| In the near future,the focus of highway network layout in China will be shifted to the west and low-latitudes reigons with intense ultraviolet radiation.Asphalt pavement has been widely used for its excellent road performance.However,asphalt tends is likely to age under the solar ultraviolet radiation,resulting in asphalt pavement diseases.Therefore,conducting the research on the anti-ultraviolet photo aging performance of asphalt is of great importance to improve the durability of asphalt pavement.In this paper,five light stabilizers namely which are benzotriazole UV absorbents UV928 and UV234,hindered amine light stabilizers LS111 and UV4050,and ultraviolet light screening agent LDHs were selected for preparing modified asphalts to perform accelerated UV-aging simulation laboratory tests by a self-made ultraviolet environment box after the TFOT aging.The rheological properties before and after UV aging of five kinds of light stabilizer modified asphalts with different dosages were compared and analyzed.The results indicated that the addition of light stabilizer in asphalt showed increase result in viscosity and complex modulus of asphalts while decrease in phase angle after UV aging,resulting in poor rheological properties.Based on the creep rate aging index and stiffness modulus aging index and combined with the changes of complex modulus aging index,viscosity aging index and the changes of phase angle before and after UV aging,three light stabilizers namely UV928 UV4050 and LDHs were selected with the optimum dosages of 0.5%,0.5%and 3%respectively.Furthermore,based on the action mechanism of the three kinds of light stabilizers,the three light stabilizers selected were compounded to give full play to the synergistic interaction.The rheological properties of nine kinds of composite light stabilizer modified asphalts were measured through different kinds of tests namely Brookfield viscosity,bending creep,DSR temperature scanning and DSR mid-temperature fatigue tests.The results showed that compared with the virgin asphalt,the viscosity values of the composite modified asphalts increase while the stiffness modulus,rutting factor and viscosity increment decrease before and after UV aging.The optimal group allocation ratio was UV928:UV4050:LDHs=0.5:0.7:4 using the regression evaluation method combined with the above five indexes.Finally,the comprehensive evaluation of the anti-aging performance of the optimal composite light stablizer modified asphalt was carried out.The properties and functional groups changes were measured under different UV illumination time based on rheology,FTIR test and Cantabro test.And the UV aging resistance was verified from the perspective of property and microstructure.It was found that the optimal composite light stabilizer modified asphalt has more excellent anti-ultraviolet aging propertythan the virgin asphalt. |
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