Research On Asphalt Self-repairing Composite Based On Graphene Microcapsules

Bitumen is a widely used pavement material,which will be aging influencing by the environmental factors such as sunlight,rainwater scour and temperature change.It is an important task for pavement materials to reduce the pavement damage caused by bitumen aging,reduce the cost of pavement maintenance and prolong the service life of road.The bitumen itself has the capability to self-healing,which is gradually decreasing.The method of electrothermal induction and microcapsules is proved to be effective to improve the self-healing ability of bitumen material.However,the above two methods have some limitations,which limit the practical efficiency of the self-healing of the bitumen material.It is an ideal method to combine the microcapsule method with the electrothermal induction method to take into account both the advantages and the discarding of the shortcomings.The aim of this work is to prepare self-healing microcapsules with graphene/organic composite shell materials by a two-step self-assembly using a strength hexametlhoxymetlhylmelamine(HMMM)resin.First,the morphology,integrity,average size,shell thickness,microstructure and synthesis mechanism of the above microcapsules were studied.The results showed that the adhesion of graphene on the surface of the core liquid drop depends on the electrostatic attraction and the chain entanglement of macromolecules.The microstructure of the microcapsules was studied by means of SEM,XPS,EDX,TEM and AFM,which proved that the graphene and resin formed composite shell structure.It was found that the maximum amount of graphene attached to the shell material was 6.0-8.0 wt.%.The amount of graphene attached was determined by the electric charge balance.Adding different contents of graphene to the shell material will affect the morphology of the microcapsules.Thermal decomposition temperature of microcapsules with graphene had increased to about 350 ℃ with 2.0 wt.%graphene in shells.The electrical conductivity of the microcapsules with 10.0 wt.%graphene added to the shell material was about 3.8×10-2 Ω·m.Compared with the microcapsules without adding graphene,its conductivity has been greatly improved.Graphene microcapsules and bitumen were mixted to form composite materials,and it was found that the composite materials have a certain capacity of electrical and thermal conductivity.The results of infrared thermal imaging also showed that the bituminous sensitivity to heat was greatly increased due to the addition of graphene microcapsules,which proves that the asphalt composite had a certain thermal conductivity.The ice adhesion strengths of graphene microcapsule/bitumen decreased from 582 KPa to 125 KPa when low voltage was applied,which indicated that there was a certain anti-icing ability on the surface of bitumen.The self-healing efficiency of microcapsules/bitumen samples was evaluated by a beam on elastic foundation(BOEF)mechanical process under temperature of 0 ℃.It was found that the aging bitumen had an enhanced self-healing capability because of the electrothermal self-healing mechanism.This study also made a preliminary study on the electrothennal self-healing mechanism.The healing of the above-mentioned microcracks mainly depended on the fast softening and bonding of the asphalt molecules under the interface of the electrothermal action and the rapid diffusion of the rejuvenator under the action of heat.The above results provide a novel material for the self-healing of bituminous materials and will provide a new approach to the self-healing of bituminous materials.