Influence of interface energy on compatibility between ground tyre rubber and bitumen used in asphalt pavement

Providing sustainable high-performance and low-cost materials is one of the main goals pursued by the road industry. This is the reason why special attention is paid to worn tyre valorisation in the road asphalt. Worn tyres can be crushed to ground tyre rubber (GTR) and mixed with bitumen to improve the pavement performance. However, poor compatibility between GTR and bitumen entails some drawbacks: GTR dispersion in bitumen is not optimum, causing heterogeneity problems and a great instability during hot storage. Interface and adhesion aspects appear to be the main factors governing this compatibility. Developing a method to characterise both GTR and bitumen surfaces is thus crucial. Wetting kinetics measurements are the most suitable to determine the contact angles and surface energy of powders. This article presents the application of this method to characterise GTR and then calculate interface energy between GTR and bitumen. We thus develop a new method to better understand compatibility between GTR and bitumen and to optimise the binder formulations used in the road industry.