Transport properties evolution of cement model system under degradation - Incorporation of a pore-scale approach into reactive transport modelling

Reactive Transport in Evolving Porous Media

“…Chou et al 2012 provides a review of different tortuosity models for unsaturated conditions and concludes that the use of the Millington-Quirk relation overestimates experimental data. Figure 8 depicts tortuosity as a function of porosity based on common relationships for saturated media, some of which are documented in the literature (Maxwell 1881;Petersen 1958;Tomadakis and Sotirchos 1993), while others are variations of Archie's law (Bentz and Garboczi 1991) or represent an exponential dependence on porosity (Mainguy et al 2000;Seigneur et al 2017). It can be observed that tortuosities obtained from the various relationships differ substantially, in particular for low porosities.…”

“…These observations also imply that different materials are affected in distinctive ways, which is inherently related to the initial organization of their pore structure. Materials with a high degree of initial tortuosity, containing small pore throats, will be more sensitive to the effects of precipitation reactions, which was observed both experimentally and in numerical modelling studies (Kutchko et al 2007;Brunet et al 2013;Huber et al 2014;Seigneur et al 2017).…”

“…In some cases, precipitation reactions lead to the self-sealing of fractures (Steefel and Lasaga 1994;Dobson et al 2003b;MacQuarrie and Mayer, 2005;Gherardi et al 2007) or the reinforcement of the solid structure (Bickmore et al 2001;Pfingsten 2002;Jacquemet et al 2012). Similarly, carbonation of cementitious materials under water can lead to a calcite crust forming on the surface of the material (Dauzères et al 2010;Seigneur et al 2017), making the material almost impermeable. Crust formation has also been observed as a result of gypsum precipitation on historical monuments (Dewanckele et al 2012).…”

“…Leaching of cementitious materials has been studied extensively, since dissolution reactions lead to increased diffusion into these materials, enhancing their deterioration. The prediction of degradation depths of these materials strongly depends on which cementation (or exponential) factor (Shao et al 2013) or which feedback law is considered (Seigneur et al 2017;Georget et al 2018). This is due to the fact that dissolution rates of primary minerals are affected by the diffusion of calcium through the degraded layers.…”

“…This is due to the fact that dissolution rates of primary minerals are affected by the diffusion of calcium through the degraded layers. Several reactive transport studies managed to adequately reproduce the extent of measured degradation depths using either Archie's law (Galíndez et al 2006;De Windt and Badreddine, 2007;Chagneau et al 2015;Li et al 2017;Georget et al 2018) or an exponential relation (Mainguy et al 2000;Seigneur et al 2017) to describe tortuosity evolution as a function of changing porosity. However, the choice of the cementation factor n or the exponential factor a differs between the studies in a way that is not straightforward to predict, depending on the conditions and the materials considered.…”