Browsing by Author "Franzoni, Elisa"

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    Electroosmotic permeability in kaolinite and CaCO3 poultice mixtures
    (Journal of Cultural Heritage, 2024) Eslami, Naser; Feijoo, Jorge; Paz-García, Juan M.; Franzoni, Elisa; Ottosen, Lisbeth M.
    Electrokinetic treatment of masonry for desalination or electroosmotic dewatering depends on a poultice, in which the electrodes are placed, which fulfills several purposes. Poultice composed of kaolinite and CaCO3 have been shown to have good workability and high pH buffering capacity. In this work, the elec- troosmotic (EO) permeability is studied in different kaolinite - CaCO3 mixtures. In addition, the effect on EO of using NaCl as a mixing solution is investigated. A special cell is used to test the EO in the speci- mens. A phenomenological approach, based on the potential gradient and the flux of solution, was used to calculate the EO flow rate and EO permeability coefficient. Results showed that by increasing the con- centration of CaCO3 in the poultice mixture, the EO flow rate decreased and the poultice with 80 % CaCO3 and more did not have any EO flow. Furthermore, the ionic strength in the mixing solution decreases the EO flow rate.
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    Experimental study of electroosmosis and (Cl-) diffusion in fired-clay bricks
    (Construction and building materials, 2024) Eslami, Naser; Ottosen, Lisbeth M.; Feijoo, Jorge; Franzoni, Elisa; Paz-García, Juan M.
    Electroosmosis (EO) is considered as a base for methods in drying moist masonry. EO and the other transport mechanisms, namely electromigration and diffusion, that can influence EO in the bricks, were studied in four Danish bricks with different manufacturing years and locations. Brick cubes were cut from each brick type and then saturated in NaCl 0.1 M solution. A cell with four electrodes was used to measure the electroosmotic permeability coefficient using a phenomenological approach based on non-equilibrium thermodynamics. The effective diffusion coefficient for chloride and electromigration coefficient were calculated. Results showed that the EO flux obtained in the bricks did not follow either the magnitude of zeta potential or ionic content present in the bricks. It was observed that there was a correlation between the EO coefficient and the porous structure of the brick, especially with the pore connectivity, since the bricks with higher pore connectivity and, therefore, with higher effective diffusion coefficient had a higher electroosmotic coefficient.
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    Measuring the Electro-osmotic Permeability Coefficient in Single Bricks
    (Journals of materials in civil engineering, 2024) Eslami, Naser; Feijoo, Jorge; Paz García, Juan M.; Franzoni, Elisa; Ottosen, Lisbeth M.
    The transport process electroosmosis (EO) has been suggested to be used for dewatering damp brick masonry for decades. Still, it is debated whether EO can be obtained in bricks. By use of an advanced EO laboratory cell, this paper reports that an EO flow can be generated in two types of Danish bricks. The electroosmotic permeability coefficient was shown to be dependent on both intrinsic properties of bricks, such as pore size distribution, and extrinsic properties, such as zeta potential. Results showed that the brick with a higher pore volume but with a lower surface charge the EO permeability coefficient is lower.