Determination of moisture profiles in porous building materials by NMR

Because moisture in porous building materials can give rise to several kinds of damage, a detailed knowledge of the moisture transport is essential. for such studies it is important to measure dynamic moisture profiles quantitatively. Nuclear Magnetic Resonance (NMR) offers a powerful technique to measure such profiles in a nondestructive way. Because of the large amount of paramagnetic ions present in many of these materials (0.1-5% Fe) standard NMR imaging equipment cannot be used. A NMR apparatus will be described that was especially developed to study the moisture transport in porous building materials. At the moment, one-dimensional moisture profiles in samples with a diameter of 20 mm can be measured with an accuracy of 1% and a resolution of 1 mm. It takes about 40 s to determine the moisture content at a specific position.