CAPILLARY WATER MIGRATION IN ROCK - PROCESS AND MATERIAL PROPERTIES EXAMINED BY NMR IMAGING

We report the application of proton nuclear magnetic resonance (NMR) imaging to the measurement of water content distributions in Lepine limestone, a typical constructional stone. The method is used to observe the kinetics of the absorption of water into this material by capillarity. The water content distributions are consistent with the predictions of unsaturated flow theory. The hydraulic diffusivity of Lepine stone is found to be an approximately exponential function of the water content, in agreement with experimental data on other porous materials. The best estimate of the diffusivity function is D(m2 s-1) = 6.3 x 10(-9) exp(4.90theta(r)), where theta(r) is the normalized volumetric water content. The sorptivity estimated from NMR data is in close agreement with the directly measured value (1.00 mm min-1/2). NMR imaging methods appear promising as a non-destructive and rapid laboratory means of determining moisture distributions, especially for the purpose of accurate measurement of the capillary transport properties of porous materials.