(204i) Molecular Dynamics Simulations of Biomass-Modified Model Asphalt

Approximately 18 billion tons of asphalt goes into the paving of American roads. Road construction requires large amount of materials as well as huge energy cost, not forgetting the implications of the construction on the environment. Crude oil, a major source of asphalt binder becomes expensive to obtain and refine, thus increasing the cost of road construction material. In order to promote environmental sustainability and reduce construction costs, there is a need to integrate greener materials into the production of asphalt mixtures to design long-lasting asphalt at specific road conditions. Lignin is a class of organic aromatic polymers responsible for the rigidity and strength of plants. In order to design the optimum biomass-modified asphalt, understanding the relationship between the chemical composition, microstructure, and major physical properties of lignin-modified asphalt is important. In this project, molecular dynamics simulations of the lignin and model asphalt mixtures have been carried out. The asphalt model consists of three components: the asphaltene, aromatic, and saturate. The lignin model consists of guaiacyl monomer, guaiacyl dimer, and a 32 unit polymer of interlinked syringyl and guaiacyl units. Major physical properties such as density, viscosity, thermal conductivity, expansion coefficient, and microstructure such as the radial distribution function has been predicted for lignin-asphalt mixtures at different temperatures. Preliminary results show that the presence of lignin increased the densities of the mixture systems towards the experimental density of pure asphalt which is an indication of good mechanical properties. Also, the addition of lignin has an impact on the radial distribution function (RDF) of asphaltene pairs at all the temperatures considered,with the RDF of the resins and saturates remaining unchanged. The self-diffusion coefficient of the molecules decreases with decreasing temperature and molecular weight.