Search

Electroosmosis (EO) is the transport of a solution in porous materials such as soil, brick, and concrete in response to an applied electric DC field. This phenomenon is well-known for the consolidation of soil in geological engineering. However, there are still debates about whether this technique can be effective in drying masonry walls suffering from rising dampness. In this thesis, we have tried to see if EO is obtainable in bricks and provide a quantitative basis to measure the electroosmotic permeability coefficient. Several theories have been proposed to explain EO. Each of these theories have limitations. A phenomenological approach based on non-equilibrium thermo-dynamics is used in this thesis to calculate the electroosmotic permeability coefficient, covering the sum effects by the characteristics of the samples. Electroosmotic transport of water was obtained in all the investigated bricks. A unique cell equipped with four electrodes (two working electrodes and two reference electrodes) was used to measure the EO coefficients in the bricks. The cell was originally designed to measure EO coefficients in clay, so a new sample holder was developed. The brick specimens were water saturated (under vacuum) before the test. The cell design was designed based on the phenomenological approach and all other gradients (concentration, pH, pressure) than the applied electrical potential gradient were eliminated. This ensured, that the flow of water seen (in capillary tubes attached to the cetup) when applying the potential gradient, could only be due to electroosmosis. Electroosmotic coefficients (in the range of 10-10) were measured in six Danish bricks (new from the factory or sampled at demolition sites), and the bricks were red or yellow as traditional Danish bricks. The phenomenological approach was a suitable tool to measure the electroosmotic permeability coefficient. The electroosmotic flow velocity could not be as