Ageing in modified bitumen using FTIR spectroscopy

TLDR

Modified binders exhibit complex rheology from modifier–binder interactions and ageing, and quantifying these interactions and ageing is essential. The study examined three modified binders and base bitumen under various ageing conditions, tracking chemical changes with FTIR spectroscopy. FTIR spectroscopy was used to monitor the evolution of chemical functionalities during ageing of the binders. Immediately after production, elastomer binders showed only physical interactions, whereas plastomer and crumb rubber binders displayed both physical and chemical interactions; ageing did not alter these interactions but revealed oxidation‑related chemical functionalities, with carbonyl and sulphoxide trends identical while aliphaticity and aromaticity diverged.

Abstract

Modified binders exhibit complex rheological behaviour due to the interaction of the modifiers with the base binder and the manner in which they age during field applications. Quantification of the interaction and the ageing of such modified binders is currently a necessity. In this investigation, three modified binders (elastomer, plastomer, and crumb rubber) and the base bitumen were subjected to different ageing conditions and the evolution of the chemical functionalities during ageing were tracked using FTIR spectroscopy. Analysis of the spectra of modified binders immediately after the production process showed that while the elastomer modified binders exhibited physical interaction, the plastomer and crumb rubber modified binders exhibited physical and chemical interactions. During ageing, there was no subsequent evolution of the interactions and one could only see chemical functionalities related to oxidation. Analysis of the spectra showed that the carbonyl and sulphoxide exhibit identical trends whereas aliphaticity and aromaticity deviate drastically.