Surface magnetic relaxation in porous media is usually attributed to hindered rotation or to paramagnetic impurities on the surface. In cement pastes, however, it seems reasonable to attribute surface relaxation to dipole interactions in water adsorbed as water of hydration on grain surfaces. The rate limiting factor would then be the exchange rate between mobile water in the pores and adsorbed water. The hydrate relaxation time is 17 μs while the measured surface relaxation time is 30-40 μs. This difference is explained if the exchange time between mobile and adsorbed water is about the same as the relaxation time of the water of hydration. The exchange model also suggests that the surface relaxation time should decrease with temperature. Measurements testing this theory are now being prepared.
- Surface relaxation
ASJC Scopus subject areas
- Biomedical Engineering
- Radiology Nuclear Medicine and imaging