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Title: Broad line NMR imaging : applications to porous building materials and new developments in stray field imaging
Author: Bohris, Alexander J.
ISNI:       0000 0001 3469 0132
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 1999
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A Fourier method of solving the Torrey-Bloch equations for nuclear magnetisation precession in a strong magnetic field gradient has been developed for the purpose of simulating the increasing number of pulse sequences now used in stray field experiments. The simulator explicitly includes the action of the gradient during Rf pulses and the effects of spin relaxation and diffusion. The method has been used to develop a novel one-shot pulse sequence, Dash, for measuring diffusion in the stray field independent of T2 relaxation. Three different strategies to obtain spatially resolved diffusion information using the Dash sequence are presented. It is demonstrated that very high resolution (a few um) diffusion profiles can be obtain with these methods. The results of a magnetic resonance relaxation analysis and broad line magnetic resonance imaging (gradient echo and SPRITE) study of water and water transport in Ordinary Portland Cement Pastes are presented. The effect of varying the cure conditions and the water to cement (w/c) ratio of the sample mix are discussed. Differences in the water transport behaviour between samples dried prior to exposure and non-dried samples are observed. These are particularly evident for 0.3 w/c ratio samples. The water sorptivity and the concentration dependence of the hydraulic diffusion coefficient are calculated for 0.5 and 0.3 w/c ratio samples. An attempt is made to model the experimentally obtained diffusivities using two water transport models found in the literature.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Water uptake; Roofing tiles; Sandstone