Research Of Self-healing Characteristics Of Recycled Asphalt And Micro Analysis

As a typical viscoelastic material,asphalt can repair its own damage to prolong its service life.However,the asphalt will gradually be aged in the long-term using process,asphalt’s normal road performance and self-healing performance will be deteriorated in this process,we can restore this effect by adding regenerant.However,the research on the self-healing properties of regenerated asphalt is insufficient at present.This paper mainly considers the three factors of asphalt aging degree,types of regenerant and the amount of regenerant in the process of preparing recycled asphalt,the conventional properties,rheological properties,self-healing properties and chemical properties of fresh asphalt,aged asphalt and recycled asphalt are systematically studied through dynamic shear rheology test,infrared spectroscopy,gel chromatography and other methods.The main research results are as follows:（1）As the temperature rises,the flow performance of the asphalt is enhanced,and the flow behavior index n gradually increases.When n=0.9,the asphalt reaches a near Newtonian fluid state,continued warming is not obvious for the improvement of asphalt flow performance;the flow performance of the aged asphalt is significantly improved after the addition of the regenerant,and the flow behavior index n increases,the corresponding temperature decreases when the temperature reaches near Newtonian state.（2）The self-healing model based on the diffusion theory can quantitatively describe the increasing trend of the bitumen healing index with the healing time.The self-healing performance of the aged asphalt is restored after being regenerated.The trend is opposite to the asphalt aging process.Among these indicators,the healing index(_（6）has a good correlation with the indicators such as viscosity,flow behavior index and rutting factor,and it is feasible to estimate the asphalt healing index based on the change of the rheological index during the process of asphalt aging and regeneration.（3）As the healing temperature and time increase,the bitumen healing index shows an increasing trend from fast to slow,indicating that there existence an optimal condition to heal asphalt,and the effect of aging and regeneration on the optimal healing conditions of asphalt is mainly at temperature,The optimal healing temperature of recycled asphalt is significantly lower than aged asphalt.In addition,compared with different temperature thresholds of asphalt,it is found that the softening point of asphalt or the temperature at which it reaches a near newtonian fluid state can be taken as the optimal healing temperature.（4）Analyzed the influence of asphalt aging degree,types of regenerant and regenerant dosage on the performance of reclaimed asphalt by conventional indexes,rheological indexes and self-healing indexes.The results show that the performance of lightly aged asphalt is relatively easy to recover,and the performance of regenerated asphalt increases with the increase of the amount of regenerant.The regenerative effects of the three regenerators on the aged asphalt are:Y>S>R.（5）Analyzed the chemical properties of asphalt in different states by infrared spectroscopy（FTIR）and gel chromatography（GPC）,The regeneration agent can reduce the content of polar oxides in the aging asphalt through physical dilution,adjust the molecular weight distribution,and restore the movement ability of the asphalt molecules.The results of the study show that the chemical properties of relatively light aged asphalt are relatively easy to recover.increase the amount of regenerant has a greater effect on the chemical properties of aged asphalt.the effects of the three regenerators on the chemical properties of aged asphalt are different,but none of them can restore the chemical properties of aged asphalt to the original asphalt level.（6）Analyzed the correlation between asphalt self-healing index and micro-chemical index.The results show that the type of regenerant will affect the correlation between asphalt self-healing index and micro-chemical index.The self-healing index of asphalt has a good correspondence with the content of small molecules,sulfoxide and carbonyl functional groups.The self-healing properties of asphalt during aging and regeneration are sensitive to small molecular weight and polar functional groups.