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.

Maintenance of road infrastructures represents a considerable socio-economic challenge in a context where budgets of asset managers are increasingly restricted. To optimize the maintenance of these infrastructures, it is necessary to develop monitoring and diagnosis methods to estimate reliably their residual lifetime. It is one of the objectives of the French “Road National Observatory - https://www.idrrim.com/ONR/” launched in January 2016 by the representatives of the road infrastructures sector. The MOVEDVDC project aims at the characterization of residual mechanical properties of bituminous materials in base layers, and their evolution over time, two inputs which are necessary to the calculation of pavement lifetime, and pavement maintenance solutions. The important targets are: - To define a methodology for assessing ageing and damage of bituminous materials, based on the analysis of materials sampled on field and on studies on materials aged in laboratory conditions, - To define ageing indicators used for the assessment of materials lifetime, - To propose, form these studies, models to predict mechanical properties of aged materials (in particular complex modulus and fatigue resistance) and their evolution, to be implemented in pavement lifetime calculation. This is an important output for the dissemination of the project. MOVEDVDC complements the National project DVDC (Pavement lifetime – www.dvdc.fr) which is a collaborative research project launched in June 2016, aiming at the development of tools and methods for the evaluation and maintenance of old pavements. The DVDC project brings together nearly forty partners of the road infrastructures sector: private companies, asset managers, research organizations. MOVEDVDC adresses one of the most important technical and scientific challenges identified in the DVDC project, which is the assessment of ageing and damage state of bituminous materials. The research program of MOVEDVDC is structured around 6 main tasks: (i) coordination, (ii) selection and characterization of experimental sites, (iii) analysis of binder behaviour, (iv) analysis of mixture behaviour, (v) modelling and calculation of pavement residual lifetime and (vi) dissemination. It is realized by a consortium constituted of 4 academic organizations (ESTP, IFSTTAR, INSA Strasbourg and University of Limoges) and 4 private companies (Eiffage Infrastructures, Eurovia, Malet, Total), which bring together strong scientific skills, a strong link to the field, and important laboratory testing facilities. Two major outputs are expected from this project, which will constitute important inputs for the establishment of operational technical guidelines shared with all the stakeholders: - A methodology for the characterization of aged and damaged bituminous materials, at binder and mixtures scales, - A new approach for describing the mechanical performance of these aged materials in the calculation of pavement lifetime and design of pavement maintenance solutions. This approach will constitute a contribution for the future guidelines on pavement maintenance which will be a deliverable of the DVDC project. The project will also lead to the development of a more advanced model for the description of the fatigue behaviour of cracked or damaged materials.