Study On Rheological Properties And Microstructure Of Warm Mix Asphalt Under Ultraviolet Aging Condition

Warm mix asphalt(WMA)pavement technology is a kind of energy-saving pavement technology,which can reduce energy consumption,smoke emission and environmental pollution.The average temperature is low,the ecology is fragile,and the construction season is short in Northwest China.Therefore,the WMA pavement technology is more suitable for paving in the northwest region.However,ultraviolet radiation is strong in Northwest China.A large number of studies have shown that UV aging can seriously reduce the service life of asphalt mixtures.However,there are few studies on the anti-UV aging performance of warm asphalt pavement at home and abroad.In addition,because of its low mixing and construction temperature,the adhesion of WMA was effected,which makes the asphalt mixture have some potential of the water damage.However,few literatures have studied the adhesion characteristics and mechanism of WMA under ultraviolet aging conditions.The adhesion characteristics and adhesion mechanism of WMA were studied.To this end,this study studied the rheology and adhesion properties of WMA under UV aging conditions,and based on atomic force microscope(AFM)and other microscopic testing methods,the UV aging mechanism was analyzed.In this paper,dynamic shear rheometer is used to study the rheological properties of asphalt samples under different temperature and loading frequencies.The influence of ultraviolet aging on the rheological properties of asphalt was analyzed with the complex shear modulus and phase Angle as index parameters.Secondly,the AFM force spectrum scanning test was carried out to obtain the nano adhesion force of WMA under ultraviolet conditions,and the nano adhesion performance of WMA was characterized from the perspective of nano adhesion.In combination with GPC test,the change of molecular content of temperature-mixed asphalt during ultraviolet aging was analyzed,and the correlation analysis of nano adhesion force and large molecular weight data was carried out,so as to study the microcosmic mechanism of the influence of ultraviolet conditions on the adhesion characteristics of temperature-mixed asphalt.Finally,the microstructure of WMA after ultraviolet aging was studied,and the microstructure of WMA was measured by AFM to explore the microcosmic mechanism of the influence of ultraviolet aging on the rheology and adhesion characteristics of WMA.The surface area ratio and roughness of bee-like structure of asphalt micro-surface were used to quantitatively characterize the changes of micro-structure of temperature-mixed asphalt during ultraviolet aging,so as to compare and analyze the effects of ultraviolet aging on adhesion of temperature-mixed asphalt.On this basis,AFM can also obtain the three-dimensional topography of WMA,and analyze the effect of ultraviolet aging on the microstructure of WMA from a three-dimensional perspective.The conclusions of this study are as follows:(1)The incorporation of Evotherm and Sasobit reduces the total resistance of SK asphalt when subjected to repeated shear deformation.Among the two kinds of WMA,Evotherm warm mix asphalt is less affected by repeated shear deformation.Under the condition of aerobic and photo-oxidation coupling,there is a certain difference in the effect of ultraviolet aging on the rheological properties of WMA.(2)The nano adhesion of SK matrix can be improved by adding Evotherm warm mix,but the nano adhesion of SK matrix can be decreased by adding Sasobit warm mix.UV aging in different aging methods has the greatest influence on the adhesion properties and macromolecular content of SK mixed asphalt.In the process of UV aging,the film formed on the surface of temperature-mixed asphalt hinders the aging process and also slows down the nano adhesion property of temperature-mixed asphalt.(3)From the perspective of the phase diagram,the rheological properties of WMA can be characterized to some extent.After the UV aging of WMA,its microstructure fluctuation amplitude increases,peak structure cluster decreases greatly,and more valley area is produced,which leads to the decrease of bee structure and the increase of roughness.The effect of the surface topography of WMA is more serious.After UV aging,a large amount of warm mixed asphalt valleys appeared,and microscopic cracks on the surface were forming.