Is there a future for 43Ca nuclear magnetic resonance in cement science?

Abstract

Calcium and silicon are critical components of cement. While ²⁹Si nuclear magnetic resonance (NMR) is widely used in cement science, ⁴³Ca NMR has received comparatively less attention given the experimental challenges associated with it. To investigate the potential of ⁴³Ca NMR in cement research, a density functional theory study was carried out. The study focused on distinct calcium sites within the calcium silicate hydrate (C–S–H) structure. Four unique calcium sites were identified, each predicted to display distinct ⁴³Ca chemical shifts due to differences in their local environments. These findings were used to generate theoretical ⁴³Ca NMR spectra for C–S–H. Furthermore, theoretical ⁴³Ca NMR spectra for the hydration reaction of triclinic tricalcium silicate were developed, illustrating the potential of ⁴³Ca NMR for tracking the hydration process in multiphase systems.