Study On The Adhesion Failure Of Asphalt-aggregate Interface Under Water Effect

The asphalt pavement is easy to occur loose,sink and pit during the use of transportation.The appearance of these road diseases is often accompanied by the moisture effect,which greatly decline the service life and safety performance of asphalt pavements.The water damage of asphalt mixture is caused by relative displacement and friction of aggregate under the repeated action of vehicle load,which punctures or abrades the asphalt film.This makes it easy for the external water entering the asphalt mixture from the void to invade the aggregate surface through the cracking position of the asphalt film,forming moisture film to replace asphalt film,which lead to the failure of the adhesion capacity between asphalt and aggregate.Therefore,it is necessary to deeply understand the water damage process caused by water intrusion from asphalt film crack,study the strength deterioration law of water on asphalt-aggregate interface,modify asphalt-aggregate interface to reduce the impact on water diffusion in interface,decrease the water damage of asphalt mixture,improve the service life and safety performance of pavement.First of all,in this paper,the pull-out test was used to study the effect of different immersion times at normal temperature on the adhesion capacity between 70# base asphalt and acid aggregate granite or alkaline aggregate limestone.The results indicate that the adhesion ability between asphalt and granite or limestone is better at dry condition.However,as the increase of immersion time of asphalt-aggregate interface specimens,the pull-out strength and the adhesion capacity between asphalt and aggregate decreased.Meanwhile,due to the moisture peeling off asphalt film from aggregate surface,the morphology of the asphalt-aggregate interface has also changed.The asphalt-granite interface is the most seriously affected by water erosion,and its water damage resistance is weaker than that of the asphalt-limestone interface.Secondly,hyperspectral image technique was adopted to accurately identify and nondestructive detect the mineral composition and distribution on the surface of granite and limestone.The main component of the selected granite is albite and the main component of limestone is calcite.Finally,the molecular dynamics was employed to study the changes of asphalt structure,the distribution,concentration and diffusion of asphalt components on aggregate surface,and the adhesion ability modification between asphalt and aggregate before and after the intrusion of external moisture from atomic scale.The targeted method to improve the water stability of asphalt-acid aggregate interface was proposed.The results show that the effect of interfacial moisture makes the distribution of asphalt components on the aggregate surface more uniform,significantly reduces the concentration of asphaltene and resin,and improves the diffusion rate of light components and resin.As a result,the asphalt structure and interface microstructure are modified and the adhesion capacity between asphalt and aggregate is decreased.In water environment,the debonding energy absolute value of asphalt-calcite interface is greater than that of asphalt-albite interface,this means that the water damage resistance of the asphalt-calcite interface is greater than that of the asphalt-albite interface.For asphalt-acid aggregate interface,silane coupling agent(SCA)can be added into asphalt to effectively enhance the water damage resistance of the interface.