Does electro-osmosis work in moisture damage prevention? Applicability of infrared-based methods to verify water distribution under electric fields

In the recent years electro-osmosis drying devices applied to walls in both modern and historic masonry has become one of the leading innovative techniques to prevent damages caused by capillary rising water in building materials. Since the scientific community is raising many doubts on these techniques, the authors aim to propose a fast, simple, noninvasive and economic method to evaluate the dehumidification process specimens of the most used building materials. The paper presents a procedure to monitor water content in different specimens of the most used building materials (e.g. brick, mortar and plaster) and verify any kind of possible effect of electro-osmosis on water diffusion, above all drying kinetic. The procedure is based on the measure of water content and drying behaviour with and without the application of electrostatic fields with the traditional gravimetric method, infrared thermography and optical reflectance in the 940–980 nm with a high sensitivity avalanche photodiode. This allowed us to visualize the surface water content gradient of different building materials. Using different voltage values between tow electrodes coupled with the material under examination, we observed no variation in water distribution inside the material nor any difference in evaporation phenomena. For strong electric field values (V > 150 V/m), compared to those normally used in electro-osmosis dehumidification, we measured mainly the heating caused by the Joule effect due to the intrinsic ion's distribution inside the material.