Study On Application Of Hot Mix Recycled Asphalt Mixture In Flexible Base Course

Highway industry in our country has entered into new area of construction and building,and a lot of waste asphalt mixtures will be produced in the process of maintenance and repair.More than 1.6 tons of waste asphalt mixture will be produced every year.If not handled properly,it will not only cause a lot of wastes,but also serious environmental pollution problems.In addition,The costs of petroleum and stones are rising because of their decline in their production,consequently the cost of road construction keeps rising.So it is an urgent problem to solve the problem of an efficient utilization of the recycled asphalt mixtures.Based on the application of recycled asphalt mixture in flexible base,three recycled asphalt mixtures of 30%,40% and 50% are designed.According to the proportion of in each RAP content,blends of aged and virgin asphalt binders were prepared.By using atomic force microscope(AFM),Fourier transform infrared spectrometer(FTIR),infrared spectrometer,dynamic shear rheometer(DSR)and bend beam rheometer(BBR)of the Recycled asphalt mixture(RAP),the effects of bleeding and diffusion of the virgin and aged asphalts were studied by different test methods.The results showed that: with the increase of aged asphalt's content,the number of “bee-structure” in blends is getting less,the average area is getting larger,and the maximum area remains approximately the same.The carbonyl index and sulfoxide indexes of blend showed the same rule in change with the increase of the aged binder.When the content of aged asphalt binder is more than49.3%,all AFM factors and functional group indexes change greatly.Linear regression analysis showed that the carbonyl index and sulfoxide group index of regenerated asphalt had a good correlation with its rutting factor.At the same time,the root mean square and modulus root mean square and modulus of recycled asphalt have a good correlation with its stiffness modulus.At the same time,the pavement performance of asphalt mixture with different dosage is tested respectively.The results showed that the high temperature stability of hot recycled mixtures increases and the low temperature performance and water susceptibility decrease with the increase of RAP content.When the content of RAP is more than 40%,the crack resistance and water stability of hot mix asphalt decrease greatly.When the content of RAP is 50%,the low temperature bending tensile strain of hot recycled asphalt mixtures could not meet the specification requirements.The influence of pre-heating temperature for RAP and mixing sequence of aged asphalt mixtures on the volumetric properties and the performance of recycled asphaltmixtures.The results showed that when the heating temperature is lower than 110 Celsius degrees,the volume index of recycled asphalt mixture changes greatly.The water stability and low temperature cracking resistance of recycled asphalt mixture were greatly affected.