¹H, ²³Na and ³⁵Cl Imaging in Cementitious Materials with NMR

A set-up especially designed for semi-simultaneous measurements of ¹H, ²³Na and ³⁵Cl in ordinary cementitious materials using nuclear magnetic resonance was built. This setup makes use of the main field of a whole body magnetic resonance imaging system (Philips Intera), which has allowed us to combine two measurement setups into one, i.e., a ²³Na/³⁵Cl and a ¹H insert. This 1.5 T field was chosen as a compromise between the signal-to-noise ratio of the spin-echo signal, which increases at higher frequencies, and the line broadening due to the presence of magnetic impurities of these materials, which leads to a decrease of the resolution at higher magnetic fields. The preliminary experiments show that this setup can be used to the study the interaction of different types of ions with cementitious materials. One-dimensional profiles of the moisture and dissolved ions can be measured with a spatial resolution of about 2 mm for ¹H, 6 mm for ²³Na and 9 mm for ³⁵Cl.