Multiscale study on aging process and mechanism of high viscosity Asphalt: Macro-micro experiments and quantum chemical molecular simulation

Abstract

Clarifying the aging mechanism of high viscosity asphalt (HVA) is the prerequisite for ensuring its durability, but there are relatively few studies on the aging mechanism of HVA under coupling effects. The quantum chemical simulation method can be applied to better reveal the mechanism of aging behavior from the molecule perspective compared with macro and micro tests. However, the quantum chemical method has not been applied in the HVA aging study. In this paper, the macro and micro tests were carried out to study the changes of macro properties, functional groups, molecular weight and microstructure of HVA after thermal oxygen aging. Quantum chemical simulation was conducted to analyze the reaction sites, steps and products of styrene–butadienestyrene (SBS) and asphalt components in HVA under the coupling effect of oxygen, water and ultraviolet. The results show that with the aging deepening, the penetration and ductility of HVA decrease, the softening point and complex modulus increase, the high-temperature performance increases and the low-temperature performance decreases. After short-term aging, the cross-linked structure destruction and the SBS degradation dominate, so the HVA viscosity decreases and the phase angle increases. After long-term aging, the polymerization of aromatics and saturates dominates, so the HVA viscosity increases and the phase angle increases. The most easily oxidized site in HVA is the carbon atom at the carbon–carbon bond in SBS molecule, followed by the carbon atom connected with the benzene ring in asphalt. SBS is easier to react with oxygen or water than asphalt, so SBS delays the aging of asphalt in HVA. Under different water content, the aging processes and products of SBS/asphalt components with oxygen/water are different, but the ultraviolet excitation does not change the reaction path. The HVA aging was enhanced with the water content increase or ultraviolet excitation by reducing the energy barrier in reaction.