Ph.D. student Position -MISCEA thesis offer ESR14 – Durability of low-carbon concretes: experimental study and modelling of carbonation and chloride diffusion

Two main strategies have been adopted to deal with climate change: mitigation and adaptation. Mitigation focuses on reducing greenhouse gas (GHG) emissions, while adaptation involves preparing for and managing the consequences of a changing climate. In the context of mitigation, the construction industry plays a key role, accounting for around 8% of global CO2 emissions, largely due to cement production. It is therefore essential to develop innovative approaches to reduce the sector’s carbon footprint. 

The adoption of low-carbon concretes is a promising way of reducing the sector’s emissions. These materials use alternative binders, supplementary cementitious materials and optimised mix designs to significantly reduce the embodied carbon in concrete while retaining its essential mechanical and functional properties. However, the transition to low-carbon concretes must be accompanied by a thorough understanding of their long-term performance and durability under a range of environmental conditions. 

Improving the durability of concrete structures is another essential way of reducing CO2 emissions. Durable structures require fewer repairs and replacements, reducing the frequency of resource-intensive construction activities. The intersection of these two objectives – developing low-carbon concretes and ensuring their durability – offers a holistic approach to reducing the environmental impact of the construction industry. This research proposal aims to bridge these two key areas by investigating the durability of low-carbon concrete structures. By examining the mechanisms that govern their performance over time, this study aims to provide scientific information and practical solutions for the sustainable development of the built environment. 

The study will focus in particular on carbonation phenomena and the diffusion of chloride ions in low-carbon concrete. It will be based on three combined approaches: 1- experimental characterisation at laboratory scale, 2- analysis and study at structural scale, 3- numerical simulation at both sample and structural scale. The carbonation of concrete due to the presence of CO2 in the atmosphere and the penetration of chlorides due to the presence of salts in the environment of structures are among the most important phenomena responsible for the lifespan of reinforced concrete structures because of the increased risk of corrosion of the reinforcement. The aim of this research is to better quantify the performance of low-carbon concrete with regard to carbonation and chloride diffusion. This performance-based approach aims to quantify the transport properties and their evolution during the carbonation process (permeability and diffusion coefficient). This subject has four parts: bibliographical, experimental, modelling, simulation and comparison with measurements on structures.

The bibliographic section will review knowledge of transport properties, porosity, pore size distribution and their changes with the degree of carbonation in relation to the nature of the low-carbon binders. It will also review the most recent models of chloride and CO2 penetration, including models of fixation by adsorption and precipitation. Finally, it will include a section on existing low-carbon binders and industry development projects (knowledge on concrete durability).

An experimental component will be carried out in the Egis and Navier laboratories. This will involve producing samples of concrete or mortar based on low-carbon cement (to be chosen from fly ash, slag, geopolymers, calcined clays and limestones, etc.), and carrying out carbonation and chloride diffusion tests. The most important properties will be characterised using appropriate tests: characterisation of the microstructure, permeability and diffusion coefficient measurements and any other parameters that appear necessary. These properties will be quantified on non-carbonated and carbonated materials in order to highlight the major changes during the carbonation process. The experimental part will also be accompanied by carbonation shrinkage tests in order to quantify any mechanical coupling and the risk of induced cracking, which could subsequently be the subject of modelling.

The modelling aspect will include the description of transport equations and behaviour laws, in the general sense, taking into account the non-linear couplings induced by the evolution of the material’s microstructure. The parameters will be calibrated on the basis of literature data or laboratory tests. Finally, the model will be compared with more global measurements (depth of carbonation and chlorides) carried out in the laboratory as part of this project or taken from the literature. The model thus constructed will be numerically implemented in the Bil modelling platform developed in the Navier laboratory and freely available. (https://github.com/Universite-Gustave-Eiffel/bil).

Finally, the simulation and comparison with measurements on structures will be based on Egis’ experience in the field. Existing well-characterised and investigated structures that have been analysed in situ and in the laboratory by Egis will serve as case studies. Numerical simulations of durability with respect to carbonation and/or chloride ion penetration will be carried out using the Bil code in order to compare the model(s) with the reality in the field. Long-term predictions may also be proposed.

Requirements

Research FieldEngineering » Civil engineeringEducation LevelMaster Degree or equivalent

Skills/Qualifications

Master degree or equivalent in civil engineering, materials science or mechanical engineering, numerical simulation and computer programming skillsLanguagesFRENCHLevelExcellent

Additional Information

Eligibility criteria

Description of the project and the candidates’ eligibity criteria :

This position will be part of the EU-funded project MISCEA, which is an ambitious inter- and multidisciplinary Doctoral Training Network under the Horizon-Europe Marie Skłodowska-Curie Actions. 

PhD candidates’ can be of any anationality but you have to meet these eligibity criteria :

• Not being a current employee working at ENPC.
• Not having resided or carried out their main activity (work, studies, etc) in France for more than 12 months during the past 36 months immediately before the deadline of the MISCEA Programme’s call. Compulsory national service, short stays such as holidays and time spent as part of a procedure for obtaining refugee status under the Geneva Convention are not taken into account.
• Holding a Master’s degree (or about to obtain one) or having a University degree equivalent to a European Master’s degree (5-year duration) at the deadline of the MISCEA Programme’s call.
• Researchers must be doctoral candidates, i.e. not already in possession of a doctoral degree at the deadline of the co-funded programme’s call. Researchers who have successfully defended their doctoral thesis but who have not yet formally been awarded the doctoral degree will NOT be considered eligible.
• Signing a declaration of the veracity of the information provided (Declaration of honour, free of form).

If you comply with the eligibility criteria and you wish to submit your application, you must :

• Contact the thesis supervisor and explain your thesis project to her/him so that she/he validates your application.
• Submit a 5-pages thesis proposal under the proposed research areas, with the agreement of the future supervisor. Additionally, to the submission of the 5-pages thesis proposal, the applicant will have to complete an ethics checklist based on ethics guidance from the HorizonEurope programme guide.
• English-translated transcripts from the master’s degree or equivalent.
• Any specific requirements of the Doctoral School corresponding to the targeted MISCEA
  fellowship offer.
• English curriculum vitae, including information about the level on English language knowledge.
• A motivation letter. 
• One letter of reference, at least.

Templates are available on the MISCEA website (link).

Then your candidature is complete, please send inquiries to miscea-program@enpc.fr

Additional comments

The present offer of a doctoral contract in France is for a period of three years.

Full-Time employment : estimated monthly brut salary : ~2700euros (estimated monthly net salary before income taxes: ~2100euros)