Spin-Lattice Relaxation of Water in Cement Gels

Abstract

The time evolution of the magnetization relaxation recovery of exchangeable water in ordinary Portland cement and white cement have been studied as functions of the hydration time together with the temperature and Larmor frequency dependence of the proton spin-lattice relaxation rates. The water self-diffusion coefficient was also studied as a function of both the hydration time and the diffusion time. The results show that the exchangeable water relaxes via cross relaxation to the gel protons, which are in turn relaxed via spin diffusion to paramagnetic impurities. The roughness of the gel-water interface and the wide distribution of pore sizes result in a stretched exponential nuclear magnetization relaxation recovery with the exponent reflecting the fractal geometry of the hydrating cement gel.

Relaxation Time Mapping of ShortT*2Nuclei with Single-Point Imaging (SPI) Methods

“…When the average intensity of a 5 ϫ 5 pixel ROI from the mortar was fit to a stretched exponential, we obtained a value of T 1 ϭ 1.32 Ϯ 0.09 ms (␣ ϭ 0.69 Ϯ 0.05) which agrees with the previously stated bulk values. These values are also comparable to the values obtained by Blinc et al (22), and demonstrate the ability of this method to resolve multiexponential T 1 behaviour, even for very short T 1 's. As illustrated schematically in Fig.…”

“…The third phantom was a 10 mm ϫ 10 mm ϫ 25 mm white Portland cement mortar sample. 2 Blinc et al (22) have shown that T 1 in hydrated cementious materials can be described by a stretched exponential, which corresponds to the fractal geometry of the pore structure. Bulk values for the mortar, fit to a stretched exponential, were T 1 ϭ 1.28 Ϯ 0.02 ms (␣ ϭ 0.69 Ϯ 0.05).…”

Surface Induced Spin-Lattice Relaxation of Water in Tricalcium Silicate Gels

“…After 800-900 hrs the magnetization recovery is a stretched exponential plus a component with a larger TY. The onset of the stretched exponen tial behaviour thus takes place at larger hydration times than in OPC samples [5].…”

“…The shortening of the water Tx is assumed to depend on the ratio between the pore surface area and pore volume. The above effect has been recently used for the study of cement hardening [1][2][3][4][5].…”

A remark on nano-particle stability of cement C-S-H gel

“…Some papers [27][28][29][30], based on the nuclear magnetic resonance (NMR), have indicated the fractal nature of C-S-H gel, as does the protoninduced X-ray emission (PIXE) [31] which recorded the fractal dimension of C-S-H gel in good agreement with the values determined by SANS [6] and NMR [32]. There are also some methods utilizing the fractal image analysis of the surface of cement materials.…”