The Influence of bitumen chemical composition and ageing on pavement performance

The quality of road bitumen in asphalt mixtures is one of the most important factors affecting performance of the entire pavement structure during its service. In particular, the type and refining technology of the crude oil are the most significant aspects influencing bitumen properties. As the same time it is still necessary to assess other aspects that contribute to the changes in bitumen properties, such as bitumen aging during asphalt mixing, storage, transportation, laying and a gradually increasing oxidation in asphalt pavement structure during pavement service life. Bitumen originating from different producers and supplied to Lithuanian market satisfies the requirements of European standards concerning the basic physical properties, albeit certain instability processes in bitumen properties can be observed: bitumen is more liquid and less sticky at a laying temperature; reduced cohesion, increased cracking during compaction; reduced adhesion between bitumen and mineral materials; changes in perceptible properties (odour, colour), and others. These observations have led to numerous discussions on the potential ways of improving bitumen quality, selection of proper methods for bitumen quality assessment and determination of the recommended threshold values. The objective of this paper is to demonstrate the effect of bitumen chemical composition and associated structure on asphalt pavement performance. Performance was expressed in terms of susceptibility to rutting measured by the Performance Grade system developed in the US. Based on the results obtained during this experimental study the limit values of bitumen fractional composition were identified.