Effect of Styrene-Butadiene Rubber on Asphalt Binder Energy at Different Temperatures Based on Molecular Dynamics Simulation

To predict the properties of asphalt binder from a molecular point of view, energy index was introduced into asphalt binder performance analysis. The stability of asphalt binder was evaluated using energy as an indicator. The interaction between styrene-butadiene rubber (SBR) and asphalt binder components was analyzed by simulating the energy change of SBR added to the asphalt binder system. Firstly, molecular models of asphalt binder and SBR-modified asphalt binder (SBRA) were established. The structure of the asphalt binder and SBRA systems at room temperature during the pre-structural optimization were analyzed using molecular dynamics simulations and finally based on Materials Studio 8.0. Subsequently, the energies of the output trajectory file at high temperatures (393 K, 413 K, 433 K, 453 K) were analyzed. Finally, the simulation results were verified by macroscopic testing. The results showed that adding SBR did not significantly affect the structure of asphalt binder. However, the addition of SBR improved the energy of asphalt binder at high temperatures. The stability of the SBRA system was optimal at 433 K when the interaction energy between the asphalt binder and SBR was at a maximum. The largest contribution to the interaction energy was van der Waals energy. It is recommended to store SBRA at a temperature of around 433 K during engineering construction. The interaction of the four components of asphalt binder with SBR followed this order: resin-SBR > asphaltene-SBR > aromatic-SBR > saturate-SBR. The higher content of resin and lower content of saturate served to increase the stability between SBR modifier and asphalt binder. The macroscopic test results were consistent with the simulation results, verifying the accuracy of the simulation. Asphalt binder performance can be improved by changing the asphalt binder component content. Analyzing the stability of asphalt binder using energy index provides a new method to study the performance of asphalt binder.