Study On Interfacial Activity Of Anionic Asphalt Emulsifier Based On Molecular Dynamics Simulation

At present,the quality of asphalt emulsifier in China is uneven.Although there are many brands,there are few varieties.In the common road asphalt emulsifiers,there are many problems,such as unstable working performance,incomplete quality control means and defective formula,which are not conducive to road construction.Therefore,in order to improve the performance of road asphalt emulsifier,it is of great practical significance to explore a feasible and reliable emulsifier design scheme.In this paper,based on the molecular dynamics simulation technology,the interfacial activity of emulsifier on the surface of main chemical components of aggregate was studied by means of simulation and experiment.The main chemical components（calcium carbonate,silica）in limestone and basalt and five anionic asphalt emulsifiers（sodium dodecyl benzene sulfonate,sodium dodecyl sulfate,potassium dodecyl sulfate,sodium dodecyl sulfonate,sodium dodecyl diphenyl ether disulfonate）were selected as research objects to explore the interface interaction energy of emulsifier solution on the surface of main chemical components of aggregate The results show that the polar head of benzenesulfonate has the best interfacial activity among five kinds of asphalt emulsifiers,and the amphiphilic water-based polar head（slded）is repelled on the surface of CaCO₃.Through the conductivity test,the adsorption properties of five emulsifiers on the surface of the main chemical components of aggregate were studied,and the linear relationship between the conductivity and the concentration of emulsifier solution was established,which verified the reliability of the simulation test data.The conclusion is as follows:the conductivity of different emulsifier solutions is greatly different,and there is a linear relationship between the conductivity of emulsifier solution and the concentration of solution at a certain concentration The results show that the conductivity of the original solution of emulsifier:G_SDSN>G_SDBS>G_SLDED>G_SDS>G_PDS;the adsorption capacity of emulsifier on the surface of main chemical components of aggregate increases with the increase of concentration,and increases with the increase of solid-liquid ratio;the adsorption capacity of emulsifier on the surface of CaCO₃is lower than that on the surface of electrochemically neutral non-metallic oxide SiO₂;the adsorption capacity of slded emulsifier on the surface of CaCO₃ The results showed that the adsorption capacity of amphiphilic Water Group on the surface of CaCO₃ was much lower than that of the other four emulsifier molecules.The order of emulsifier adsorption capacity on the surface of CaCO₃ was N_SDBS>N_PDS>N_SDS>N_SDSN>N_SLDED.The order of emulsifier adsorption capacity on the surface of SiO₂ was N_SLDED>N_PDS>N_SDBS>N_SDS>N_SDSN.All the results are consistent with the simulation results.Based on the above conclusion,the structure of new asphalt emulsifier was designed by molecular simulation technology,and the optimal molecular structure of emulsifier in this system was explored.The results show that:3-1Φc12s molecular structure has the optimal interfacial activity;when the carbon chain length of anionic asphalt emulsifier sodium dodecylbenzene sulfonate is about 20 carbon atoms,the interfacial interaction energy of emulsifier on the surface of main chemical components of aggregate is the largest;finally,it is determined that the three-dimensional sodium dodecylbenzene sulfonate and the four dimensional sodium dodecylbenzene sulfonate have the optimal interfacial activity Interfacial activity.