1. The Atomic-Level Structure of Cementitious Calcium Aluminate Silicate Hydrate Determined by NMR
- Author
-
Lyndon Emsley and Pinelopi Moutzouri
- Subjects
portland cements ,metakaolin ,spectroscopy ,six-fold coordinated alumnium ,Materials science ,Coordination number ,Aluminate ,si-29 ,al-27 ,chemistry.chemical_element ,Calcium ,c-s-h ,chemistry.chemical_compound ,mas ,enhanced nmr ,Aluminium ,dynamic nuclear-polarization ,dnp ,solid-state nmr ,dnp.mas ,Polarization (electrochemistry) ,c-a-s-h ,QD1-999 ,six-fold coordinated aluminum ,General Medicine ,General Chemistry ,gels ,Silicate ,al ,Chemistry ,chemistry ,Physical chemistry ,Cementitious ,Hydrate - Abstract
We review our recent paper which resolves the long-standing dilemma of the location and nature of the six-fold coordinated aluminum in calcium aluminate silicate hydrate (C-A-S-H) samples. First principles calculations predict that at high Ca:Si and H2O ratios, aluminum is incorporated into the bridging sites of the linear silicate chains and that the stable coordination number is six. We confirm this hypothesis experimentally by one- and two-dimensional dynamic nuclear polarization enhanced 27 Al and 29 Si solid-state NMR experiments in which we correlate the distinctive six-fold coordinated aluminum NMR signal at 5 ppm to 29 Si NMR signals from silicates in C-A-S-H.
- Published
- 2021