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Study On Aging Mechanism And Rheologic Behavior Of Asphalt Under Simulate Ultraviolet Environment

Posted on:2009-03-06Degree:DoctorType:Dissertation
Country:ChinaCandidate:J N WangFull Text:PDF
GTID:1102360278962006Subject:Road and Railway Engineering
Abstract/Summary:PDF Full Text Request
The area, about 33% of the total land area of China,is at altitude of 2000m above, in which, the UV radiation intensity is almost 4-5 times of plain areas.Severely ultraviolet aged asphalt is one of the most important reasons for early damage of asphalt pavement. In this paper, indoor accelerated simulation of outdoor ultraviolet aging of asphalt is carried out by improving original aging equipment; road performance of ultraviolet aged asphalt is studied based on rheology; ultraviolet aging mechanism is analyzed by means of infrared spectrum and thin-layer chromatography; in comparison of performance of multiple improvement measures, suggestions on anti-ultraviolet aging is proposed. All research works in the paper are outlined as following:In order to simulate veritably the outdoor ultraviolet aging, the original uv aging equipment is improved, selecting more reasonable ultraviolet radiation lamp and adding cooling and gas supply systems; in addition, the calculation method of indoor ultraviolet aging velocity gradient and the method of indoor accelerated ultraviolet aging are determined.The rheological properties of ultraviolet aged asphalt and its interaction capability with aggregate powder have been comprehensively analyzed based on dynamic rheology. Studies have shown that the complex modulus of ultraviolet aged asphalt increases, phase angle decreases and the low temperature deformability has deteriorated, so it is more susceptible to brittle cracking; what's else, increase of rutting factor indicates that high temperature performance of ultraviolet aged asphalt has been improved in different degrees; Studies on interaction between asphalt and powder show that the interaction capability declines catholically after ultraviolet aging, no influence of asphalt type, lithology and powder size.Material properties and mechanical behaviors of asphalt have been altered by ultraviolet aging.Asphalt becomes more rigid and brittle after 220h ultraviolet aging; with aging time prolonged, on one hand, viscosity-elasticity transformation frequency declines and it indicates that the transition temperature increases at which ultraviolet aged asphalt is transformed from viscosity region to elastic region and therefore asphalt is more sensitive to low temperature cracking. On the other hand, the decrease of phase angle implies proportion of viscosity and elastic composition has been altered and the viscosity composition declines, consequently ,it is hard for asphalt to relax stress resulting from temperature and load and then low temperature cracks appears. Moreover, with aging time prolonged, glass transfer temperature increases, and it indicates that the relaxation time of molecular chain segment in glass state is far more than force action time, and this explains why ultraviolet aged asphalt is susceptible to brittle failure at low temperature.Ultraviolet aging is oxidation reaction in which aromatic and resin are main materials and saturated fragrance promotes the ultraviolet oxidation reaction of aromatic and resin. After ultraviolet aging, saturated fragrance produces small amount of resin and asphaltene, aromatic transforms into resin and asphaltene and resin and asphaltene transform into asphaltene.Studies on effect of ultraviolet aging on colloidal structure stability have shown that a strong combination, which is presented as aggregation and precipitation of asphaltene in macroscopic view, is produced between resin and asphaltene. In course of ultraviolet aging,asphalt changes from sol to gel,from colloid to solid. In IR spectra comparison of ultraviolet aged and unaged asphalt, ultraviolet aging characteristic peak is found and it is pointed out that the performance of different asphalts tends to be uniform after a period of aging. Researches on consistency and reaction degree of group composition show that saturated fragrance has a strong effect on ultraviolet aging performance of asphalt. Asphalt with a higher content of saturated fragrance ages more strongly and the rheology deterioration is more obvious.Through road performance comparison and verification of various schemes, it is found that modified asphalt behaves a stronger anti-ultraviolet aging ability than base asphalt; anti-ultraviolet aging effect of SBR is better than SBS;ultraviolet absorbent,antioxidant and light stabilizer all posses anti-ultraviolet aging ability; tests have proved joint use of light stabilizer and SBR show better anti-ultraviolet aging ability than combination of other anti-aging agent and modifier.
Keywords/Search Tags:Asphalt, Ultraviolet Aging, Mechanism of Ultraviolet Aging, Viscosity-elasticity transformation frequency, Disabled temperature
PDF Full Text Request
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