Effect Of Aging And Recycling On The Performance Of Asphalt And Asphalt Mixtures

With the increase in the proportion of highway maintenance in the country,the treatment of a large number of waste asphalt mixtures has become a difficult problem for highway researchers,and aging and recycling has become a hot spot for current research.The aging and recycling of asphalt materials are affected by external factors such as temperature,ultraviolet light,and time,as well as by the composition of materials such as asphalt film thickness,volume fraction of conditioning materials,and rejuvenators.Therefore,the analysis of the effects of aging and recycling on the dynamic mechanical properties and fatigue damage characteristics of asphalt materials can be used as a reference for asphalt pavement recycling and preventive maintenance work.This paper designs micron-scale film aging tests and conventional aging tests to simulate the aging of multi-scale asphalt materials under different conditions,and investigates the dynamic mechanical properties and fatigue damage characteristics of asphalt and its mastic by means of dynamic shear rheometer(DSR);Effects of different aging times,aging methods,film thickness and filler volume fraction on the dynamic mechanical properties and fatigue damage characteristics of asphalt and its mastic;Develop the asphalt regenerator independently,and study the influence law of regenerator on dynamic mechanical properties and fatigue damage characteristics of aging asphalt;combine with regenerated asphalt mixture to verify the influence of regenerator on road performance and fatigue damage characteristics of regenerated asphalt mixture.The main research findings are as follows:(1)Based on the time-temperature-aging equivalence principle,the effect of aging on the dynamic mechanical properties of asphalt and its mastic was analyzed.The results show that the complex modulus of asphalt and its mastic gradually increases and the phase angle gradually decreases with the increase of aging time;the dynamic mechanical properties of asphalt and its mastic are most obviously affected by micron-level thermal oxygen aging;the larger the volume fraction of filler in the aging process of asphalt mastic,the smaller the degree of change in the dynamic mechanical properties of asphalt mastic after aging;the aging-time shift factor change law in the aging master curve indicates that mineral powder has a certain inhibitory effect on the aging of asphalt mastic.(2)The effect of aging on the fatigue damage characteristics of asphalt and its mastic was analyzed based on viscoelastic continuum damage(VECD)theory.The results show that with the increase of aging time,the damage strain of asphalt and its mastic decreases,and the material integrity parameter gradually decreases,which leads to the increase of its damage;the fatigue life prediction results show that under low strain,aging makes the fatigue life of asphalt increase,and under high strain,aging makes the fatigue life of asphalt decrease,and the longer the aging time,the more obvious the degree of fatigue life change.(3)The effects of the rejuvenator on the dynamic mechanical properties and fatigue damage characteristics of recycled asphalt was analyzed based on the self-developed asphalt rejuvenator.The results show that the self-developed regenerator can restore the properties of aged asphalt;the addition of regenerator reduces the complex modulus of the recycled asphalt binder to a level close to that of the original asphalt;the addition of the regenerating agent reduces the complex modulus of the aged asphalt increases the phase angle and restores its dynamic mechanical properties;For fatigue damage characteristics,the regenerant increased the breaking strain,material integrity parameters and fatigue life at high strain of the recycled asphalt,restoring the resistance of the recycled asphalt to fatigue damage.(4)The recycled asphalt mixture grade was designed based on the variability analysis of Reclaimed Asphalt Pavement(RAP)aggregates to verify the effect of the regenerant on the road performance and fatigue performance of the recycled asphalt mixture.The results show that the design of multi-grade material reduces the dispersion of RAP material,and the addition of the regenerant improves the water stability and fatigue performance of the recycled asphalt mixture,but reduces its high temperature stability.