Effects of bitumen chemical composition on the mechanical properties of isocyanate-based chemically modified bitumen

The use of isocyanate-based reactive additives to prepare chemically modified bitumen (IMB) offers an efficient solution for producing eco-friendly and high-performance modified bitumen. However, chemical modification is strictly related to the chemical nature of bitumen. To reveal the driving mechanism for the evolution of the IMB performance, four petroleum bitumen with different sources were employed as the base bitumen to prepare the IMBs, and ten performance-related indices were investigated to characterize the macro-properties of the IMBs. The chemical information of the base bitumen was interpreted in terms of the functional groups and chemical fractions. The relationships between the macro- and micro-properties of the IMB were analyzed based on the correlation analysis. It was found that the functional groups on bitumen, such as pyrrole, indole, carbazole, phenol, and carboxylic acid, can react with the –NCO functional groups of the isocyanate additive, which promotes the evolution of bitumen performance. The bitumen chemical fractions of asphaltenes and resins have a predominant effect on the performance of the IMB. Principal component analysis showed that the high-temperature performance indices had the strongest correlation with the chemical properties of the IMB. In combination with the partial least squares regression, a Superpave rutting parameter (G*/sinδ)-based index was proposed to evaluate the chemical modification ability of isocyanate additive. This study offers a reference for understanding the mechanism of isocyanate modification and provides guidance for the application of IMBs.