Studies on guest-ion incorporation in Portland cement – Part 1

1 19F MAS NMR spectra (7.05 T) of fluoride-mineralized clinkers, modified from a commercial white Portland clinker, acquired using a spinning speed of nR = 10.0 kHz. The clinkers include 0.04 wt. % fluorine (before modification) and 0.23, 0.36, and 0.77 wt. % fluorine after the second burning with an additional amount of CaF2
1 19F MAS NMR spectra (7.05 T) of fluoride-mineralized clinkers, modified from a commercial white Portland clinker, acquired using a spinning speed of nR = 10.0 kHz. The clinkers include 0.04 wt. % fluorine (before modification) and 0.23, 0.36, and 0.77 wt. % fluorine after the second burning with an additional amount of CaF2
2 Radio-frequency pulse sequences for (a) the I → S spin cross-polarization (CP) experiment and (b) the Rotational-Echo DOuble Resonance (REDOR) experiment [21] combined with an initial 19F → 29Si CP step to selectively excite the 29Si spins that are dipolar coupled to 19F. The π/2 and π pulses (typically of the order 5-10 μs) rotate the magnetization by 90° and 180°, respectively, while x and y denote their relative phases. The contact time in the CP sequence is denoted by tCP and is generally of the order 0.5-5 ms
2 Radio-frequency pulse sequences for (a) the I → S spin cross-polarization (CP) experiment and (b) the Rotational-Echo DOuble Resonance (REDOR) experiment [21] combined with an initial 19F → 29Si CP step to selectively excite the 29Si spins that are dipolar coupled to 19F. The π/2 and π pulses (typically of the order 5-10 μs) rotate the magnetization by 90° and 180°, respectively, while x and y denote their relative phases. The contact time in the CP sequence is denoted by tCP and is generally of the order 0.5-5 ms
3 29Si{19F} CP/MAS NMR spectra (7.05 T) for the fluoride-­mineralized clinkers including 0.23, 0.47 and 0.77 wt. % fluorine, recorded with a spinning speed of nR = 3.0 kHz and a Si-F CP contact time of tCP = 2.0 ms
3 29Si{19F} CP/MAS NMR spectra (7.05 T) for the fluoride-­mineralized clinkers including 0.23, 0.47 and 0.77 wt. % fluorine, recorded with a spinning speed of nR = 3.0 kHz and a Si-F CP contact time of tCP = 2.0 ms
4 29Si MAS NMR spectrum (7.05 T, nR = 7.0 kHz) of the fluoride-mineralized Portland cement clinker including 0.32 wt. % fluorine (a). Optimized deconvolution of the spectrum in (b), employing the sub spectra for belite and the monoclinic MIII form of alite shown in (c) and (d), respectively
4 29Si MAS NMR spectrum (7.05 T, nR = 7.0 kHz) of the fluoride-mineralized Portland cement clinker including 0.32 wt. % fluorine (a). Optimized deconvolution of the spectrum in (b), employing the sub spectra for belite and the monoclinic MIII form of alite shown in (c) and (d), respectively
5 (a) 27Al MAS and (b) 27Al {19F} CP/MAS NMR spectra (7.05 T, nR = 5.0 kHz) of the fluoride-mineralized Portland clinker containing 0.77 wt. % fluorine. The asterisks indicate spinning sidebands
5 (a) 27Al MAS and (b) 27Al {19F} CP/MAS NMR spectra (7.05 T, nR = 5.0 kHz) of the fluoride-mineralized Portland clinker containing 0.77 wt. % fluorine. The asterisks indicate spinning sidebands
6 Crystal structure for triclinic Ca3SiO5 [20]. Si(Ob)4 units are shown as blue tetrahedra, interstitial oxygens (Oi) as red spheres, and Ca2+ ions as grey spheres
6 Crystal structure for triclinic Ca3SiO5 [20]. Si(Ob)4 units are shown as blue tetrahedra, interstitial oxygens (Oi) as red spheres, and Ca2+ ions as grey spheres
Left: Crystal structure for alite (Ca3SiO5). Arrows indicate the coupled incorporation of fluoride and aluminium ions
Left: Crystal structure for alite (Ca3SiO5). Arrows indicate the coupled incorporation of fluoride and aluminium ions
Right: 27Al Multiple-Quantum (MQ) MAS NMR spectrum of a sulphur-mineralized Portland cement
Right: 27Al Multiple-Quantum (MQ) MAS NMR spectrum of a sulphur-mineralized Portland cement

Solid-state NMR spectroscopy is a valuable tool for detection and structural characterization of minor elements incorporated in the principal phases of Portland cement. Depending on the arrangement of these guest-ions, the physical and chemical properties of the materials can be influenced. Part 1 of this article shows the experimental research methods and details.

1 Introduction

Nuclear Magnetic Resonance (NMR) techniques have been increasingly employed in studies of cementitious materials over the last three decades [1-3]. The main advantages of the basic method are the nuclear-spin selectivity, where only one nuclear-spin isotope of the NMR periodic table (for example 1H, 19F, 27Al, 29Si and 35Cl) is detected at a time [2,4], and the fact that the resonances from these spins reflect local structure and/or dynamic effects. Amorphous and crystalline phases are equally detected, thereby complementing diffraction techniques which probe long-range order....
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TEXT Prof. Dr. Jørgen Skibsted1*, Dr. Tine F. Sevelsted1,2, Dr. Søren L. Poulsen1,3 and Dr. Thuan T. Tran1,4

1 Instrument Centre for Solid-State NMR Spectroscopy, Aarhus University, Aarhus/Denmark

2 Conelto ApS, Give/Denmark

3 The Danish Technological Institute, Taastrup/Denmark

4 Aalborg Portland, Cementir Holding, Aalborg/Denmark

*  Correspondance to: jskib@chem.au.dk

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