Based on the content on this page, looks like I should get to work.

Degradation of cementitious materials

Durability of cementitiouis materials is a key concern in different engineering applications. For example, in radioactive waste repositories, long-term mechanical stability must be ensured for safety purposes. In geological conditions, chemical perturbations can modify the internal structure of these materials, through mineral dissolution and precipitation reactions. Coupled to the evolution of the materials transport properties, these reactions can also generate internal stresses which may lead to the appearance of fractures, further impeding mechanical and transport properties of the materials.

These geochemical perturbations are also likely to appear in other contexts. For example, atmospheric carbonation from CO2 exposure can constitute a stability concern for for engineering systems like dams. Also, offshore wind turbine concrete foundations can also be chemically degraded.

My research work on this topic aims at providing a better representation of the degradation of cementitious materials. Despite being focused in the context of radioative waste repositories, generalization of the methodology can be applied to other engineered systems.

Since 2021, I have been involved in the work package MAGIC from the European Project EURAD, to work on numerical approaches to accurately represent chemo-mechanical coupling. We are looking for a postdoc!

Reactive transport in evolving porous media

Fluid-rock interactions result from the coupled movement of fluid, dissolved species and chemical interactions at the water-rock surface. Description of these processes rely on parameters to characterize each of them. For fluid flow and solute transport, these parameters are the porous medium permeability and pore structure. Geochemical reactions depend on temperature and on the reactive surface area, i.e. contact surface between fluid and the reacting mineral. Through time, these parameters are prone to evolve. The extent of these evolutions strongly depends on the characteristic times of and impacts of each of these interactions. Applications of reactive transport modelling to applications subject to these evolutions thus require accurate and physical description of how the relevant parameters change (a topic treated in this publication). The two main evolutions are:

• Transport parameters (permeability, diffusion), until potential clogging

• Chemical passivation (reduction of reactivity)

In general, these parameters evolutions are taken into account through the use of empirical feedback laws, supposed to upscale the small-scale behavior into averaged bulk-parameters.

Recently, I've had the opportunity to work with Catherine Noiriel on understanding the link between clogging and heterogeneous reactive surface area within fractured porous media. Here below are two figures showing the evolution of an anisotropic porous media subject to the injection (from the top) of a supersaturated fluid.

Acid mine drainage

Open-pit mines tend to produce a lot waste material, called waste rock, which are stored on site as large piles. Suddenly subject to atmospheric conditions (oxygen exposure and rain infiltration), these materials become chemically active. Sulfide minerals tend to oxidise in these conditions, with an associated release of sulfuric acid. The generated acidity may lead to the dissolution of other minerals, releasing potentially toxic metals. Due to the downard migration of percolating rain towards the soils, potential groundwater contamination may occur. In order to understand and mitigate these risks, a deep quantitative understanding of the coupled physicochemical processes at stake may be helpful. Numerical simulations using reactive transport modelling can help achieve this goal, provided they are able to describe and parametrize the relevant processes.

To this end, during my postdoc at the University of British Columbia, funded by the Canadian federal project TERRE-NET, I actively participated in this research through the following activities

• Analysis of the scaling phenomena to help bridge the gap between lab experiment and engineering-scale waste rock piles. In collaboration with the great Bas Vriens, with two specific publications in Journal of Contaminant Hydrology (see figure below showing comparison between experimental and simulation results of fluid composition coming out of different waste rock).

• Analysis of the impact of physical and chemical heterogeneity, as a supervision of Katherine Raymond's Master Thesis, which have led to 2 publications.

• Reactive transport modelling of acid rock drainage in non-isothermal conditions, taking into account the cold climate of northern regions of Canada, and the coupled heat release from the oxidation of sulfide minerals. Supervision of the Master Thesis of Xueying Yi.

• Improvement of numerical algorithms to represent coupled processes by implementing a compositional approach within the reactive transport simulator MIN3P. Publication in 2021.

Uranium exploitation through In Situ Recovery

Need of natural ressources (metals, oil, gas, ...) requires some form of mining. Besides the abovementioned environmental risks, traditional open-pit mines are associated with important geotechnical risks, with the disastrous examples of Mount Polley (Canada, 2014), a copper and gold mine in Chile (2010), Brazil (Iron mine in 2015, dam in 2019). More recently, In Situ Recovery techniques offer a safer mining alternative. For Uranium, In Situ Recovery (ISR) or In Situ Leaching has become a common approach for Uranium production in the world.

Reactive transport modelling can be used to help predict production and environmental impact during Uranium In Situ Recovery (see this awesome publication by the great Vincent Lagneau). In this field, my research focuses on:

• understanding and predicting the environmental impact of an In Situ Recovery exploitation, through a collaboration with a postdoc

• understanding the physico-chemical mechanisms which lead to production wells to clog (related to the PhD of Maelle Vergnaud, as well as with the research projects of Guillaume de Rochefort and Fermin Astigarraga