Study On Road Performance And Pavement Structure Of Foamed Asphalt Cold Recycled Mixture

At this stage,China’s high-grade highway construction mainly enters the stage of renovation and expansion and large-scale repair.In this process,a large amount of old asphalt pavement is produced.How to recycle the pavement old materials efficiently and greenly is the main research hotspot at present and in the future.The foamed asphalt cold recycling technology has the advantages of relatively high performance,low cost,energy saving and environmental protection,and has broad application prospects.However,the research on the performance of foamed asphalt cold recycled mixture and the pavement structure is still unclear.This paper studies this in order to provide reference and reference for similar engineering construction.The foaming mechanism and foaming characteristics of foamed asphalt were studied.The foaming mechanism of foamed asphalt was mainly combed and the influence of asphalt type,experimental temperature and water consumption on foaming effect was studied based on its mechanism.It is determined that Zhonghai 70# has the best effect and the optimum foaming conditions for foamed asphalt are determined as follows: the optimum temperature is 170 °C,and the optimum water consumption is 2.5%.According to the research on the properties of RAP materials and comparing the gradation after RAP material extraction,the study found that the old asphalt in the recycled materials is more aging,the attenuation of the three major indicators are more than 50%,and the actual set after extraction.The fines content in the feed increased significantly.Then,according to the design of the experimental grading,according to the standard mixture mix design process for indoor experiments,the optimal water consumption and asphalt dosage were 5% and 3.5%,respectively,and the mixing ratio was verified by laboratory tests.The water stability,low temperature crack resistance and mechanical properties of cold reclaimed mixture were studied.The effects of cement and foamed asphalt on its properties were studied.The research shows that cement can improve the water stability and compressive strength of the mixture.And the modulus of resilience,but the increase of its content will reduce the low temperature crack resistance of the mixture;the effect of foamed asphalt on the water stability,compressive strength and rebound modulus of the mixture has the best dosage value,and the mixture has low temperature resistance.The cracking performance gradually increases with the increase of the amount of foamed asphalt.Therefore,the design of the mixture should take into account its water stability and low temperature crack resistance.Finally,based on the detailed investigation of the structure and materials of cold reclaimed pavement in the country,the finite element model was established by means of ABAQUS finite element software.The effects of the application level of the cold recycled mixture,the thickness of the structural layer,the elastic modulus of the recycled material and the load on the tensile and tensile strains of the surface layer and the base layer were analyzed.