Studies on guest-ion incorporation in Portland cement – Part 2
![8 27Al MQMAS NMR spectrum (14.09 T, nR = 13.0 kHz) of the modified Portland clinker with the lowest K2O content (i.e., CaSO4/(CaSO4 + K2SO4) = 100 mol%). The spectrum is acquired with the three-pulse z-filter MQMAS pulse sequence [25], shown below the two-dimensional spectrum, employing 1H decoupling in both the evolution (t1) and detection (t2) periods, a 180° (π) and 60° (π/3) pulse for the excitation and conversion of the triple-quantum coherences, respectively, and a relaxation delay of d1 = 2 s. The pr](/uploads/images/2013/w300_h200_x400_y524_101535089_acfa0a89b7.jpg)
Using solid-state NMR spectroscopy allows identification of the incorporation of guest ions in minor components in the phases of Portland cement clinker. In the second part of the article, further examples of possible element characterizations are shown.
4 Aluminum and sulphur guest-ions in alite and belite
Limestone is increasingly being used as an additive to Portland cement [22] where a part of it will react with the hydrating aluminate species, released by dissolution of the calcium aluminate and ferrite phases or the Al3+ guest ions in alite and belite, and form calcium monocarboaluminate hydrate (Ca4Al2(OH)12CO3 · 5H2O). Thus, limestone acts not only as a filler but contributes also to the strength development by the formation of this phase. For traditional mixtures of Portland cement and limestone, the optimum performance is achieved at...
