue life of asphalt mixture is in the order of RCA₁>RCA₂>LSA>RCA₃>RCA₄.In addition,through the analysis of fatigue characteristic parameters of the constructed fatigue equation,it is found that the higher the gross volume relative density and apparent relative density of the aggregate,the better the initial fatigue resistance.The larger the brick content of aggregate is,the slower the decay rate of its fatigue property is under the temperature-humidity coupling action.Through the research of this project,the decay law and action mechanism of fatigue performance of RCA asphalt mixture under the action of temperature-humidity coupling are clarified,which fills the research blank in this field and provides solid theoretical support for the application of RCA in asphalt pavement.