Coniferyl-alcohol lignin as a bio-antioxidant for petroleum asphalt: A quantum chemistry based atomistic study

Petroleum asphalt is an important base material for many industrial applications, such as the binding and waterproofing component in road pavements and roof shingles. Being an organic end product of petroleum serving under the general open-to-air conditions, asphalt can lose the desired rheological properties with time due to oxidative hardening or aging that frequently leads to increase in viscosity, separation of components, and loss of cohesion and adhesion, and thereby becomes hardened. A common practice to alleviate asphalt aging today is using different chemical additives or modifiers as antioxidants. The current state of knowledge in asphalt oxidation and antioxidant evaluation is focused on monitoring the degradation in asphalt’s physical properties, mainly the viscosity and ductility, which although satisfying direct engineering needs does not contribute to the fundamental understanding of the aging and anti-aging mechanisms. Within this context, this study was initiated to study the anti-oxidation mechanisms of bio-based additives, using the coniferyl-alcohol lignin as an example, by developing a quantum chemistry based chemophysical environment in which the various chemical reactions among asphalt components, anti-oxidative additive and oxygen, as well as the incurred physical changes can be studied. The techniques of X-ray photoelectron spectroscopy (XPS) was used to prove the validity of the modified and unmodified asphalt models, from which the XPS results showed high agreement to the model predictions.