| A variety of diseases caused by asphalt aging not only shortened the service life of asphalt pavement,but also improved the maintenance cost of asphalt pavement,which seriously affected the smooth and driving safety of transportation.The degree of aging of asphalt,physical changes in aging,micro-structure changes,and resistance to high temperature deformation capabilities have significant practical significance for the research of asphalt aging properties and reduced asphalt pavement.In this paper,two 70#matrix asphalt and the SBS modified asphalt prepared by them have been carried out at different times by rotating thin film oven test（RTFOT）and pressure aging vessel（PAV）test.In this paper,two kinds of 70#matrix asphalt and two kinds of SBS modified asphalt commonly used in asphalt pavement were tested by RTFOT and PAV aging.Based on FTIR,the evolution law of physical properties,microstructure and rheological properties of asphalt during thermal oxidation aging was studied.Based on the grey entropy correlation mathematical model,the high temperature aging prediction equation with the upper limit temperature value TPG of PG as the parameter is established.The influence of aging on the pavement performance of asphalt mixture was analyzed.Finally,the fatigue life prediction model of asphalt aging time history and fatigue life was established and verified by FTIR and PCA,which laid a theoretical foundation for the establishment of the aging performance evaluation system of asphalt pavement.The main achievements are as follows:（1）After aging,the softening point of TPC70#asphalt increases the most,followed by SBS-2 modified asphalt and JL70#asphalt,and SBS-1 asphalt increases the least,indicating that SBS-1 asphalt has the strongest anti-aging performance and TPC70#asphalt has the worst anti-aging performance.With the deepening of aging,the penetration and ductility of two kinds of 70#matrix asphalt tend to be close;Penetration and ductility of the two SBS modified asphalts also tend to be close,and the penetration and ductility of SBS modified asphalt after aging are smaller than those of 70#base asphalt,which indicates that adding SBS modifier can obviously improve the aging performance of asphalt.The relationship between viscosity at 135℃and RTFOT aging time can be described by linear relationship.（2）By comparing the infrared spectra of 70#matrix asphalt and modified asphalt,it is found that 70#matrix asphalt and modified asphalt can be distinguished by the presence or lack of characteristic absorption peaks at 700cm-1and 967cm-1,which is of great significance for the study of matrix asphalt and modified asphalt type discrimination.The functional group indices of each sample were calculated using A1basis(the peak area sum in the range of 650～1400cm-1).It was found that the functional group indices of the two asphalt substrates were very close,indicating that their saturated content,aromatic content,gum and asphaltene content were relatively close.Sulfoxide group and carbonyl group can reflect asphalt aging degree to a certain extent.Analyzes the four kinds of asphalt aging index（IA）and the relationship between the aging time,the asphalt aging degree curve drawing,goodness-of-fit R2were greater than 0.91,among them,the SBS-1 the linear fitting that the asphalt is as high as 0.9815,therefore,according to the index of the asphalt aging IAget fitting curve equation can predict to some extent asphalt aging schedule.The unrecovered creep compliance Jnrand recovery rate R are used to evaluate the ability of asphalt to resist high temperature deformation.it is found that the ability of modified asphalt to resist permanent deformation and high temperature is still significantly better than that of matrix asphalt,which is consistent with the analysis results of unaged asphalt samples,and the order of high temperature deformation resistance of four kinds of asphalt is SBS-2>SBS-1>TPC70#>JL70#.The predicted model of the asphalt index and the unrecoverable creep soft amount Jnrand the recovery rate R were established.The correlation coefficient was high,and the F test was passed,and finally the credibility of the model was verified.It indicated that the asphalt aging was high temperature resistance.The variation of the deformation capability and the chemical functional group exhibits a plurality of linear relationships,and the high temperature rheological properties of aging asphalt can be predicted by quantitative analysis by attenuating total reflection infrared spectroscopy.（3）The four components of the two 70#matrix asphalt aging were analyzed and the colloidal structure change.The JL70#asphaltene increase rate was higher than that of TPC70#slow,and the JL70#colloidal index ICwas lower than TPC70#asphalt,indicating JL70#The colloidal structure after asphalt is relatively stable than TPC70#asphalt,and its anti-aging ability is also better than TPC70#asphalt.Aging enhances the high-temperature stability of asphalt mixture,and significantly attenuates the low-temperature performance and water stability of asphalt mixture,which shows that the low-temperature stiffness increases,the deformability decreases significantly,and the hydrophilicity increases,which accelerates the water damage.Based on the grey entropy correlation mathematical model,the correlation degree between asphalt high temperature index and characteristic functional group index was discussed.The Verhulst mathematical model and 1st Opt data nonlinear fitting software were used to perform nonlinear fitting on the PG grading test results,and a high temperature aging prediction model with the upper PG temperature value TPGas the parameter was established.The correlation between the calculated value and the measured value of the TPGequation is good,and it has certain reliability.（4）Combined with FTIR technology and principal component analysis（PCA）,two principal component factors were found,which were defined as oxidation factor PCA1and component change factor PCA2.Based on the comprehensive index F of factor comprehensive evaluation,the prediction model of asphalt aging time history is established and verified,which realizes the rapid prediction of asphalt aging time history to a certain extent.Finally,the fatigue life of asphalt based on four different evaluation indexes is compared.The results show that NDER,NRDRand NGunderestimate the fatigue life to a certain extent,and NRDEC,which takes the change rate of dissipation energy RDEC as the evaluation index,is closest to the re al fatigue life of asphalt.With NRDECas the evaluation index of fatigue life,the order of fatigue life of four kinds of asphalt is SBS-1>SBS-2>JL70#>TPC70#,and NRDECis exponentially related to aging time.on this basis,the prediction model of asphalt fatigue life is established. |
