13C chemical shift anisotropies for carbonate ions in cement minerals and the use of 13C, 27Al and 29Si MAS NMR in studies of Portland cement including limestone additions

Carbonation of C–S–H and C–A–S–H samples studied by 13 C, 27 Al and 29 Si MAS NMR spectroscopy

“…The 13 C MAS NMR spectra (Fig. 8) all include a single resonance at 168 ppm, which originates from the different carbonate ions present in the samples, following our earlier study of Portland-limestone cement pastes [17]. Thus, the different polymorphs of CaCO 3 cannot be distinguished in the present spectra.…”

“…In a recent work, we investigated the potential of 13 C NMR to study carbonate ions in cementitious systems such as Portland-limestone cement pastes [17]. The variation in 13 C chemical shift for carbonate anions was found to be relatively small, preventing a general observation of distinct resonances from structurally different carbonate ions in Portland cement based materials.…”

“…The samples are principally characterized by 29 Si MAS NMR, providing direct knowledge on changes in the silicate chain structure and information about the Ca/Si ratio of the carbonating C-S-H phases. 13 C and 13 C{ 1 H} CP/MAS NMR are used to detect the amount of carbonate ions and the carbonate ions in a hydrous environment, respectively, using the same approach as in our recent 13 C MAS NMR study of the hydration of Portland-limestone cements [17]. Finally, 27 Al MAS NMR is used to follow the structural changes that occur for Al in C-A-S-H phases upon decomposition caused by carbonation.…”

Impact of carbonation on unsaturated water transport properties of cement-based materials

“…29 Si Magic Angle Spinning (MAS) Nuclear Magnetic Resonance (NMR) was used to probe the effect of carbonation on the C-S-H structure as commonly done [45,[48][49][50][51]. We did not use 13 C NMR because it was found difficult to distinguish one calcium carbonate from the others [52]. The 29 Si MAS NMR experiments were conducted following the current protocol of Brunet et al [53].…”

“…Morandeau [12,13] conducted similar experiments using CEM I pastes with or without fly ash (using 10% of CO 2 ). The pore volume of the CEM I pastes was almost uniformly Cement and Concrete Research 74 (2015) [44][45][46][47][48][49][50][51][52][53][54][55][56][57][58] reduced over the whole pore size distribution whereas a significant coarsening was obtained for pastes containing fly ash.…”