April 1, 2021: PhD public defense – Saeid Babaei – A Multiscale Approach to Model Thermo-Hydro-Mechanical Behaviour of non-reinforced Concrete - UAntwerpen

Name: Saeid Babaei

Date: April 1, 2021 - 14h CET

This is an online event.

A Multiscale Approach to Model Thermo-Hydro-Mechanical Behaviour of non-reinforced Concrete

Cementitious materials are the main pillar of modern construction and urbanization. With their endless practical applications and diversity of utilization from small village houses to skyscrapers, power plants and even nuclear waste disposal structures, they can be seen everywhere. The main driver for this study was to investigate the thermo-hydro-mechanical (THM) behaviour of cementitious engineered barriers, in particular, the barrier for high level nuclear waste containers considered in the Belgian deep geological disposal program.

The principal objective of this study is to investigate the THM behavior of concrete within a multiscale framework. Meaning that material related parameters and phenomena such as water and heat transport in the concrete are studied in scales lower than what is visually observable by us. This helps us understand how the macro scale (scale that we see normally) is affected by what is happening in lower scales (micro and nano scale) which is where a concrete defers from another one. More importantly, to be able to predict fundamental properties of concrete based on its composition to enable optimization of its design. This, however, cannot be achieved without an in-depth study of phenomena and parameters, which are affecting the macro-behavior of the concrete. Since such barriers are exposed to thermal loading emanating from decay of the high level waste, a range of coupled processes usually referred to as THM processes are involved in their performance. Therefore, this thesis proposes a stepwise, multi-component and multiscale framework to model THM behavior of cementitious materials starting from microstructural modelling by representing microstructure of the material based on its chemical composition and reaction condition (curing, age, temperature, etc.). This modelling tool is then coupled with an algorithmic scheme adapted to convert such microstructure to a representative pore network and simulate transport properties. Regarding the mechanical and thermal properties, including elastic modulus, coefficient of thermal expansion and heat conduction coefficient a micromechanical scheme has been implemented by means of numerical homogenization.

Finally, a multiscale and microstructure-informed THM simulation of an engineered barrier for high level nuclear waste container is carried out, where the material parameters are derived using the aforementioned framework (hydro-mechanical). The main objective of this application is to identify spatial regions of the engineered barrier that are prone to crack formation and propagation due to evolving thermal load and its consequences to hydro-mechanical behaviour of the barrier.

Promotor:

  • Bart Craeye (UAntwerpen)

  • Gunther Steenackers (UAntwerpen)

SCK CEN mentors:
  • Suresh Seetharam (SCK CEN)

  • Arnaud Dizier (SCK CEN)

Click here for a list of obtained PhD degrees.