Impact of anti-ageing compounds on oxidation ageing kinetics of bitumen by infrared spectroscopy analysis

Abstract

This paper investigates the effect of different anti-ageing compounds (AACs) on the oxidation kinetics of bitumen using Fourier Transformation Infrared (FTIR) spectroscopy. Twenty different AACs were examined, including new and existing AACs for bitumen and polymer products. The AACs were mixed with bitumen to fabricate thin film samples of AAC-modified bitumen which were subjected to laboratory oven ageing at 100 °C with different ageing periods up to 504 h. A Normalized Carbonyl Index (NCI) was proposed based on a selected reference peak (1377 cm−1) to eliminate the impact of the inherent carbonyl content from the bitumen or AACs and manifest the carbonyl growth rate for evaluating the AACs’ anti-ageing performance. It was found the activation energy of fast-term oxidation can be utilized to quantitatively screen the anti-ageing compounds and evaluate their anti-ageing effectiveness in terms of decreasing the formation of carbonyl groups in bitumen. AACs that exhibited high anti-ageing performance were those contained furfural, Irganox acid with sodium montmorillonite, furfural with DLTDP, and high concentrations (e.g., 15%) of Irganox acid. The proposed protocol should be followed by further laboratory rheological and mechanical tests on the AAC-modified bitumen with different binder sources.