Abstract
A new radiofrequency probe is manufactured for a GARField (Gradient at Right Angles to
Field) 1 H NMR system to measure paste with a water-to-cement ratio of 0.4 and a diameter
of 15 mm. The probe is calibrated and optimised for measuring cement paste. A series
of wetting and drying experiments of cement paste are undertaken, using GARField NMR
allows local measurements to be conducted with high resolution due to its strong static
magnetic field gradient. The wetting experiments were performed on samples pre-dried
at different temperatures, durations and vacuum pressures. The observed data shows a
dynamic porosity as previously seen by Agata Gajewicz-Jaromin [1]. The spatio-temporal
results are found to be sensitive to the drying conditions. Finally, a new transport model is
presented that captures the features of both wetting and drying data. The model describes
that the apparent diffusion coefficient is a function of water concentration and the evolving
pore size distribution.
Proton NMR dispersion T1 curves are acquired using a Fast-field cycling NMR system in
the 0.01-40 MHz range for aqueous paramagnetic ions (Mn2+ , Fe3+ , Cu2+ ), calcium (Ca2+ )
and for de-gassed water. The data is fitted to an improved SBM (Solomon-Bloembergen-
Morgan) model that provides for the first time a quantitative measurement of inner- and
outer- shell distances as well as exchange and rotational time-constants. The time-constants
obtained with the new shell model are in good agreement with experimental data found in
the literature.
A new in-situ NMR system is built. The design of the magnet is based on the design found
in [2]. The new NMR system is intended to be used for cement hydration and strength
development correlation. This study focuses on the designing, commissioning and testing
of the system. Preliminary results are obtained on rubber, mortar, cement and concrete
samples.