PhD position at SCK CEN

Title: “Evolution of transport, microstructural and hygro-mechanical properties of cementitious materials subjected to coupled chemical degradation via a multiscale approach”

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Summary: In the Belgian concept of geological disposal of radioactive waste in a clay host rock, concrete tunnel liners play a crucial role in ensuring safety during and after (retrievability) the operational phase of the disposal system. Thus the expectation is that the liners offer mechanical stability at least for several hundreds of years. However, concrete is not in geochemical equilibrium with the surrounding geological environment resulting in a gradual evolution of its physical, chemical and mechanical properties, which may not be desirable from safety point of view. Furthermore, the above, that is, chemically induced degradation of concrete structures are equally applicable for near-surface disposal facilities, where concrete is the primary material of construction. Thus the study of long term chemo-mechanical behaviour of concrete is an important undertaking and will offer extremely valuable input and contribute to the safety of the Belgian geological disposal program. The objective of this PhD is to contribute to an improved understanding of coupled chemo-hygro-mechanical behavior of CEM I blended with silica fume and blast furnace slag (applicable for geological disposal) type concrete. Combined leaching and carbonation are the main degradation processes under consideration. These processes are relevant for both deep geological disposal (Phung et al. 2019), where concrete tunnel liners may potentially be subjected to simultaneous leaching and carbonation (due to high carbonate content in the host rock), as well as near surface disposal applications. The combined process is by no means trivial in that opposing effects may be encountered. For instance, leaching causes an increase in porosity (Phung et al. 2015b) and a decrease in strength, whereas carbonation causes a decrease in porosity (Phung et al. 2015a) and an increase in strength. Yet another example is the clogging of some pores caused by the carbonation, which can lead to a decrease in transport properties, but also cause the formation of fractures due to carbonation shrinkage. These coupled processes may have a significant impact on the mechanical behavior, which requires a multiscale experimental and numerical chemo-mechanics approach to reach a thorough understanding of all aspects of these complex coupled processes.

Job description:

o   You prepare a doctoral thesis, which will be supervised by promotors from University of Lille, France; Ghent University, Belgium and mentors from SCK CEN.

o   The PhD project is jointly funded by SCK CEN and ONDRAF/NIRAS.

o   You conduct research and publish scientific articles related to this PhD research project.

o   You will be part of an international, interdisciplinary team.

o   You will mainly work at SCK CEN in Mol, Belgium and partially work at University of Lille, France, Ghent University, Belgium.

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