Description of the thesis topic

The proposed PhD aims to characterize in situ recycled pavement materials stabilized with bituminous binders using reduced-temperature (foam bitumen) or low-temperature (bitumen emulsion) techniques. In particular, the aim is to study the properties of mixtures resulting from the on-site recycling of bituminous layers with the incorporation of part of the underlying soil, resulting from the deep milling of existing pavement structures (equivalent to “full depth reclamation”). In current formulation methods, these materials are often considered as purely granular media and characterized by Proctor and/or static triaxial tests, or, alternatively, as materials treated with hydraulic binders and subjected to indirect tensile tests.
The PhD objectives include studying the remobilization of aged binder present in recycled asphalt aggregates and monitoring the kinetics of changes in the thermomechanical properties of the final materials produced.
The main stages of the research work consist of:
• an in-depth bibliographic study on in situ stabilization procedures and the mechanisms of interaction between aged and added bitumen when using these techniques
• the characterization of the basic components of the materials, including the extraction and thermomechanical characterization of aged bitumen from asphalt aggregates
• sequential de-coating of recycled materials with characterization of the properties of the different layers in order to study the remobilization of aged binder
• monitoring of the maturation of recycled materials over time and under different environmental conditions, through laboratory tests
The research work will be carried out in collaboration with an industrial partner and will be the subject of regular meetings to assess progress and adjust activities based on the results obtained. Stays at the partner's premises may be required.
In addition to laboratory work, the doctoral student will participate in the activities of the road materials research group and, more generally, in the collective life of the laboratory, including societal transfer and outreach activities.

Work Context

Recruitment is taking place within the LTDS's “Geo-materials and Sustainable Construction” team at ENTPE. The PhD candidate wille be part of the research team on the behavior of road, rail, and airport pavement materials and structures.
he Tribology and System Dynamics Laboratory, Joint Research Unit 5513 of the CNRS, brings together researchers from three institutions: the Ecole Centrale de Lyon, the Ecole Nationale des Ingénieurs de St. Etienne, which has become an internal school of Centrale Lyon, and ENTPE.
Within the LTDS at ENTPE, research is conducted in engineering sciences applied to civil engineering and construction, combining approaches from physics (rheology, thermodynamics, acoustics, light), mechanics (materials, structures, dynamics), and perception (comfort, discomfort, intelligibility).
ENTPE employs 21 researchers with various statuses (ITPE, CR and DR from MTES and CNRS), around ten design engineers, research engineers and post-doctoral students, four technicians and five administrative staff in this field. It also hosts around 30 doctoral students with various statuses (ITPE, doctoral contracts, CIFRE, fellowships, others).
Its researchers work in collaboration with other laboratories in France and abroad, particularly in the context of national, European, and international research programs, as well as in collaborative research projects in partnership with industry. The research activities carried out mainly fall within the themes developed by the following three teams:
• “Geomaterials and Sustainable Construction”: Research focuses on natural and anthropogenic geomaterials (soils, raw and bio-based materials, concrete, bituminous materials, composite materials, etc.) for use in construction. Complex stresses and multi-physical couplings (thermo/hydro/chemo/hygro/electro-mechanical couplings) are taken into account, as well as scientific issues related to energy efficiency in buildings. They also concern civil engineering structures (roads, tunnels, embankments, dykes, earthworks, masonry structures, etc.) with the aim of understanding their specific pathologies, rehabilitating them or defining innovative and sustainable construction methods, and proposing advanced design tools.
• “Dynamics of Complex Systems”: Research focuses on model reduction in linear and nonlinear dynamics, developed within a framework of mechanics, applied mathematics, and physical sciences for engineers.
• “Bioengineering & Perception, Materials Mechanics and Processes”: The aim is to develop knowledge about the physics and perception of buildings and their environment, particularly in the fields of acoustics, light, thermal properties and air quality.

The position is located in a sector under the protection of scientific and technical potential (PPST), and therefore requires, in accordance with the regulations, that your arrival is authorized by the competent authority of the MESR.