Study On Aging Behavior And Recycling Technique Of Asphalt Pavement

Owing to superior performance and driving comfort, asphalt pavements account for a largeproportion in highways and city roads. However, after aging by the natural environment,physical and mechanical properties of asphalt mixture will become worse until it can not meetthe requirements of the traffic load. The recycling technology of Asphalt mixture is efficientpath to realize the asphalt pavement sustainable development. However, It is a new topic onthe recycling of asphalt mixture presently in china, the aging behaviour and the recyclingtechnology of asphalt pavement need to be systematical researchedFirst of all, aging characteristics of asphalt pavement in the natural environment areresearched and effect of time, pavement depth and volume of air voids on aging process ofasphalt pavement are given; Finite element method was adopted to analysize the mechanicalreaction, the larger of the facing modulus and modulus gradient, the deepper of the crack'sdepth. What's morer, the larger of the stress-intensity factor, that is to say, the worse of theroad pavement aging, the more of the road pavement structure's failure. The relevantconclusion have reference value to understand the aging and fatigue cracking of the asphaltpavement and consummate the designing method of the asphalt pavement.In order to probe into influences of exposure oxygen, heat, light and other factors affectingasphalt aging further, five kind of aging simulating tests containing three thermo-oxidativetests (RTFOT, PAV and oven aging at 60℃), thermal aging test without oxygen and UVaging were used in the research. Result of analysis shows that the thermo-oxidative aging isthe main form of pavement aging. The effect of RTFOT,PAV and oven aging at 60℃has agood relationship with each other, what's more, natural aging in the field has similar effectwith aging simulation tests in the laboratory, so the delay RTFOT can simulate asphaltlong-term aging well. On the basis of asphalt aging in the field and in the laboratory,evaluation methods of asphalt aging resistance based on viscosity and ductility of agedasphalt, which can provide a theoretical basis for pavement maintenance.The decay of asphalt properties caused by aging is in fact the external appearance of microstructural changes. Analysis of aging asphalt composition and infrared spectroscopy show thatthere are different composition change characteristics with different aging test method. Butthe mechanism of thermo-oxidative is common change with the two, which is the processionof chemical bond rupturing and oxygen increasing. Polar and hydrophilicity of asphalt is enhanced after aging, therefore water damage of asphalt pavement and asphalt aging promotemutually. Based on consideration of aging of asphalt and recycling mechanism, one kind ofnew style recycling agent was developed by taking used rubber as the raw material. The testresults indicated that this new style recycling agent show good result, the dosage of 10% wasproposed on the comprehensive consideration recycling effect and economy.How to estimate quality of old mixture, recycling of aggregate and asphalt was studied inthe paper, similarities and differences of hot asphalt recycled mixture and common asphaltmixture was compared, a good many factors that affect recycling effect was analysized andthe variety law of the performance of hot asphalt recycled mixture dependent on theproportion of old mixture and infection of the grade to the performance was studied. Based onthe conclusion of recycled mixture, the ascertain method of the worn-material mix rate, theascertain method of the aggregate, optimum asphalt content and the computing method of thenew mix asphalt dosage in the recycling asphalt mixture component composing was proposedin the paper.Based on the analysis and research of the entity project and the construction technics ofagitating, spreading and roller compaction during hot asphalt recycled mixture, the methodsof the old mixture recycling and disposing, the advice of increasing the temperature of the oldmixture were proposed in the paper. Finally, the economic benefits and social benefitsindicated that hot asphalt recycling technology can utilize plenty of old materials, which is notonly saving resource, but also protecting the environment, the extension of road hot asphaltrecycling technology can have better economic benefits and social benefits.