Mechanism analysis of Lignin's effect on Asphalt's resistance to moisture damage

The present study investigates the mechanism by which lignin enhances the moisture resistance of asphalt materials, employing a combination of atomic force microscopy (AFM) and molecular simulations. The research aims to understand the changes in surface morphology and adhesion properties of asphalt upon immersion, and elucidate the role of lignin modification in mitigating the reduction of adhesive forces. AFM measurements reveal that lignin-modified asphalt exhibits higher adhesion force after moisture damage, possibly attributable to less nanostructures on the surface of lignin modified asphalt. Molecular dynamics simulations are employed to study the binding energies between lignin and different asphalt constituents. The results demonstrate that lignin exhibits the strongest binding affinity with asphaltene molecules, and also displays significant binding affinity with a specific saturated molecule. Furthermore, diffusion of water molecules on asphalt surfaces is investigated, revealing that lignin-modified asphalt exhibits lower water molecule diffusion coefficients and reduced binding energies. Finally, a spherical water molecule model is employed to analyze the wetting behavior on lignin-modified asphalt surfaces, illustrating the dual mechanism of lignin molecules resisting water molecules and inhibiting the binding of polar molecules within asphalt to water molecules. The findings of this research provide insights into the enhancement of moisture resistance in asphalt materials through lignin modification. The combination of AFM and molecular simulations offers a comprehensive understanding of the morphological and adhesive changes at the nanoscale, as well as the fundamental molecular interactions involved. The results contribute to the development of strategies for designing and engineering asphalt materials with improved resistance to moisture damage.