Study On The Regeneration Efficiency Of RAP Asphalt In Thermal Regeneration Mixture

Nowadays,my country’s highways are already at the peak of large and medium repair.Disposal of the waste asphalt mixture produced by milling of the old pavement at will,firstly causing material waste,and secondly destroying the local ecology.Therefore,asphalt pavement recycling technology is of great significance to sustainable development.This article focuses on the plant-mix hot regeneration technology and the effective regeneration efficiency of the aged asphalt in RAP.RAP does not act as a "black stone" in the thermal regeneration process,but the aged asphalt in RAP is not fully utilized,but is somewhere in between.In order to study how much aged asphalt in RAP is not "blackstone",this paper defines the regeneration efficiency of RAP asphalt: the ratio of the old asphalt used in RAP to all old asphalt.However,how much old asphalt is involved in the regeneration process cannot be directly measured.Therefore,the relationship between the effective old asphalt content and the DSR test is established.The effective old asphalt content is calculated indirectly based on the DSR test results,and the regeneration efficiency of RAP asphalt is calculated according to the formula.Through experiments,the effects of different RAP content,mixing time and regenerant on the regeneration efficiency were studied.The experimental results show that when the RAP content is 20% or less,the regeneration efficiency of the old asphalt is higher,and the regeneration efficiency decreases with the increase of the content.When the content is 50%,the regeneration efficiency of the old asphalt is only 51%.The mixing time will also have a certain impact on the regeneration efficiency.Among them,the dry mixing time of RAP and the new aggregate has a limited impact on the regeneration efficiency,and the wet mixing time after adding asphalt has a greater impact on the regeneration efficiency.Different regenerants also have differences in the regeneration efficiency of RAP.Regenerants with more light components and low viscosity are more likely to stimulate the asphalt in RAP.However,the nature of the regenerant must be stable so that it cannot easily volatile and initiate regeneration during the mixing process.During the process of adding the regenerant,there will be a part of loss and uneven dispersion.Therefore,if the regenerant is added to the new asphalt in advance,the mixed mixture will have a higher regeneration efficiency of the old asphalt,but this method is more complicated.,And long-term storage of the regenerant in the new asphalt is easy to volatilize the light components,which will weaken the regeneration effect.In this paper,AC-20 hot reclaimed asphalt mixture with three RAP content of 20%,30% and 40% is selected.In order to simulate the 100% utilization of the old asphalt,all the asphalt in the RAP was extracted and mixed with the new asphalt and then mixed with the aggregate to make it.The Marshall test was performed to determine the best oil-stone ratio.Remix RAP,new aggregate and new asphalt with the same gradation and the best oil-stone ratio.By changing the mixing time,the mixture of different old asphalt regeneration efficiency is obtained and its road performance is tested.The regeneration efficiencies of different mixing times at different mixing rates are 70%～90%,65%～82%and 61%～76%,respectively.The experimental results show that the high temperature performance continues to decrease with the increase of the regeneration efficiency.When the regeneration efficiency is 100%,the dynamic stability is the lowest.After adding the regeneration agent,the dynamic stability is reduced due to the lubrication and softening effect of the regeneration agent.Low temperature performance and resistance to water damage are gradually improved as the regeneration efficiency increases.When the RAP content is 40%,the maximum flexural strain of the mixture is less than 2000(με).The addition of regenerant can effectively improve the low temperature performance,and the CA regenerant has the best effect.good.For mixtures with 30% and 40% RAP content,when the regeneration efficiency is low,the water stability does not meet the specification requirements.After the regeneration efficiency is improved,the freeze-thaw splitting tensile strength ratio and the stability of the residual water immersion are greatly improved.After adding CA regenerant,the water stability is the best.On the whole,the larger the RAP content,the better the high temperature performance of the mixture,but the worse the low temperature performance and water stability.