Solid-state NMR spectroscopy represents a strong tool for characterization and structural analysis on the nanoscale of a wide range of diamagnetic, inorganic materials. Nearly all elements in the periodic table have an isotope with a nuclear spin, and a main advantage of the method is the nuclear-spin selectivity where one nuclear spin-isotope (e.g. 1H, 11B, 13C, 19F, 27Al, 29Si, 31P …) is detected at a time. Thus, rather simple NMR spectra can often been achieved for complex cementitious materials, for example reflecting minor constituent phases or guest-ion incorporation in the principal phases. Although, solid-state NMR is a bulk technique, another advantage is its detection of amorphous and crystalline phases in an equal manner, which has paved the way for a widespread use of the method in quantitative investigations. For example, this feature has been utilized in studies of hydration kinetics by determination of the degree of reaction for the principal clinker phases and for supplementary cementitious materials (SCM’s) in Portland cement blends. Moreover, 29Si and 27Al NMR can provide valuable information about the structure and composition of the calcium-silicate-hydrate (C-S-H) phase formed in hydrated Portland cement blends. The presentation will illustrate some of these features by applications of solid-state NMR in the development of sustainable Portland cement blends including calcined clays or alkali-activation of SCM’s. 29Si{27Al} REAPDOR double resonance experiments and 27Al NMR at very high magnetic field (22.3 Tesla) have been used to obtain unambiguous information about Al incorporation in the C-S-H phase of synthesized samples and C-S-H in hydrated cement blends. Degrees of reaction from 29Si NMR have been used in the implementation of hydration kinetics for alite, belite and calcined clays in thermodynamic modelling and in the evaluation of the pozzolanic reactivity for a number of calcined clay materials. Finally, the information obtained from 29Si NMR on the C-S-H structure has been used in combination with other techniques to investigate the relationship between Ca/Si ratio of the C-S-H phase and the compressive strength of C-S-H binders.

Structure and reactivity of Portland cement components and cement blends from solid-state NMR spectroscopy

253rd National Meeting (2017)

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