A Method For Measuring Intrusion into Cementitious Materials Containing Paramagnetic Substances Using MicroCT with Contrast Agent

Abstract

A METHOD FOR MEASURING INTRUSION INTO CEMENTITIOUS MATERIALS CONTAINING PARAMAGNETIC SUBSTANCES USING µCT WITH CONTRAST AGENT

PATRICK MICHAEL MARINE

Thesis under the direction of Professor Michael Stabin ,Professor David S. Kosson The intrusion of ions and water into cementitious products can lead to damage through multiple mechanisms. It is thus desirable to know the rate of intrusion of substances into cementitious materials in order to better predict long term performance. One area where this intrusion information is especially important is radioactive waste containment which utilizes steel reinforced concrete, cementitious barriers and cement-based waste forms. Nuclear magnetic resonance imaging and measurement techniques (NMR) have previously been used to measure intrusion into low iron content cementitious materials but this method suffers from paramagnetic induced dephasing when used on high iron content cementitious materials. Since the cementitious materials used in nuclear waste management are often high in paramagnetic materials such as iron oxides, magnesium and nickel, nuclear magnetic resonance methods are less desirable in this application. This work presents the development and application of a novel technique for examining water and ion intrusion into cementitious materials containing significant quantities of paramagnetic substances by utilizing µCT with a contrast agent to improve image quality and enhance intrusion tracking. Intrusion depth at a given time was determined by plotting profiles of linear attenuation coefficients over the entire sample length, and fitting a regression line to the profiles that extended to the sample baseline.