Characterisation of intra- and inter-C–S–H gel pore water in white cement based on an analysis of NMR signal amplitudes as a function of water content

Abstract

1H nuclear magnetic resonance (NMR) relaxation analysis of water in progressively dried white cement paste is used to estimate the width and relative specific area of intra-C–S–H sheet pores and inter-C–S–H particle gel pores. The measurement is based on the ratio of solid echo to free induction decay signal amplitudes and the observation that as water is removed, so the surface fraction contributing to the solid echo increases. The intra- and inter-C–S–H pores are found to be 1.5 nm and 4.1 nm thick respectively. The total specific area and volume ratio is 2.4 and 0.88 respectively. The volume ratio of readily evaporable water within the pore types is 0.63. Hence, the sheet porosity is 47% of the total or 38% if based solely on evaporable water. The method is distinct from NMR analyses based on the relaxation time. There is good agreement between the measured widths by the two methods.