| Asphalt is an important building material in infrastructure construction in the field of transportation.In this paper,the special behaviors of asphalt are studied by molecular dynamics simulation,including asphalt oxidation behavior and asphaltene aggregation behavior,asphalt-oxide interface adhesion,and the feasibility study of organic inorganic nano-hybrid material Ov POSS as asphalt nano-modifier,which provides a certain reference value for exploring the performance improvement mechanism of asphalt and developing new asphalt modifiers.Firstly,by building a variety of asphalt molecular models,analyzing the advantages,disadvantages and application cases of each model,it is concluded that the twelve molecule asphalt model is most suitable for verifying the characteristics of asphalt systems,the four molecule asphalt model is suitable for calculating the compatibility between asphalt components,and the twelve molecule asphalt Reax FF model is suitable for relevant research on asphalt oxidation behavior.By studying the non-bond interaction energy in asphalt system,the important influence of temperature on asphalt performance is clarified.At the same time,it is found that the molecular structure of each component in the system changes significantly after the oxidation of asphalt along with the changes of the performance of asphalt system.Secondly,this paper conducts relevant simulation research on asphaltene aggregation behavior,analyzes the influence of different parameters,different temperatures,and different component on asphaltene aggregation behavior,and constructs the relationship between asphaltene aggregation behavior and bee structure from the molecular level to analyze the formation mechanism of bee structure.It is found that asphaltene with more benzene rings,asphaltene with highly symmetrical molecular structure,asphaltene containing short branched chains or asphaltene without branched chains,asphaltene coexisting with a small amount of paraffin,asphaltene without organic solvent such as toluene,and asphalt with a high content of asphaltene（such as gel asphalt）are all prone to asphaltene aggregation.It is also found that in the asphalt system,the wax with low solubility forms crystals under the action of the molecular van der Waals force.When the asphaltene meets with the paraffin crystal,the paraffin,having the same poor compatibility,will further reduce the diffusion ability of the asphaltene,which then attracts and gathers the strong polar asphaltene on the surface of the paraffin crystal.Finally,the bright and dark stripes of bee structure are generated.Thirdly,the interface interaction between asphalt and oxide is studied.The influencing factors of interface adhesion are explored from asphalt,aggregate and environment respectively,and the failure mechanism of adhesion behavior is proposed on this basis.It is found that the adhesion of asphaltene and resin to oxide is the best.When asphaltene aggregates,the adhesion between asphaltene and oxide will decrease.Compared with the non-oxidized asphalt,the oxidized asphalt shows about 13%decrease of its interface adhesion energy with the oxide.At the same time,it is found that the breaking bond density of the aggregate surface is positively related to the asphalt-aggregate interaction strength.The temperature range of fine interfacial adhesion between asphalt and oxides is 298 to 373 K,and asphalt mixtures containing more alkaline minerals have strong resistance to water damage.Fourthly,it is the first time to explore the modification of asphalt materials by Ov POSS nanomaterials.Molecular dynamics simulation is used to explore the effect of Ov POSS on asphaltene aggregation behavior and asphalt-oxide interface adhesion,and the modification mechanism of Ov POSS on the performance of matrix asphalt and SBS modified asphalt is analyzed.There is a strong intermolecular non-bond interaction between the eight ethylene branches of Ov POSS and asphaltene molecules,which constrains asphaltene molecules and makes them not easy to aggregate.It is also found that nano-Ov POSS can improve the adhesion performance of asphalt-oxide interface.For the matrix asphalt system and SBS modified asphalt system,nano-Ov POSS can improve the non-bond interaction energy in the two systems.It is these non-bond interactions that enables nano-Ov POSS to be uniformly dispersed in the asphalt system without aggregation,makes Ov POSS nano-clusters more attractive to surrounding asphalt molecules than Si O2 nano-clusters,makes nano-Ov POSS more compatible with asphalt molecules,and enhances the compatibility between SBS and asphalt molecules.Therefore,nano-Ov POSS can better maintain the structural stability and deformation resistance of asphalt system.The unique role of the organic-inorganic nano-hybrid material Ov POSS in the asphalt system is not realized by traditional nanomaterials. |
