Fluid imbibition affects almost every activity that directly or indirectly involves porous media, including oil reservoir rocks, soils, building materials, and countless others, including biological materials. In this paper, magnetic resonance imaging MRI has been applied to study water imbibition in a porous medium, in which capillary properties are artificially changed. As a model system, samples of Lecce stone, a material of cultural heritage interest, were analyzed before and after treatment with a protective polymer Silirain-50 or Paraloid PB72. By using MRI, we can visualize the presence of water inside each sample and measure the height zt reached by the wetting front as a function of time during experiments of capillary absorption before and after treatment. The sorptivity S, defined as the initial slope of z versus t1/2, has been determined before treatment and through both treated and untreated faces after treatment. Very good fits to the data were obtained with theoretical and empirical models of absorption kinetics, starting from the Washburn model for capillary rise, adapted by others to homogeneous porous media, and modified by us for application to a sample having a thin low-permeability layer on either surface as a result of a treatment process. This gives us parameters to quantify the effects on imbibition of the changes in the capillary properties. It is known that the Paraloid treatment preferentially affects the larger pore channels and the Silirain the smaller, and our results show this and illustrate the roles played by the different classes of pore sizes.

Models of water imbibition in untreated and treated porous media validated by quantitative magnetic resonance imaging

Mara Camaiti;
2008

Abstract

Fluid imbibition affects almost every activity that directly or indirectly involves porous media, including oil reservoir rocks, soils, building materials, and countless others, including biological materials. In this paper, magnetic resonance imaging MRI has been applied to study water imbibition in a porous medium, in which capillary properties are artificially changed. As a model system, samples of Lecce stone, a material of cultural heritage interest, were analyzed before and after treatment with a protective polymer Silirain-50 or Paraloid PB72. By using MRI, we can visualize the presence of water inside each sample and measure the height zt reached by the wetting front as a function of time during experiments of capillary absorption before and after treatment. The sorptivity S, defined as the initial slope of z versus t1/2, has been determined before treatment and through both treated and untreated faces after treatment. Very good fits to the data were obtained with theoretical and empirical models of absorption kinetics, starting from the Washburn model for capillary rise, adapted by others to homogeneous porous media, and modified by us for application to a sample having a thin low-permeability layer on either surface as a result of a treatment process. This gives us parameters to quantify the effects on imbibition of the changes in the capillary properties. It is known that the Paraloid treatment preferentially affects the larger pore channels and the Silirain the smaller, and our results show this and illustrate the roles played by the different classes of pore sizes.
2008
Istituto per la Conservazione e la Valorizzazione dei Beni Culturali - ICVBC - Sede Sesto Fiorentino
Istituto di Scienze del Patrimonio Culturale - ISPC
Quantitative magnetic resonance imaging
hydrophobic treatments
models of water imbibition
stone conservation
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.14243/119077
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