Degradation behaviors of asphalt by microorganisms in asphalt pavement structure

Pseudomonas and Bacillus are dominant microorganisms to widely distributes in asphalt pavement structure. Microbial degradation leads to asphalt aging, and causes its performance deterioration, reducing the durability of asphalt pavement. To better understand the degradation behaviors of dominant microorganisms on asphalt, and reveals their microbial aging mechanisms on asphalt, the effects of microbial degradation on micromorphology, chemical functional group, component and microstructure of asphalt were discussed. Results indicate that main damages of microbial degradation start from asphalt surface and then permeates into its interior. Microorganisms degrade light components of asphalt as nutrients and decompose them into CO₂ and H₂O through oxidation reactions, but exhibit limited degradation ability to macromolecular components. Microbial degradation causes the content changes of asphalt components, altering the colloidal structure of asphalt. Microorganisms destroy the continuity of asphalt surface and increase surface roughness of asphalt. This study provides a new insight into microbial aging mechanism of asphalt.