Identification Of Aging Genes And Research Of Aging Mechanism Of Asphalt Based On Different Mixing Temperature

The aging of asphalt is an important factor affecting performance and durability of pavement.Nowadays,the researches about asphalt aging mainly based on the characterization of macro performance of specific asphalt samples.The results indicated that the change rules of macro performance of aged asphalt are basically identical,however,the anti-ageing properties of different asphalts show great difference.Furthermore,the difference of macro performance led by aging is the external appearance of micro structural changes.The molecular mechanism of asphalt aging and the aging mechanism are still unclear due to the extremely complex composition and structure of asphalt.Moreover,with the development of asphalt pavement materials construction technologies,cold,warm and extra-high mixing technologies（mixing temperature higher than 163℃）have been commonly used in asphalt mixing technologies,however,the effect of different mixing temperature on the short-term and long-term aging performance of asphalt has been unclear.Meanwhile,with the development of asphalt modification,SBS modified asphalt has been widely used in asphalt pavement,meanwhile,the effect of different SBS addition on the anti-aging properties of modified asphalt has been still unclear.Regeneration is the inverse process of asphalt aging,and the judgment of aging information is an important for judging the timing of asphalt pavement recycling,however,the process of getting asphalt pavement aging information is complex and time-consuming which ends in recycle time delay.In this paper,base on the same mixing temperature,the aging law and molecular mechanism of asphalt,the effects of different mixing temperatures and different SBS additions effects on the long-term aging properties of modified asphalt were studied.Furthermore,the key microstructures（namely as"ageing genes"）which determine the aging performance of asphalt was confirmed.After,the relationship between"ageing genes"and aging performance of asphalt were revealed.The prediction model was set up based on"ageing genes"to predict the conventional properties of asphalt.Through this paper,it helps put forward a reasonable explanation for the difference of anti-ageing properties of different asphalts,and revealing the molecular mechanism of asphalt aging and provide a quick method for judging the recycling time.In this paper,RTFOT and PAV ageing methods were used to simulate the short and long time aging stages of asphalt.Conventional properties such as penetration,soft point,rheological properties such as DSR,BBR,chemical structure determining methods such as IR,NMR,were used to evaluate the matrix asphalt from various crude oil and SBS modified asphalt with various SBS addition.The ageing genes were determined after the experiments and analysis.Partial Least Squares method（PLS）was used to build model for predicting aging behaviors of asphalt.Drawing the results of experimental tests and statistical analysis,main conclusions are as follows:According to the oil source type of asphalt,representative typical matrix asphalt samples were selected.Base on one mixing temperature,the anti-aging properties of various matrix asphalts show great difference.The penetration,softening point,ductility,60℃dynamic viscosity index had obvious advantages in evaluating the anti-aging performance of matrix asphalt among conventional properties.The results of microscopic evaluation show that the composition structure of aromatic→colloidal→asphaltene changes and oxygen elements change greatly during the aging process of asphalt.Compared with other functional groups,the content of oxygen-containing functional groups such as carbonyl and sulfoxide groups increased obviously after aging which were determined as“aging genes”.Chemomatrics was used to eliminate the mutual influence between the evaluation indicators which showed carbonyl peak area,TG residue weight ratio,TG loss ratio,oxygen content had good correlationship with SARA component,physical,rheological properties.The representative SBS modified asphalt samples were selected and prepared for short-term and different long-term aging samples.The results showed that SBS modified asphalt（4.5%SBS addition）（SBS 4.5 for short）showed lower high-performance and anti-aging properties than SBS modified asphalt（3.0%SBS addition）（SBS 3.0 for short）after the RTFOT and PAV aging.Similar with matrix asphalt,the carbonyl and sulfoxide indexes of SBS modified asphalt increased with the deepening of aging degrees.The results of IR analysis show that the carbonyl area or carbonyl index is more suitable for characterizing the aging resistance of SBS modified asphalt.Based on PCA results,properties peak area@1455cm^-1,carbonyl index I_C=O,viscosity modulus G”and penetration distinguished most in asphalt aging behaviors.The carbonyl and sulfoxide index results of the Fourier Transform Infrared Spectroscopy（FTIR）analysis,rheological and conventional properties aging index results had good correlationship.Based on the analysis of the effect of different mixing temperatures on the long-term aging performance of matrix asphalt and modified asphalt,it is found that the mixing temperature has great influence on the long-term aging performance of asphalt.When the mixing temperature reaches 183℃,the long-term anti-aging performance of asphalt materials was reduced by 20%significantly and showed lowest properties performance.The PLS aging simulation model was built based on IR testing results which had good robustness for predicting the physical and rheological properties changes during the matrix and SBS modified asphalt aging process which could provide basis for quick timing of the asphalt pavement maintenance and regeneration,the R² of predicted and measured values was more than 0.8.