Rock porosity determination by combination of X-ray computerized tomography with mercury porosimetry
(1997)
Abstract First results are described of coupling of mercury porosimetry with X-ray computerized tomography (CT) as a new combination technique for rock porosity studies. This technique is suitable for rock samples with a pronounced mercury intrusion-extrusion hysteresis and includes CT measurements before and after mercury intrusion. The entrapped portion of mercury, when the pressure after the intrusion into the rock sample is reduced to 0.1 MPa, serves as a contrast agent in the porous network to localize spatial distribution of rock porosity by CT. The results obtained show that the mercury intrusion and therefore the porosity were quite different for the separate mineral phases. Therefore the combination of mercury porosimetry and computer tomography can give 3-D data on mineral-specific porosity distributions with additional pore size information. In contrast to mercury porosimetry as a single method, results of the combination technique with CT represent a direct visualization of porosity variation and do not depend on any special pore network model.
A new method for the physical characterization of rock matrices for use in site investigations of nuclear waste repositories has been developed. The method can provide information needed in the assessment of the performance of the geosphere working as a natural barrier retarding the migration of radionuclides by diffusion into the rock matrix. Most conventional methods for the physical characterization of rocks give only bulk information. The combination of mercury porosimetry and computer tomography can give 3-D data on mineral-specific porosity distributions with additional pore size information. Additionally, limits for mineral-specific internal surface areas can be estimated, which is essential for the assessment of water-rock interaction and reactive interaction with radionuclides (sorption). Results of measurements on granitic rock (granodiorite) from the Baltic shield are discussed and integrated with results by complementary methods.