Research On Depth And Properties Of Ultraviolet Aging Of Asphalt And Its Mixture

For the past few years,the mileage of asphalt pavement is increasing rapidly in our country's highway construction.Asphalt has been widely used as a kind of road material around the world due to its excellent properties.But the asphalt is suffering from all kinds of extraneous factors and vulnerable to ageing damage in service like other polymers over the years.As a consequence of ageing,the performance properties deteriorate,service life shortens and the maintenance funds raise largely.While the damage of ultraviolet radiation is more prominent to bitumen and UV-ageing is one of the most common ageing manners of asphalt.In this paper,a new method that using the carbon disulfide solution to dissolve and peel off the UV-aged base asphalt layer upon layer was used to discuss the properties and process of UV ageing.What's more,the effects of ultraviolet radiation to the properties of different void asphalt mixtures were researched.First of all,the temperature sweep test and frequency sweep test were commanded by using dynamic shear rheometer to discuss the change regulation of rheological properties of different UV-ageing depth specimens.The results indicated that UVageing depth increased with UV-ageing time.A liner relationship between complex modulus ratio of top layer specimen and UV-ageing time was founded.When the ageing time was fixed,asphalt aged from the surface to the center,its complex modulus had a power function relation with ageing depth.The results of temperature sweep test and frequency sweep test both showed that complex modulus decreased and phase angle increased from the surface to the center,meaning that the rheological properties of UV-aged asphalt deteriorated.Secondly,the dissolved stripped UV-aged specimens were investigated by four components analysis and infrared spectrum analysis.The results of four components showed that components of different UV-ageing time specimens had a same change regulation that its aromatic content reduced,resins and asphaltenes raised,saturates swung lightly.The top layer specimens' components transformed seriously as the UVageing time lasted.The colloidal structure of asphalt binders changed after UV ageing.These two asphalt binders' colloidal index had the same decreasing trend as the UVageing depth deepened.And the results of FTIR implied that the carbonyl index went up greatly,the sulfoxide index increased slightly as the UV-ageing time lasted.When UV-ageing time fixed,the carbonyl index declined sharply first and fell slowly then,the sulfoxide index descended laxly always as UV-ageing depth deepened.Finally,two different types(AC-13 which void volume is 4.5% and OGFC-16 which void volume is 20%)of asphalt mixtures were designed to investigate the effects of ultraviolet radiation to the properties of different void asphalt mixtures.The mixture specimens of UV-aged for some days were experimented by splitting test and fatigue test.The results evinced that splitting strength of AC-13 mixtures almost unchanged and splitting strength of OGFC-16 mixtures increased.The AC-13 specimens of UVaged for different days had the same fatigue property and the OGFC-16 specimens' deteriorated as the UV-ageing days lasted.