Study On Micro Mechanism Of Regeneration And Adhesion Characteristics Of Aged Asphalt In Northwest China With Strong Ultraviolet Radiation

In recent years,adding waste asphalt mixture（RAP）in the process of pavement construction has become the mainstream trend of research,in which the regeneration of aging asphalt in RAP is the most important.Due to the strong ultraviolet radiation in Northwest China,asphalt not only suffered thermal oxidative aging,but also suffered serious photooxidative aging.Therefore,the research and development of asphalt recycling agent in Northwest China should not only consider the influence of thermal oxygen aging,but also take into account the influence of ultraviolet aging.In addition,there are two problems in the process of asphalt recycling:one is the diffusion and fusion of recycled agent and aged asphalt;the other is the adhesion between recycled asphalt and aggregate.These two problems are closely related to the durability of recycled asphalt mixture and the pavement performance after regeneration.Based on this,this paper developed a recycling agent for the northwest strong ultraviolet region aging asphalt,and studied the performance of recycled asphalt.In addition,the diffusion and fusion law of regenerant in aged asphalt were studied from three aspects of macro,micro and simulation.Finally,the macro adhesion characteristics and micro adhesion mechanism of recycled asphalt were studied by means of contact angle and infrared spectroscopy.The main conclusions are as follows:（1）By comparing the performance of pressure aging asphalt and RAP recycled asphalt in Jiayuguan area,the representative aging asphalt sample in Northwest strong ultraviolet area is determined as the 50h simulated ultraviolet aging asphalt in laboratory.The optimum ratio of the self-made bio-oil regeneration agent was determined by orthogonal test design with basic properties as index.The results of basic indexes,Brinell rotation viscosity and rheological test of recycled asphalt show that with the increase of penetration and ductility,the softening point and Brinell rotation viscosity of recycled asphalt decrease,the rutting factor and complex shear modulus decrease,and the phase angle increases.The higher the mixing temperature,the longer the mixing time,the more the amount of regenerant,the shallower the aging degree of asphalt,the greater the penetration and ductility of recycled asphalt,the smaller the softening point and Brinell rotation viscosity,the lower the rutting factor and complex shear modulus,and the larger the phase angle.（2）The diffusion and fusion phenomenon of recycled agent and aged asphalt satisfies Fick’s law.At the initial stage of diffusion,with the increase of diffusion time,the softening point becomes lower,the corrected peak area of antisymmetric expansion of CH₂ becomes smaller,the corrected peak area of C=O and C-O expansion of saturated fatty acid ester becomes larger,the average orientation shift in MSD curve increases rapidly,the asphalt becomes soft,and the diffusion coefficient becomes larger,which indicates that the amount of diffusion fusion between regeneration agent and aging asphalt is large.But after a period of time,the diffusion rate gradually decreased.The higher the diffusion temperature is,the larger the diffusion coefficient is,which indicates that the higher the temperature is,the faster the diffusion fusion efficiency of regeneration agent and aging asphalt can be.As the aging degree of the sample gets deeper,the diffusion coefficient becomes larger,but the increasing speed becomes lower,indicating that the diffusion phenomenon continues,but the rate becomes slower.（3）After asphalt regeneration,the adhesion work,cohesive work and compatibility ratio increase gradually,while the stripping work decreases gradually,which indicates that the adhesion performance between asphalt and aggregate becomes better and the water stability of recycled asphalt becomes better.In the process of regeneration,the higher the mixing temperature and the lower the aging degree of the recycled asphalt,the better the adhesion between the recycled asphalt and the aggregate.However,the longer the mixing time and the more the amount of the regenerant,the better the adhesion between the recycled asphalt and the aggregate.In the process of asphalt regeneration,the mixing time and the amount of the regenerant should be controlled.（4）The UV aged asphalt and bio-oil regenerant are physically mixed and do not produce chemical reaction.The corrected peak areas of carbonyl and sulfoxide groups decrease after asphalt regeneration.With the increase of mixing time,mixing temperature and the amount of regenerant,the higher the aging degree of asphalt,the carbonyl correction peak area of recycled asphalt decreased,and the sulfoxide correction peak area decreased first and then increased.The adhesion performance of recycled asphalt mixture in dry condition and the spalling resistance of recycled asphalt mixture in the presence of water depend on the dispersion component of asphalt.The correlation between surface free energy index and carbonyl correction peak area in FTIR is very good.It is feasible to use carbonyl correction peak area to characterize micro adhesion mechanism of asphalt before and after regeneration.