Open AccessThe Atomic-Level Structure of Cementitious Calcium Aluminate Silicate Hydrate Determined by NMR
Author(s) -
Pinelopi Moutzouri,
Lyndon Emsley
Publication year - 2021
Publication title -
chimia
Language(s) - English
Resource type - Journals
eISSN - 2673-2424
pISSN - 0009-4293
DOI - 10.2533/chimia.2021.272
Subject(s) - aluminate , cementitious , silicate , calcium silicate hydrate , aluminium , hydrate , calcium , chemistry , nuclear magnetic resonance spectroscopy , calcium silicate , mineralogy , materials science , metallurgy , stereochemistry , cement , organic chemistry , composite material
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.