Molecular Dynamics Simulation Of Mass Transfer Mechanism Between Chemical Composition Of Aggregate And Emulsifier

The emulsification condition of emulsified asphalt is not controllable,so there are many obstacles in the application of emulsified asphalt,the demulsification of emulsified asphalt has been an important issue in the field of pavement material science.However,at present,the related theories are focused on the study of emulsifier to analyze the demulsification mechanism,many researchers in solving this problem.It is often more focused on the performance of emulsified asphalt on its practical application,while ignoring the other major components of asphalt mixture-aggregate.This paper starts from the mechanism of aggregate and asphalt emulsion,by molecular dynamics simulation,focusing on the chemical composition of aggregate,asphalt emulsion in key components of emulsifiers in the mass transfer mechanism of aggregate surface chemical composition,focuses on the study of the concentration of emulsifier,types and different types of aggregate effect of chemical composition on interfacial mass transfer and to provide theoretical support for the realization of the initial mixture of emulsified asphalt demulsification conditions controllable material engineering application.Based on the interface model of five kinds of chemical components in the aggregate,the interface model of the emulsifier?solution?system was compared.It is concluded that the molecular structure of emulsifier changes on the surface of the chemical composition of the aggregate,the surface changes of MgO,Ca O and SiO₂ were not obvious,but the surface of Fe₂O₃ and Al2O₃ changed significantly.Moreover,there are differences in the structure of the two emulsifiers.The lipophilic group of SDBS is adsorbed on the surface of the chemical composition of the aggregate,while the hydrophilic surface is far from the surface;the hydrophilic and surface chemical composition of CTAC adsorbed on the surface,while the lipophilic group was far from the surface.Based on the dynamic operation after generating optimal adsorption state model of emulsifier?solution?system in operation in the interface potential model system of aggregate surface chemical composition,the interaction energy calculated interface parameters.The results showed that the adsorption of emulsifier?solution?system in the contact with the chemical composition of the aggregate had a certain adsorption.At the same time,the adsorption capacity of the three groups of different emulsifier solution system on the surface of the chemical composition of the,the adsorption capacity of the same trend,are shown as: SiO₂<MgO< CaO< Fe₂O₃< Al2O₃.Moreover,the interfacial energies of SiO₂,MgO and CaO are small and the difference is slight,but the interface effect between Fe₂O₃ and Al2O₃ is very obvious,and there is a strong adsorption effect.At the same concentration of emulsifier,the interfacial effect on the surface of the chemical composition of the polymer is only when the emulsifier molecules are included,Compared with the low concentration emulsifier solution system,the concentration of the surfactant solution is higher than that of the low concentration emulsifier solution system.Based on the dynamic computation model trajectory generated interface file,select the interface model of the layer structure,emulsifier emulsifier hydrophilic?Na+ and Cl-?,and S and N atoms were the mean square displacement curve calculation.At the same time,the diffusion coefficient is analyzed by cluster analysis.The results show that when the emulsifier molecules directly contact with the surface of the chemical composition of the aggregate,the diffusion is much smaller than that of the emulsifier solution,but the overall trend is SiO₂>MgO>CaO>Fe₂O₃>Al2O₃.The emulsifier solution system interface model in the diffusion of aggregate surface chemical composition is relatively significant.In particular,the hydrophilic Na+ and Cl-of the emulsifier do not spread on the surface of Al2O₃ and Fe₂O₃?The results showed that the emulsifier molecules were adsorbed on the surface of these two kinds of chemical components?,and the diffusion of MgO,CaO and SiO₂ on the surface of the two kinds of chemical components is more obvious than that of the first two chemical components.At the same time,the diffusion coefficient is smaller when the emulsifier concentration is higher.At the same concentration condition,the diffusion of CTAC in the chemical composition of emulsifier / aggregate interface was significantly higher than that of SDBS.