Multi-Scale Study On Aging,Regeneration Mechanism Of High Viscosity Asphalt And Its Interaction With Aggregate

With the gradual promotion of drained asphalt pavement in China,the demand for high-viscosity asphalt related research continues to grow.Compared with ordinary asphalt pavement,the drainage pavement has a large pore structure and is often in a watery environment.As a result,the high-viscosity asphalt in the drainage pavement is more susceptible to aging due to the coupling effect of oxygen,moisture,ultraviolet rays and other factors.The aging mechanism of high-viscosity asphalt under the coupling action of single or multiple environmental factors still lacks exploration at the molecular and chemical perspectives.The regeneration of drainage pavement is in its infancy in China,and there are relatively few studies on the regeneration of aged highviscosity asphalt.In addition to the regeneration of the asphalt phase,the restoration of the high-viscosity characteristics and the corresponding components is the key factor to improve the regeneration effect of the drainage pavement.Compared with ordinary asphalt mixtures,the high-viscosity asphalt-aggregate interface in drained asphalt mixtures is more prone to failure due to long-term erosion by dynamic water and infiltration of hydrostatic water.Clarifying the interaction mechanism of the interface between the original,aged and recycled high-viscosity asphalt and aggregate can provide a theoretical basis for ensuring and prolonging the service life of drainage pavement.This dissertation combines the multi-scale research methods of macro and micro experiments,molecular dynamics simulation and quantum chemical calculation to study the modification mechanism,aging mechanism,regeneration mechanism and interface effect of SBS type high-viscosity asphalt,and the results can provide a theoretical basis for the application and regeneration of the drainage pavement.The main works of this dissertation are as follows:(1)The multi-scale modification mechanism of high-viscosity asphalt was carried out combined with macro and micro experiments and molecular dynamics simulation.Firstly,based on the penetration,ductility,softening point,viscosity and the change trend of high and low temperature properties,the appropriate high-viscosity modifier content was selected.Secondly,based on the test results of infrared spectroscopy,fluorescence microscopy,scanning electron microscopy and gel chromatography,the microscopic changes of asphalt under the action of high viscosity modifier were analyzed.Finally,based on the measured results of the principal components,the molecular model of the high-viscosity modifier was constructed,and molecular dynamics simulation was carried out to study the interaction between high-viscosity modifier and asphalt from four aspects: compatibility,system stability,diffusion uniformity and distribution aggregation.The action of mineral oil components in highviscosity modifier in high-temperature preparation and normal temperature road use was also analyzed.(2)Multi-scale studies on the properties and structural changes of high-viscosity asphalt during aging and its mechanism are carried out combined with macro and micro experiments,molecular dynamics simulations and quantum chemical calculations.Firstly,based on macroscopic tests,the effects of thermal-oxidative aging on the penetration,ductility,softening point,viscosity and high and low temperature properties of high-viscosity asphalt were analyzed.Appearance change of highviscosity modifier and its solubility in tetrahydrofuran after thermo-oxidative aging alone was studied,the degradation characteristics of the polymer phase in the highviscosity modifier after aging was also analyzed by infrared spectroscopy and gel chromatography experiments.Secondly,the microscopic characteristics of the highviscosity modifier phase and the asphalt phase were studied after thermal-oxidative aging of high-viscosity asphalt based on microscopic experiments of Fourier transform infrared spectroscopy,fluorescence microscopy,scanning electron microscopy and gel chromatography.After that,first-principles calculations were carried out by using density functional theory based on quantum chemical methods,and the aging reaction sites,sequences and products of asphalt molecules and high-viscosity modifier molecules under the action of oxygen,moisture,ultraviolet single aging field and multifield coupling are studied.Finally,molecular models of light,medium and heavy aged high-viscosity asphalt were constructed to simulate the component compatibility and asphaltene aggregation properties in the aged high-viscosity asphalt,as well as the hydrogen bond distribution in the high-viscosity asphalt-water system and the diffusion state of oxygen and water molecules in the high-viscosity asphalt.(3)Multi-scale studies on the regeneration of high-viscosity asphalt were combined with macro and micro experiments and molecular dynamics simulations.Firstly,the difference between the diffusion stage of the rejuvenator to the aged highviscosity asphalt in central plant hot recycling and hot-in-place recycling is analyzed,and the temperature field of the diffusion stage of the rejuvenator is determined based on the finite element heat transfer simulation and engineering experience.Secondly,a time-domain inverse heating method was proposed to prepare the samples of the rejuvenator diffusing into the aged high-viscosity asphalt.Based on the characteristic peak area index of viscosity and infrared spectrum,the diffusion ratio of rejuvenator in high-viscosity asphalt was calculated,and the influence of regeneration method and regeneration position on the diffusion inhomogeneity of rejuvenator was analyzed.After that,the molecular models of the slightly and severely aged high-viscosity asphalt and the representative components of the three rejuvenators were selected.A segmented temperature fitting method was proposed to set the temperature field in the molecular dynamics simulation,and the relationship of interdiffusion and miscibility between the rejuvenator and the virgin and aged high-viscosity asphalt was clarified.Finally,the concept of high-viscosity modifier-recycled high-viscosity asphalt was proposed,and the macroscopic properties of recycled high-viscosity asphalt and the repairing effect on microstructure were studied by adding high-viscosity modifier.(4)Multi-scale studies on the interfacial interaction of high viscosity asphaltaggregate were carried out combined with macro and micro experiments and molecular dynamics simulations.Firstly,the pull-out strength between virgin,aged and regenerated high-viscosity asphalt and acid-base aggregates,as well as the spalling rate of high-viscosity asphalt on the surface of aggregates under boiled conditions were tested.Secondly,the adhesion work and debonding work between the original,aged and regenerated high-viscosity asphalt and acid-base aggregates,as well as the interfacial debonding resistance index ER,were calculated by the sessile drop method.The adhesion state in the presence of water,as well as the resistance to water damage,and the correlation of the macro and micro test results were analyzed.Finally,molecular dynamics simulations were carried out to analyze the interfacial adhesion mechanism between the virgin,aged and regenerated high-viscosity asphalt and representative components of aggregates with and without water from the perspectives of interaction energy,nanoindentation force,and hydrogen bond distribution.