Study On The Blending Behavior Of Aged And Virgin Asphalt In Process Of Hot Recycling

In this paper,the blending behavior of aged and virgin asphalt in process of hot recycling is studied.First,the determination of the component of asphalt before and after aging differences and changes the component of the asphalt recycling in the micro level,proposed asphalt aging are essentially the directional transfer of asphalt components,asphalt recycling essence is restored to the level before aging of asphalt component,the blending behavior of aged and virgin asphalt in process of hot recycling is important factor affecting the regeneration and restore of aging asphalt in hot recycled project.In order to quantify the blending behavior of aged and virgin asphalt in process of hot recycling,a test method was designed to determine the blending degree of aged and virgin asphalt during process of hot recycling.The method using magnetite aggregate instead of new aggregate realize RAP and new material separation of hot recycled asphalt mixture.The method of "toluene immersion-standing" was used to separate the aggregate and the asphalt in the hot recycled asphalt mixture.The component changes of asphalt during hot recycling were analyzed by thin-layer chromatography with flame ionization detection(TLCFID).The formula for calculating the blending degree of aged and virgin asphalt is proposed.The test method is verified and the results show that the method can accurately and effectively determine the blending degree of aged and virgin asphalt in the process of hot recycling.On the basis of the above method,the effects of the mixing amount of RAP,mixing sequence,mixing time,mixing amount of recycling agent,mixing temperature and asphalt amount on the blending degree of aged and virgin asphalt were studied,and the blending law of aged and virgin asphalt was obtained.The results show that each factor has a significant influence on the degree of aged and virgin asphalt blending.The blending degree of aged and virgin asphalt decreases with the increase of oil film thickness.Virgin asphalt and RAP were firstly mixed,and then new aggregate was added to mix.The mixing order of 180 s was mixed,and the blending degree of aged and virgin asphalt was the largest.When the mixing ratio,mixing temperature and mixing time of aged and virgin asphalt increased,the blending degree of aged and virgin asphalt increased.When there are adverse mixing conditions such as low mixing temperature,short mixing time or low mixing amount of recycling agent,the blending degree of aged and virgin asphalt is only 10%?30%.Considering the actual production mixing conditions,the blending degree of aged and virgin asphalt can be increased to 60%?70% by adjusting the influencing factors.Finally,according to the blending law of aged and virgin asphalt,the mixing process of hot recycling was optimized,and the correlation between the blending degree of old and new asphalt and road performance was obtained by comparing the mixing process of general condition and the mixing process under adverse condition.The results show that the blending degree of aged and virgin asphalt is significantly correlated with the road performance of hot recycled asphalt mixture.When the blending degree of aged and virgin asphalt is high,the pavement performance of hot recycled asphalt mixture is better,especially the improvement of low temperature and fatigue properties is obvious.