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Description
Sedimentary rocks, besides being a key component in the Earth’s subsurface, serve as natural resources and play a vital role in several geological and engineering applications. They form aquifers, reservoir rocks for underground gas storage and are used for building infrastructure. Their durability is hence a significant variable in predicting and assessing long-term challenges. A key process influencing the durability of sedimentary rock is salt crystallization within the pore space, as it enhances weathering (Desarnaud et al., 2015). Understanding the controlling factors of salt precipitation within a porous medium is hence essential to model their long-term durability and potentially develop new conservation strategies.
Salts are introduced into porous rock as dissolved constituents of fluids which are transported via capillary rise, rainfall, sea spray, etc. These processes constitute multiphase flow within a porous medium, and are hence controlled by a complex interplay between parameters such as mineral content, pore geometry, specific surface area, surface roughness, wettability and pore space connectivity (Blunt, 2017; Mehmani and Prodanović, 2014; Wu et al., 2019). Salt precipitation and dissolution alter surface roughness, connectivity and pore space structure, which further complicates multiphase flow, as the pore space itself becomes an evolving system. Understanding how pore-space properties affect salt dissolution and precipitation is therefore important.
In this work, we investigate how altering pore-space properties impacts fluid dynamics and the resulting salt dissolution and precipitation patterns. We employ commonly used conservation products, such as nano silica and nano calcium hydroxide, to alter the pore structure, connectivity and wettability of porous sedimentary rocks used as natural building stones. The impacts of these modifications on salt migration, precipitation and dissolution in rock cores ~ 6 mm in diameter are then investigated using time-resolved micro-CT experiments conducted at the Ghent University - Centre for X-ray Tomography.
By altering the properties of the pore space via the addition of conservation products, we influence salt crystallization processes and hence weathering. This yields insight into strategies to improve the durability of sedimentary rock, which bears implications for aquifer and reservoir rock permeability and damage reduction in masonry.
Acknowledgement: This project was funded by the Dutch Research Council (NWO) through the BugControl project (project number VI.C.202.074) under the NWO Talent program and by FWO grant G065224N.
| References | Blunt, M. J. (2017). Multiphase Flow in Permeable Media: A Pore-Scale Perspective. In Multiphase Flow in Permeable Media. Cambridge University Press. https://doi.org/10.1017/9781316145098 Desarnaud, J., Derluyn, H., Molari, L., de Miranda, S., Cnudde, V., & Shahidzadeh, N. (2015). Drying of salt contaminated porous media: Effect of primary and secondary nucleation. Journal of Applied Physics, 118(11). https://doi.org/10.1063/1.4930292 Mehmani, A., & Prodanović, M. (2014). The effect of microporosity on transport properties in porous media. Advances in Water Resources, 63, 104–119. https://doi.org/10.1016/j.advwatres.2013.10.009 Wu, Y., Tahmasebi, P., Lin, C., Munawar, M. J., & Cnudde, V. (2019). Effects of micropores on geometric, topological and transport properties of pore systems for low-permeability porous media. Journal of Hydrology, 575, 327–342. https://doi.org/10.1016/j.jhydrol.2019.05.014 |
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| Country | Belgium |
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