Study On Aging Kinetics Of Asphalt Under The Weathered Action

Asphalt aging can change its molecular structure and affect its mechanical properties.In this paper,the ultraviolet radiation,air velocity,air humidity,illumination intensity and moisture content of asphalt pavement are monitored to determine the parameters required for the test.The asphalt aging in practice is simulated by the improved indoor full-climate aging accelerator.The aging dynamics of asphalt is studied from both micro and macro levels.Dynamics.Through the above research,the following conclusions are drawn:Fourier transform infrared spectroscopy?FT-IR?experiments showed that the number of sulfoxide and carbonyl groups of asphalt increased with aging time,indicating that asphalt was mainly oxidized with oxygen.Differential scanning calorimetry?DSC?experimental study showed that with the increase of asphalt aging time,the glass transition temperature gradually increased and the low temperature performance decreased.Gel permeation chromatography?GPC?test was carried out.It is found that the molecular distribution of aged asphalt is more concentrated when the aged asphalt aggregates into macromolecule from small molecule;the bond strength of asphalt and its adhesion to coarse aggregate decrease with the increase of aging time in drawing test and adhesion test;the Brinell viscosity and dynamic viscosity of asphalt increase nonlinearly with the increase of aging time;and the dynamic shear rheology of asphalt increases nonlinearly with the increase of aging time.?DSR?test found that with the increase of aging time,the complex modulus of asphalt increased significantly,the phase angle decreased significantly,and the high temperature performance of asphalt increased significantly under the action of temperature scanning.The fatigue performance of asphalt decreased gradually with the increase of aging time,and the fatigue performance of simulated asphalt decreased nearly 3/5 after about three years of service.In the study of micro-dynamics,Petersen's theory is used to establish the general dynamic equation of asphalt micro-aging:f?t?=Lf₀/[1+?L-1?e^-at].It describes the dynamic relationship between the change of asphalt Micro-properties and the aging time of the whole climate.The results show that the final amount of carbonyl and sulfoxide produced by asphalt during its theoretical complete aging is 1.206 and 1.773times of the carbonyl and sulfoxide content in the base asphalt,i.e.asphalt aging.The formation rate of macromolecule is consistent with that of small molecule,and the change of molecular weight accounts for about 2%of the total number of asphalt molecules.The experimental parameters alpha and L represent the aging reaction rate and degree,respectively.The micro-aging kinetic equation obtained by non-linear fitting has good correlation and high reliability,and can be used to predict the whole climate well.Microdynamic properties of asphalt aging under action.In the study of macrokinetics,based on the homogeneous system theory?asphalt internal dispersion is uniform,asphalt aging is uniform aging of the whole asphalt?and the Arenus equation,the reaction activation energy is introduced,and the general equation of asphalt aging at macro level is established as follows:lnc_t/c₀=aexp?-E/RT?t=kt.The results show that the reliability index of the equation based on softening point is as high as 0.98,while that based on ductility is as low as 0.89,which shows that the softening point index can better reflect the performance of asphalt after aging than the ductility and penetration index.There is a non-linear relationship between the rotational viscosity and the aging time and test temperature of asphalt,and the viscosity increases with the aging time.The rutting factor has a non-linear relationship with the aging time and temperature of asphalt,which increases with the aging time and decreases with the aging temperature.The multi-stress creep?MSCR?-elastic parameters have a non-linear relationship with the aging time and stress level of asphalt,and increase with the aging time,while the asphalt MSCR-viscous.The experimental parameters?R and T are molar gas constants and thermodynamic temperature respectively?E and K represent activation energy and rate constant of aging reaction respectively.The macroscopic aging kinetics equation obtained by non-linear fitting has good correlation,high reliability and performance.It can be used to predict the macro-dynamic properties of asphalt aging under the whole climate.