Study On Dynamic Mechanical Properties Of SBS Modified Asphalt Mortar Under Ultraviolet Radiation

The solar ultraviolet radiation can result in the aging of asphalt pavement materials,gradual hardening,fracturing,and increased low temperature stiffness of asphalt.The damage strain of stress fatigue of temperature is reduced.The adhesion between asphalt and aggregate decreases after ultraviolet aging.Some asphalts and aggregates separate and fall off,which causes low temperature cracking,fatigue cracking and pits of asphalt pavement,and seriously affects the road performance and durability of asphalt pavement.In order to further study the dynamic mechanical properties of ultraviolet aging asphalt mixture from the meso-level,based on mix proportion of AC-13 Styrene Butadiene Styrene(SBS)polymer modified asphalt mixture,the coarse aggregate was removed.The remaining fine aggregate was scaled up,and the mix proportion of asphalt mortar was calculated.The asphalt mortar specimens were prepared by self-developed dynamic mechanical analysis(DMA)asphalt mortar mould.The aging test of SBS modified asphalt mortar under different working conditions was carried out by the self-developed ultraviolet environment simulation box.Based on the dynamic viscoelastic theory of materials,the DMA was used to analyze the dynamic mechanical property.The stress-strain relationship and dynamic modulus variation characteristics of asphalt mortar before and after ultraviolet aging were evaluated by dynamic mechanical analyzer for stress-strain scanning test,temperature scanning test and different frequency-temperature scanning tests of asphalt mortar before and after ultraviolet aging under different working conditions.The SEM test was carried out to analyze the surface microstructure changes and damage characteristics of asphalt mortar under different working conditions before and after ultraviolet aging.Results of stress-strain scanning test showed that with the increase of ultraviolet radiation time,the slope of linear function increased gradually,but the slope of stress-strain relationship function at low intensity and short radiation time was similar to that of original asphalt mortar,and some experimental results coincided.At the same irradiation time,the slope of stress-strain linear function increased as the ultraviolet intensity increased.Results of temperature scanning and different frequency-temperature scanning tests showed that the change rules of storage modulus and complex modulus were the most obvious under high frequency and long radiation.With the extension of ultraviolet radiation time/intensity of asphalt mortar specimens,the storage modulus and complex modulus increased gradually.In the middle and high temperature range,the viscous modulus changed regularly after ultraviolet aging.With the extension of ultraviolet radiation time/intensity of asphalt mortar specimens,the loss modulus increased gradually.The loss factor increased first and then decreased with the increase of temperature.The peak value was the original asphalt mortar.The loss factor fluctuated greatly in other radiation time periods,and there was no obvious regularity.Results of SEM test showed that with the prolongation of ultraviolet radiation time,the asphalt mortar cracked or damaged from the surface down.The ultraviolet radiation intensity accelerated the aging of asphalt mortar and shortened the decay time of asphalt mortar.