23 May 2023
Job InformationOrganisation/Company
INSA de Rennes
Department
Civil Engineering and Urban Planning
Research Field
Engineering » Civil engineering
Researcher Profile
First Stage Researcher (R1)
Country
France
Application Deadline
25 Jun 2023 - 23:59 (Europe/Paris)
Type of Contract
Temporary
Job Status
Full-time
Offer Starting Date
1 Oct 2023
Is the job funded through the EU Research Framework Programme?
Not funded by an EU programme
Is the Job related to staff position within a Research Infrastructure?
No
Offer DescriptionPhD THESIS TITLE : DEVELOPMENT OF SELF-HEALING ECO-MORTARS
Created in 1966, INSA Rennes is a member of the INSA Group, the leading French network of state graduate and post graduate engineering schools, composed of 7 schools in France. Research and innovation are the key elements of INSA, which benefits from the expertise of its 225 professors and lecturers. With six laboratories of international renown, three technological platforms and numerous industrial partners, INSA Rennes stands out for two poles of excellence: Information, Communication Science & Technologies / Materials, Structures & Mechanics. The PhD thesis will take place at the Laboratory of Civil Engineering and Mechanical Engineering (LGCGM: https: // lgcgm.fr) at the National Institute of Applied Sciences of Rennes (INSA Rennes: https: // www. insa-rennes.fr).
CONTEXT
The need to repair concrete structures is nowadays critical as most infrastructures and buildings are counting several decades of service life. One of the main degradations observed on these structures is the steel reinforcement corrosion and the bursting of their concrete coating affecting the structural functionality and leading sometimes to partial ruin. Repairing these damages to recover the initial material performances and to extend the structure service life has a significant cost for the contracting authority. Furthermore, it was estimated by the CONREPNET project that almost 50% of repairs and interventions exhibit signs of failure within five years. Owners indicated that improvements are needed in the way protection and repair of concrete structures are carried out.
The present PhD topic aims to design self-healing eco-mortars to replace defective or contaminated concretes and to protect steel reinforcement. The originality consists in designing a binder coupling several types of mineral additions valorizing local products and industrial by-products, optimizing their performances and durability by introducing novel repair durability indicators. The approach will allow reducing the environmental impact of the repaired structures, but also the repair cost by improving the material lifespan. Indeed, self-healing is best used in a preventive manner, to increase the service life and to reduce the maintenance costs of a repaired structure.
DESCRIPTION OF THE PhD THESIS
The research project aims to design self-healing eco-mortars to replace defective or contaminated concrete protecting the steel reinforcement. The project promotes local products and industrial by-products to design self- healing materials by optimizing their performances and their durability. The research focuses on the hydration process of mineral additions, its optimization to ensure crack healing and the development of repair durability indicators. To achieve these objectives, a multi-scale experimental campaign coupled with numerical modeling will be followed, comprising three parts:
The autogenous healing process will be stimulated using mineral additions. This approach allows limiting the use of cement - whose production rejects an important CO2 content and requires an important energy consumption - and valorizes industrial by-products characterized by latent hydraulic or pozzolanic behavior. The reactions of mineral additions to form new products are generally slow, taking several weeks or months. When a crack appears, unreacted particles are always available to form new products reducing the crack dimensions. Based on these observations, repair mortars with 100% of mineral additions are potential promising candidates to develop a repair material characterized by a lower CO2 footprint and a healing capacity. To design this repair material, several types of mineral additions available in France will be investigated: Blast-Furnace Slag, Fly Ash and Metakaolin. These mixtures are generally regarded as Alkali-Activated Materials as they combine an alkali metal source with a solid silicate powder. A first step in the eco-mortar design is to define a combination of mineral additions (types and content) to satisfy two conditions: an adequate content of unreacted particles available for further reactions to heal the crack, and a compressive strength respecting the strength class of repair materials. In a second step, this autogenous healing process will be coupled with an autonomous healing process thanks to the encapsulation of healing agents. To generate a 3D numerical sample with these different constituents, numerical developments will be carried out on a MATLAB code that it is used today at the Laboratory of Civil Engineering and Mechanical Engineering(LGCGM) to generate 3D porous structures with spherical particles.
In order to limit the cracking risk and to improve the repair durability, the project will introduce durability indicators for repair materials (sound and healed), focusing on the incompatibilities between the repair and its support. More specifically, the delayed deformations (shrinkages, creeps) will be studied at different scales thanks to original experimental means (mechanical tests into a SEM, e.g.). An innovative aspect of the project is the fact that the relaxation capacity will be experimentally determined with tensile creep and relaxation tests. Indeed, the relaxation capacity of hydraulic binders is usually estimated using only compressive creep tests. As the main objective of repair is to provide an adequate protection against the penetration of aggressive agents to concrete, it is also important to correctly assess the transport properties of eco-mortars, particularly the effect of healed cracks. A numerical model will be developed to predict the cracks clogging due to the growth of new solid phases and to determine how the ionic species diffusion are affected by the autogenous and autonomous healing processes. The multiscale numerical model will be used to validate the durability indicator for healed mortars and to estimate the effect of content and size distribution of encapsulated healing agents on effective diffusion coefficient via a numerical parametric study to optimize the mortars design. Finally, a parametric study will be made based on experimentation and numerical modelling to assess the influence of the interface between the repair mortar and the sound concrete. Due to the small thickness of the interface, an asymptotic expansion will be adopted for the numerical model to define a fictive layer to characterize the transport properties.
As one of the main objectives of the project is to develop repair materials respectful of the environment, LCA for several eco-mortars selected as function of their performances will be carried out at the end of the PhD thesis. They will be compared to those of classical repair materials focusing mainly on their global warming potential.
This project is part of the project ANR SHREM (Self-Healing Repair Eco- Mortar) focusing on self-healing repair eco-mortars (https: // lgcgm.fr/recherche/5-materiaux-heterogenes-fluides-et-transfert…).
SUPERVISION
Aveline Darquennes, Full Professor : [email protected]
Mohamed Khaled Bourbatache, Assistant Professor : Mohamed- [email protected]
Kinda Hannawi, Assistant Professor : [email protected]
APPLICATION TERMS
Send your application file by e-mail.
The application file has to contain the following documents:
Research Field
Engineering » Civil engineering
Education Level
Master Degree or equivalent
Research Field
Engineering » Mechanical engineering
Education Level
Master Degree or equivalent
Research Field
Engineering » Materials engineering
Education Level
Master Degree or equivalent
Skills/Qualifications
The applicant has to hold a Master 2, an engineering degree or an equivalent degree in fields related to the subject, e.g., civil and mechanical engineering, materials science, etc.
Knowledge is expected in the field of construction materials, in particular on hydraulic binders. Knowledge on material experimental characterization methods would be also appreciated, as well as skills in numerical modeling (Matlab, Python, Java and Comsol Multiphysics). Knowledge in the field of transport phenomena and chemical reaction would be appreciated. English skills (reading, writing and speaking) are required. The applicant has to be motivated by the subject, curious, rigorous, autonomous and able to take initiatives.
Languages
ENGLISH
Level
Good
Research Field
Engineering » Civil engineering
Number of offers available
1
Company/Institute
INSA Rennes
Country
France
Geofield
Where to applyCity
Rennes
Website
https: // www. insa-rennes.fr/lgcgm
Street
20 Avenue des Buttes de Coësmes
Postal Code
35708 Cedex 7
STATUS: EXPIRED