Studies on guest-ion incorporation in Portland cement – Part 1
![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](/uploads/images/2013/w300_h200_x400_y295_101535741_83b77fca05.jpg)
![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](/uploads/images/2013/w300_h200_x400_y347_101535710_dec51fbb10.jpg)
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....
