The Atomic-Level Structure of Cementitious Calcium Aluminate Silicate Hydrate Determined by NMR


  • Pinelopi Moutzouri Institute of Chemical Sciences and Engineering, EPFL, CH-1015, Lausanne
  • Lyndon Emsley Institute of Chemical Sciences and Engineering, EPFL, CH-1015, Lausanne;, Email:



C-a-s-h, Dnp, Mas, Six-fold coordinated aluminum, Solid-state nmr


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.




How to Cite

P. Moutzouri, L. Emsley, Chimia 2021, 75, 272, DOI: 10.2533/chimia.2021.272.