The Study On Aging And Regeneration Mechanism Of Asphalt With High Dosage Of Rubber

Asphalt with high dosage of rubber has the advantages of relatively low price,easy access to modifier and so on.It can aslo improve noise reduction performance of pavement and improve driving comfort.Furthermore,it can reduce environmental pollution caused by waste tires and improve resource utilization.At present,the modification mechanism,aging mechanism and regeneration mechanism of asphalt with high dosage of rubber are still unclear.In this paper,asphalt with high dosage of rubber was prepared and tested for aging and regeneration.The modification mechanism,aging mechanism and regeneration mechanism of asphalt with high dosage of rubber was revealed from three aspects:macroscopic performance test,microscopic test and molecular dynamics simulation.Rubber asphalt with 35%rubber powder content was prepared by an optimized process.The macro performance changes of it were evaluated by penetration degree,ductility,softening point test,rotational viscosity test and DSR test.Scanning electron microscope test,infrared absorption spectrum analysis and differential scanning calorimeter were used to observe the microscopic surface morphology,chemical composition change and temperature stability of it.The molecular dynamics model was established,and the changes of physical properties were evaluated from density,solubility parameters,glass transition temperature T_g,viscosity,modulus and diffusion coefficient.The results show that rubber powder is a good modifier for asphalt,and its compatibility is the best when the temperature is around 190℃.Compared with the matrix asphalt,the T_g of 35%rubber asphalt decreased by about 9℃,the viscosity increased by about 60%,the shear modulus increased by 76.4%and the elastic modulus increased by31.8%,showing better high and low temperature performance.The modification of asphalt with high dosage of rubber is mainly physical modification,and there is also chemical modification in which aromatic components participate in the reaction.The TFOT test and PAV test were used to simulate the short-term aging and long-term aging of asphalt with high dosage of rubber.The results show that After short-term aging and long-term aging,the rutting factor increased by 20.3%and 80.8%respectively,and the viscosity increased by 24.2%and 75.8%respectively.The short-term aging of asphalt with high dosage of rubber is“sticky and hard”,which is caused by the viscosity of asphalt caused by the volatilization of light oil content and the softening of rubber caused by the chain breaking of NR molecules.Long-term aging is characterized by“hardness and brittleness”,which is caused by asphalt hardening caused by light oil oxidation,rubber hardening and brittleness caused by SBR molecular chain cross-linking and agglomeration effect of rubber powder.The difference of solubility parameters between aged rubber powder and matrix asphalt becomes larger,the compatibility becomes worse,and the stability of the physical blending and mutual solubility system formed by rubber powder and asphalt becomes weaker,which makes it easy to cause segregation between materials.The regeneration test of asphalt with high dosage of rubber was carried out by using three methods:regeneration using rejuvenator,harmonic regeneration using matrix asphalt and rubber powder,and compound regeneration.The results show that for viscosity recovery,under short-term aging,the three regeneration methods can recover to 91.7%,94.7%and 98.8%.Under long-term aging,the three regeneration methods can recover to 80.1%,67.0%and 94.7%.Rejuvenator can restore the properties of matrix asphalt and styrene-butadiene rubber,and harmonic regeneration can restore the properties of short-term aged matrix asphalt and natural rubber.The regeneration process of short-term aging is mainly physical harmonic regeneration,accompanied by the transformation of some unstable sulphides into stable sulphides,which improves the temperature stability.During the regeneration process of long-term-aging samples,the hydroperoxide ROOH and macromolecule ROOR(asphaltene,gum)in the matrix asphalt were reduced to aromatic components,and the cross-linked product ROOR of the esterification reaction of SBR was reduced by chain breaking.The research results of this paper will provide reference for the production,construction,maintenance and regeneration of asphalt with high dosage of rubber.