Surface relaxation and chemical exchange in hydrating cement pastes: A two-dimensional NMR relaxation study

Abstract

We report the first nuclear magnetic resonance (NMR) two-dimensional correlation T1-T2 and T2-T2 measurements of hydrating cement pastes. A small but distinct cross peak in the two-dimensional relaxation spectrum provides the first direct evidence of chemical exchange of water between gel and capillary pores occurring over the first 14days of hydration. A correlation of features along the line T1=4T2 provides strong supportive evidence for the surface diffusion model of H1 nuclear spin relaxation in cements and for a multimodal discrete pore size distribution. Differences in detail of the results are reported for white cement paste and white cement paste with added silica fume. Both the method and the theory presented can be applied more widely to other high surface area materials with other reactive surface areas. © 2005 The American Physical Society.