Research On Multi-scale Evaluation Of Fusion Behavior Of New And Old Asphalt

Nowadays,tens of thousands of tons of waste asphalt mixture(RAP)is not recycled and reused after being milled,and is accumulated and discarded,causing loss of resources and destruction of the ecological environment.One of the important reasons for this is that the fusion behavior,fusion process,fusion state and degree of fusion of the new and old asphalt in the research of recycled asphalt mixtures have not been quantitatively evaluated.The fusion change law of the new and old asphalt and the micromechanical properties of the new and old asphalt fusion have not been studied in depth.Therefore,based on the macro,meso and nano-micro and other multi-scale areas,this paper analyzes and studies the fusion change law of the new and old asphalt,the mechanical properties of the fusion of the new and old asphalt,and improves and proposes the quantitative evaluation index of the fusion degree of the new and old asphalt,which enriches the recycling and utilization of asphalt.The theoretical basis of this paper provides important scientific research significance for follow-up research.First,select the asphalt combination material of No.90 base asphalt + No.70 old asphalt,use three tracers of SBS,rubber powder,and epoxy resin to analyze the fluorescence image of the old asphalt with the tracer with the aid of a fluorescence microscope test instrument.In the comparative analysis of the three tracers,epoxy resin was finally selected as the tracer,and then the Image-Pro Plus image analysis software was used to use the average optical density(MOD),average gray value(MGV),and cumulative optical density(IOD)Three optical parameters were used to quantitatively analyze the fluorescence image.The results found that the optical parameters of the two materials are quite different,and it shows that the two-phase materials are fused,and the overall fusion degree is relatively high,but local mixing Inhomogeneous,there is a quantification of the degree of fusion.Secondly,three asphalt combinations of No.70 base asphalt + No.70 old asphalt,No.90 base asphalt + No.90 old asphalt,SBS modified asphalt + No.70 old asphalt are selected,and the oxygen content in the recycled asphalt combination is measured by the infrared spectrum test instrument.The functional group carbonyl(C=O)and sulfoxide group(S=O)were analyzed,and the analysis concluded that with the increase of the content of aging asphalt,the carbonyl index and sulfoxide group index in the new and old regenerated asphalt increased to varying degrees.It can be seen from the image analysis that in the process of fusion of old and new recycled asphalt,the speed of fusion in the early stage is faster than that in the later stage.Next,with the aid of atomic force microscope microscopic instruments,the twodimensional height scan and the three-dimensional height scan in the Nano Scope Analysis image analysis software were used to analyze the microscopic fusion law of the new and old asphalt combinations of the three asphalt combinations.It was found that:As the increase,the number of "bee" structures of recycled asphalt is gradually reduced;the average roughness(Ra),the root mean square of height(Rq),and the difference between the maximum and minimum height(Rmax)are used to reflect the fusion of asphalt.With the increase of the new asphalt content,the three types of indicators are all smaller than the weighted value;based on the PFT-QNM force curve working mode,the nanoindentation test data is calculated through the Sneddon model,and the conclusion is drawn: The increase in the content of the old asphalt and the increase in the elastic modulus of the asphalt combination to different degrees indicate that the new and old asphalt has indeed merged,and the penetration and fusion effect is carried out in two directions.Finally,the traditional asphalt performance verification method was used to verify the fusion behavior of the new and old asphalt under the three asphalt combinations.With the aid of the two-layer asphalt model,the fusion degree of the new and old asphalt is quantitatively analyzed based on the DSR single-point scanning mode,and then the influencing factors of the fusion degree are studied based on the range method in the orthogonal test,and finally the degree of fusion is obtained in different asphalts.Combination,different adjustment time,different adjustment temperature and the relationship under different aging degrees,it is found that the most influential of the three factors is the adjustment temperature.With the help of the indoor universal testing machine and the analysis of the results of the pull-out test on the bonding performance of the three asphalt combinations,it is concluded that the bonding strength of the matrix asphalt is greater than that of the recycled asphalt and much greater than that of the aged asphalt.The bond strength of the asphalt sample is constantly weakening,and the bond strength of the three combinations is roughly SBS modified asphalt + No.70 aged asphalt>No.90 base asphalt + No.70 aged asphalt> No.70 base asphalt + No.70 For aged asphalt,the linear correlation between the content of aged asphalt and the bonding strength in the three combinations is good.