Guest-ion incorporation in alite and belite structure by NMR experiments and density functional theory calculations

Solid-state MAS NMR spectroscopy and Density Functional Theory (DFT) calculations are shown to be unique experimental and theoretical tools to obtain information about site preferences and guest-ion substitution schemes in the principal phases of Portland cement. For the coupled substitution of Al3+ and F- ions in the silicate phases of a white Portland cement it is found that the fluoride ions are exclusively incorporated in the alite phase by substitution for the interstitial oxygen atoms only. 31P MAS NMR experiments reveal that phosphorus in Portland cements is incorporated by replacement of (SiO4)4- tetrahedra by (PO4)3- units in both alite and belite.

Author: T.T. Tran, S.L. Poulsen, B. Jansang, D. Herfort, H.J. Jakobsen, J. Skibsted

Section: Science and production

Keywords: alite; belite; guest-ion; substitution of ions; NMR spectroscopy; Density Functional Theory