Study On The Compatibility Between SBS Modifier And Asphalt As Well As The Adhesion Of Modified Asphalt By Molecular Dynamics Simulation

In recent years,since the traffic has been in a trend of rapid development in our country,SBS modified asphalt will be extensively used on the surface of all grades of highways.The compatibility between asphalt and SBS modifier is the guarantee of the modification effect of SBS modifier.However,due to the differences between SBS modifier and asphalt in molecular weight,physical density and chemical structure,SBS modified asphalt will have compatibility problems and a poor thermal storage stability in practical application.Therefore,SBS/asphalt interfacial models,SBS modified asphalt models and SBS modified asphalt/aggregate interfacial models were built by molecular dynamics simulation method in this paper to quantify the compatibility degree of SBS modifier and asphalt and the adsorption degree between SBS modified asphalt and aggregate.It is of great significance to reveal the compatibility mechanism between SBS modifier and how the compatibility mechanism work on the adhesion SBS modified asphalt between aggregate,which can improve the storage stability of SBS modified asphalt and the adhesion between asphalt and aggregate.Firstly,based on the existing theories and researches,the parameters which were better suitable for studying the performance of SBS modified asphalt were proposed.The time step was 1 fs and the periodic boundary conditions were applied to all models.The force field of COMPASS Ⅱ was selected to specify the force field of the atoms.During the simulations,the NVT and NPT ensembles suitable for asphalt simulation were selected,the Andersen temperature control method and the Berendsen pressure control method were used.When coming across the non-bond force,the Atom Based method was applied to calculate the van der Waals non-bonding interaction,and the Ewald method was used to calculate the electrostatic non-bonding interaction.Secondly,the asphalt models,SBS modifier model and aggregate oxide models were constructed.Based on these models,the SBS/asphalt interfacial models,the SBS modified asphalt blend models and SBS modified asphalt/aggregate interfacial models were further constructed.The geometric optimization and annealing process were conducted on these models to get the lowest energy configurations,so as to prepare for the study on the performance of SBS modified asphalt in this paper.The density of the optimized asphalt models was verified,and it is found that the models were suitable for the following simulation.Then,SBS/matrix asphalt interfacial models were first simulated this paper,and the interfacial energy,radial distribution function and relative concentration were taken as the evaluation indexes to study the influence of different preparation temperatures on the compatibility between SBS modifier and asphalt.The results show that the compatibility between SBS modifier and asphalt is better at the preparation temperature of 170 ℃.The simulation results were verified by scanning electron microscope and laser confocal tests.What’s more,the blending models of SBS modified asphalt were studied.The solubility parameters and interaction energy of the system were calculated and the mean square displacement curves of the system were analyzed to evaluate the compatibility between SBS modifier and asphalt at different storage temperatures.Furthermore,the compatible mechanism of the SBS modified asphalt was analyzed.The results show that the compatibility between asphalt and SBS modifier is better at the storage temperature of 160 ℃.Finally,the diffusion of SBS modified asphalt/aggregate interfacial models were simulated.The influence of different temperatures,the kinds of asphalt and aggregates on the adhesion between SBS modified asphalt and aggregate were discussed and the influence of compatibility between SBS modifier and asphalt on the adhesion between SBS modified asphalt and aggregate were also studied.By calculating the interfacial energy and diffusion coefficient of the system and analyzing the mean square displacement and relative concentration distribution of the trajectories of system,the adhesion mechanism between SBS modified asphalt and aggregate was further explained.The results show that the adhesion of different SBS modified asphalts between alkaline aggregate is better,but the influence of temperature and kinds of asphalt on the adhesion do not exhibit a change consistent.By a comprehensive comparison of the influence of temperatures,kinds of asphalt and aggregate on the adhesion between SBS modified asphalt and aggregate,it is found that the type of aggregate is the most important factor,followed by the asphalt types,and the different temperatures have the least effect.