Linking NANOstructure and macroscopic properties of bitumen to improve their recyclability and ageing: towards a sustainable development of ROAD materials – NANOROAD

Bitumen is a complex viscoelastic compound sensitive to its environment. Upon ageing on roads its viscosity increases and its chemical composition is significantly modified. As a consequence, the inclusion of old asphalts, strongly encouraged for sustainable development issues, has a detrimental impact on final mechanical properties of recycled asphalt materials. In order to technically support and promote this growing addition of aged pavements without decreasing the durability of the road structure, the choice of additives and neat bitumen is crucial because the good adequation of additives with old and new bitumen depends mainly on the nano-structure of the aged bitumen. Therefore, a focus on the nano-structural modification of bitumens in order to better understand the ageing mechanism and the subsequent loss of viscoelasticity is clearly needed. To address the objectives of the project, we propose new methodologies consisting in an extended investigation on aged and rejuvenated bitumen at the nanoscale, while no destructive sample preparation is needed, using Small-and Ultra Small-Angle X-Ray Diffusion (SAXS and USAXS) spectroscopies along with High Resolution Transmission Electron (HRTEM) and Atomic Force (AFM) microscopies. It is thus expected to characterize the multi-scaled aggregated structure of the colloidal asphaltene phase at the 0.2-1000nm scale in its bituminous matrix, and its evolution with: a) ageing, b) rejuvenating treatments and c) temperature at the fluid–viscoelastic transition. This nanoscale structure study will be correlated with data arising from methods basically used to characterise the macroscopic mechanical and chemical bitumen properties. To understand and to assess the impact of ageing on the bitumen nanostructure will help the stakeholders and industrial partners to better select their product in a sustainable development way (eco-conception) aimed at reducing the environmental impact of road construction.