Investigation On Bitumen Aging And Mechanism Of Rejuvenating Based On Components Modification

With the service,time goes by the combination of construction and conservation takes the place of simply construction.The large-scale maintenance of asphalt pavement is coming in our country.Recycling and reclaiming asphalt concrete saved non-renewable resources like bituminous material in an utmost extent.Economic cost saves as well.Ageing,which is the inverse process of rejuvenation,was researched with profound meaning.In this research,ageing was divided into two parts,namely physical ageing and chemical ageing.GC-MS(Gas Chromatography Mass Spectrum)was engaged to simulate the volatilization of organic compounds from bitumen at130 ? and 180 ?.In this way,the mechanism of physical ageing process of base bitumen was researched.TFOT,PAV,UV,acid solution steeping were used to simulate the heating process,high-temperature and high-pressure service process,illumination ageing process and acid rain erosion process,respectively.Four components and FTIR(Fourier Transform Infrared Spectroscopy)test were engaged to research the mechanism of bitumen ageing.FTIR was used to analyze the functional group of rejuvenator after thermal dehydration.In order to match the effect with the functional group,small organic molecules with same functional group were added into traditional rejuvenator respectively to make up a series of new rejuvenators with specific functional groups.To modify with single functional group,2wt% absolute ethyl alcohol,ethylene diamine,acetone and acetaldehyde were added into rejuvenator,respectively.Needle penetration,softening point and viscosity from ageing bitumen with varying degrees was tested.The result showed that the properties of ageing bitumen changed to base bitumen.However,different rejuvenator with different small molecules had different impact on rejuvenation effects.The result showed that the rejuvenator improved the properties of ageing bitumen.However,rejuvenator with different chemical reagent had different rejuvenation effects.PAV ageing bitumen had a larger carbonyl index than TFOT ageing bitumen.Therefore,carbonyl did not fit for PAV rejuvenation in the aspect of softening point.Aldehyde group and carbonyl group were helpful to TFOT and UVageing bitumen.In the aspect of needle penetration,hydroxyl and amidogen are helpful to PAV ageing bitumen,while carbonyl group and aldehyde group contribute to the rejuvenation properties of TFOT and UV ageing bitumen.In the aspect of viscosity,aromatic components were helpful to the viscosity of bitumen instead of chemical reagent.DSR(Dynamic Shear Rheometer)was engaged to test rheology properties of all bitumen.The result showed that all the complex modulus increased,while phase angle decreased after ageing,and the variation of complex modulus and phase angle is proportional to the ageing degree.The rejuvenator improved the rheology properties of all kinds of ageing bitumen.However,differences existed between reclaimed bitumen rejuvenated by different rejuvenators with different chemical reagents.Aldehyde group play a positive role to the properties of TFOT ageing bitumen,while hydroxyl and amidogen play a negative role.To PAV ageing bitumen,hydroxyl and amidogen are helpful to rejuvenation.As for UV ageing bitumen,aldehyde group and carbonyl group are positive additive.A conclusion can be drawn that the effect of rejuvenator depend on the ingredient of ageing bitumen.Therefore,under the circumstance of thermal regeneration and maintenance on bituminous pavement,the extent and degree of ageing should be seriously taken into consideration.Then,excellent rejuvenating material was chosen with pointed references.