Operando FTIR-ATR with molecular dynamic simulations to understand the diffusion mechanism of waste tire-derived pyrolytic oil for asphalt self-healing

Recent research proves that pyrolytic oils from waste tires are effective in restoring the chemical and rheological properties of aged asphalt binders. Nonetheless, the role of oil-binder molecular interactions and bindeŕs aging degree on the diffusional behavior of the pyro-oils is still unclear. In this study, authors propose integrating operando Fourier Transformed Infrared Spectroscopy (FTIR) measurements with molecular dynamics (MD) simulations as a novel approach to unravel the diffusion mechanisms of pyro-oils in asphalt binders with self-healing purposes. The produced pyro-oils contains aliphatic and single-ring alkyl aromatic compounds as the most abundant species (ca. 80%). The operando FTIR measurements were correlated by a Fickian model, resulting in diffusion coefficients (D₀) between 10^-12 and 10^-11 m²s⁻¹. Moreover, MD simulations, with a molecular model of aged asphalt containing benzylic rings, sulfoxides, and hydroxyl functional groups, demonstrated that interactions of functional groups in the pyro-oil with the binder, hinder the diffusion behavior of the pyro-oil. The D₀ estimated from the MD simulations agreed with those calculated from experimental data and previous reports for petro- and bio-derived rejuvenators. The predictive performance of the MD simulations developed in this study confirms to design of more resilient self-healing asphalt binders using a bottom-up strategy.