Study On Aging Mechanism And Characteristics Of SBS Modified Asphalt Based On Ultraviolet Radiation

Solar ultraviolet radiation will lead to the aging of asphalt pavement,degrade the road performance and reduce the service life.As the construction of China's road network is gradually shifting to the western regions with high altitude and low latitude areas with intense ultraviolet radiation,and the ozone layer become thinner caused by the deterioration of the global climate,the aging problem of asphalt pavement is increasingly evident.In this paper,the commonly used SBS modified asphalt is selected to the study the mechanism of ultraviolet aging and the characteristic of performance decay.It is of great significance to the improvement of the durability of asphalt pavement,and provide theoretical basis and reference value for anti-UV and preventive maintenance of asphalt pavement.The 2 x 4 x 4 simulated aging orthogonal experiments under different working conditions(wavelength,intensity,time)and the solar exposure aging tests were carried out for comparative analysis by using the UV environment simulation box developed by our research group.Based on the characteristics of performance decay,apparent morphology and microstructure changes,the radiation intensity and time have the cumulative effect of aging,but do not follow the principle of equivalent total radiation.The shorter the ultraviolet wavelength is,the greater the energy is,and the stronger aging effect on asphalt is.The decay characteristics of ultraviolet aging properties of SBS modified asphalt were studied by means of three index tests and rheological methods.Compared with TFOT aging,SBS modified asphalt after ultraviolet aging generally shows as follows:(1)The penetration decreases.The residual penetration ratio after 80 days of solar aging was only 33.9%;(2)The softening point fluctuated slightly;(3)The ductility decreased,even can not be measured;(4)The viscosity increased.The increase of viscosity under indoor ultraviolet aging was relatively small,especially 395 nm ultraviolet aging and the maximum viscosity aging index was only 0.287,while the viscous aging index of solar ageing can reach 1.512;(5)The rutting factor increases,especially the solar aging,and the aging factor of the rutting factor was up to 2.79,indicating that the high temperature stability was improved,but the creep stiffness at low temperature bending modulus increased generally,indicating that the decrease of crack resistance at low temperature.(6)SEM test and fluorescence microscopy were used to characterize the apparent morphology of SBS modified asphalt after ultraviolet aging and the morphology and distribution characteristics of SBS in asphalt base.UV aging will lead to the degradation of SBS,and SBS becomes scarce and ambiguous in the asphalt base.The SBS modified asphalt becomes hard and brittle,which causes surface cracking;(7)The microstructure and aging mechanism of SBS modified asphalt after UV aging were studied by FTIR test.The results show that the absorption peaks of carbonyl and sulfoxide groups become larger after UV aging,while the absorption peaks of C=C and PS segments of PB in SBS are opposite,indicating that the asphalt base undergoes oxygen absorption reaction during aging,and SBS degrades.The molecular structure changes and recombination degraded its performance.