Natural abundance high field 43Ca solid state NMR in cement science
Igor L. Moudrakovski, Rouhollah Alizadeh and James J. Beaudoin
Phys. Chem. Chem. Phys., 2010 DOI: 10.1039/c000353k
This work is a systematic attempt to determine the possibilities and the limitations of the 43Ca high field solid state NMR in the study of cement-based materials. The low natural abundance (0.135%) and small gyromagnetic ratio of 43Ca present a serious challenge even in a high magnetic field. The NMR spectra of a number of cement compounds of known structure and composition are examined. The spectra of several phases important in cement science, e.g., anhydrous beta di-calcium silicate (-C2S) and tri-calcium (C3S) silicate were obtained for the first time and the relation of spectroscopic and structural parameters is discussed. The method was also applied to the hydrated C3S and synthetic calcium silicate hydrates (C–S–H) of different composition in order to understand the state of calcium and transformations in the structure during hydrolysis. The spectra of hydrated C3S reveals a calcium environment similar to that of the C–S–H samples and 11 Å Tobermorite. These observations support the validity of using layered crystalline C–S–H systems as structural models for the C–S–H that forms in the hydration of Portland cement.