Study On Ultraviolet Aging Behavior And Anti-aging Of Asphalt In Tibetan Area

Cracking and looseness of asphalt pavement are affected by environmental factors such as light,oxygen and heat during service.The ultraviolet ray in the solar radiation is the main factor leading to the decay of asphalt performance,especially in the areas with high radiation intensity.As a representative of typical strong ultraviolet radiation areas,Tibet has a deterioration in the performance of road asphalt due to ultraviolet aging behavior,which affects the driving safety and service life.In addition,the establishment of asphalt ultraviolet aging characterization system is still lacking.This thesis relies on the asphalt pavement pre-prevention and maintenance project of ordinary national and provincial roads in Shannan,Tibet,90 # base asphalt and SBS modified asphalt commonly used in maintenance and construction in Shannan region of Tibet in recent two years were selected for outdoor engineering aging test and indoor accelerated ultraviolet aging simulation test.Based on the outdoor test,verify the credibility of the indoor simulation test,explore the development law of the macro performance(physical index,rheological index)and micro characteristics(structural morphology,chemical change,component transformation)in the process of road asphalt aging by solar ultraviolet radiation and indoor mercury lamp ultraviolet accelerated aging,build the relationship equation of indoor and outdoor ultraviolet aging,and improve the UV aging characterization system,It provides theoretical support for reasonable evaluation of asphalt UV aging behavior and research on anti-aging enhancement technology.(1)Based on the conversion of equivalent ultraviolet radiation,the annual average ultraviolet radiation in Shannan region of Tibet and the annual average ultraviolet radiation in the main urban area of Chongqing are converted into the indoor ultraviolet aging chamber accelerated simulation test radiation.Theoretically,it is estimated that the indoor accelerated aging days are 17.8 days and 7.3 days respectively under the annual cycle of outdoor ultraviolet light in the representative areas of high radiation in the south of Tibet and low radiation in the main city of Chongqing.(2)Before and after the outdoor aging test of road asphalt,the macro and micro indexes of asphalt under the action of high and low radiation intensity are significantly different.The decay degree of asphalt aging index in Tibet and Chongqing has a linear relationship with the annual average radiation multiple.The greater the radiation intensity,the lower the gloss and smoothness of asphalt surface,the more severe the decline of sample hardness and brittleness.The radiation intensity is the main factor affecting the decay of asphalt macro and micro properties.(3)The indoor accelerated ultraviolet aging test asphalt sample index change trend is consistent with the outdoor actual aging.The component change relationship is that the light component(saturated component and aromatic component)transforms to the heavy component(asphaltene and resin),the overall structure tends to gel stable state,the carbonyl and sulfoxide functional group concentration increases,and the continuous phase proportion increases,and the roughness decreases.The structure,morphology,chemical reaction and component conversion have a good correlation.The aging degree is deepened,the polar functional groups are increased,and the typical representative asphaltene is agglomerated and associated.A variety of oxidative polymerization reactions cause molecular structure changes,thus changing the high and low temperature properties of asphalt.(4)Based on the grey correlation theory and Arrhenius equation,the correlation between macro and micro parameters and the indoor and outdoor ultraviolet aging prediction equation are established,and the reduction coefficient is proposed for the equivalent radiation conversion.The reliability of the aging kinetic equation established by the macro indicators is higher than that of the micro parameters,and the ultraviolet aging behavior can be evaluated by the decay equation of the ductility and penetration indicators.(5)Based on the project cost,the introduction of ultraviolet absorbent can effectively improve the ultraviolet resistance of road asphalt.The amount of ultraviolet absorbent uv-531(1%)has a better effect on improving the low-temperature performance of the base asphalt.The combination of metal oxide material composite absorbent can effectively solve the technical problems of asphalt aging in high radiation intensity areas such as Tibet.