Design Of Cold Recycled Asphalt Pavement Strucure In Tanshao Expressway Rehabilitation

At present,the asphalt pavement built in the 1990 s is seriously damaged or has reached the end of its service life,so most of the work in the future is to repair the damaged pavement.The maintenance of the damaged road will produce a large amount of old asphalt mixture.If the old asphalt mixture is discarded,it will pollute the surrounding environment and occupy the land.Cool recycled technology is widely popularized and applied in the maintenance and reconstruction of asphalt pavement due to its advantages in environmental protection,saving resource,saving total investment,improving the working condition and shortening the time of construction.The research on cold recycled technology in China started late,experts mostly specializing in the cold recycled mixture,such as regenerative binder,mix ratio and using performance,etc.Therefore,it is necessary to specially study the structure design of the cold recycled asphalt pavement to provide reference for the promotion and application of cold recycled technology.This thesis is based on the overhaul project of Xiangtan~Shaoyang freeway in Hunan,including the evaluation of old road condition by field test,and the analysis of the old road damage form and causes.Old materials from onsite milling were used with emulsified asphalt to design cold recycled mixture,and the performance of the mixture was tested.The test results show that technical indicators of cold recycled mixture with emulsified asphalt meet the requirements of lower layer and base.For the sake of insurance,cold recycled mixture with emulsified asphalt is used as the base layer in pavement structure.The mechanical performance of cold recycled pavement with emulsified asphalt was calculated through finite element method and curing time tests of cold recycled mixture with emulsified asphalt,and the cumulative equivalent axle loads and the ultimate axle load of the pavement structure are analysed.The analysis shows that old pavement conditions have a significant influence on the cumulative equivalent axle loads and the ultimate axle load of the pavement structure;the cumulative equivalent axle loads significantly increase with the increase of curing time of cold recycled mixture with emulsified asphalt,while the ultimate axle load decreased;Increasing the thickness of the recycling layer can improve the cumulative equivalent axle loadsand the ultimate axle load of the pavement structure.In project,suitable cold recycled pavement structure with emulsified asphalt should be adopted according to the actual situation,and then determine the thickness of the cold recycled layer.According to the performance of cold recycled mixture,three typical cold recycled asphalt pavement structure are recommended.Based on JTG D50-2006 specification and domestic alspht pavement design ideas,the structure design method of cold recycled asphalt pavement is constructed and the thickness design of three typical schemes is obtained for different traffic and strength grade of old road.Based on JTG D50-2017 specification and existing research results at home and abroad,the structure design of cold recycled asphalt pavement is constructed by using the dynamic modulus of pavement materials and more reasonable design indexes.then the thickness design of three typical schemes is obtained by the design method.