Study On The Deterioration Mechanism Of Asphalt-aggregate Interface Performance Based On Water Diffusion

Water damage is one of the forms of asphalt pavement early damage,under the repeated action of traffic load,the relative displacement and friction of pavement materials,making it easy for water to invade the surface layer of the aggregate through the location where the asphalt film rupture occurs and produce water diffusion,and eventually replace the asphalt film with a water film,reducing the adhesion of the interface between asphalt-aggregate,asphalt pavement performance decline,and even cause serious travel safety hazards.At present,the understanding of the process and mechanism of water damage caused by water intrusion into the interface layer is not clear.The purpose of this paper is to carry out the study of water diffusion behavior on the deterioration mechanism of asphalt-aggregate interface,and to provide a basis for the study of water damage of asphalt mixture.Firstly,by conducting pullout tests on asphalt-aggregate specimens under different water bath times,the ultimate load at the time of specimen damage was obtained,and two evaluation indexes,pullout strength and pullout strength ratio,were used to analyze the test data and reveal the change law of adhesion performance of moisture intrusion into the asphalt-aggregate interface.The results show that the adhesion performance of asphalt-granite interface is significantly weaker than that of asphalt-phlogopite interface under wet environment;with the increase of water bath time,the damage form of asphalt-aggregate interface transitions from cohesive damage to adhesion damage.Secondly,ABAQUS finite element modeling was completed by generating zerothickness cohesive cells to obtain the fine-scale water loss law of interfacial bonding performance before and after asphalt aging and under different combinations of conditions for both aggregates by coupling the moisture diffusion concentration field and force.The results show that with increasing diffusion time,the asphalt-aggregate resistance to external forces becomes weaker and weaker,and the bonding performance between them becomes worse;when the moisture diffusion time gradually increases,the bonding performance of pyrochlore and asphalt is significantly better than the bonding performance of granite and asphalt.Immediately afterwards,the mineral composition of two common pavement aggregates,granite and gabbro,was accurately and quickly identified using a combination of fully automated comprehensive mineral analysis technology(TIMA)and hyperspectral imaging technology,and the distribution patterns and contents of different mineral components on the surface of the aggregates were analyzed.The results show that the main components of granite are quartz,mica and feldspar,and the main components of gabbro are sodium feldspar,orthoclase and plagioclase,and the mutual interference between sodium feldspar and orthoclase is found when using ENVI software for hyperspectral imaging analysis.Finally,the combination of micro-area X-ray fluorescence spectroscopy(μ-XRF)and sodium chloride solution permeation method was used to characterize the water migration signal by elemental Cl.The water diffusion path was traced according to the energy spectrum signal of elemental Cl identified by μ-XRF,and the results showed that the diffusion path deepened gradually with the increase of diffusion time,and the diffusion path of water on the surface of granite was characterized by elemental Cl.It was found that the element was easy to adhere to the mineral like black mica and also easy to accumulate in the rough grooves.